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Single-shot quantitative phase microscopy based on color-multiplexed Fourier ptychography

Jiasong Sun, Qian Chen, Jialin Zhang, Yao Fan, and Chao Zuo

Doc ID: 330676 Received 30 Apr 2018; Accepted 18 Jun 2018; Posted 18 Jun 2018  View: PDF

Abstract: We present a single-shot quantitative phase imaging (QPI) method based on color-multiplexed Fourier ptychographic microscopy (FPM). Three light-emitting diode (LED) elements with respective R/G/B channels in a programmable LED array illuminate the specimen simultaneously, providing tri-angle oblique illuminations matching the numerical aperture (NA) of the objective precisely. A single color image sensor records the light transmitted through the specimen, and three monochromatic intensity images at each color channel are then separated and utilized to recover the phase of the specimen. After one-step deconvolution based on the phase contrast transfer function, the obtained initial phase map is further refined by the FPM-based iterative recovery algorithm to overcome pixel-aliasing and improve the phase recovery accuracy. The high-speed, high-throughput QPI capabilities of the proposed approach are demonstrated by imaging Hela cells mitosis in vitro, achieving a half-pitch resolution of 388 nm across a wide FOV of 1.33 mm² at camera-limited frame rates (50 fps).

Reduction of absorption losses in MOVPE-grown AlGaAs Bragg mirrors

Markus Weyers, Garrett Cole, Markus Aspelmeyer, Ute Zeimer, and Johannes Pohl

Doc ID: 330996 Received 08 May 2018; Accepted 17 Jun 2018; Posted 18 Jun 2018  View: PDF

Abstract: Residual p-type doping from carbon has been identified as the root cause of excess absorption losses in GaAs/AlGaAs Bragg mirrors for high-finesse optical cavities when grown by metalorganic vapor phase epitaxy (MOVPE). Through optimization of the growth parameters with the aim of realizing low carbon uptake, we have shown a path for decreasing the parasitic background absorption in these mirrors from 100 ppm to the 10 ppm range near 1064 nm. This significant reduction is realized via compensation of the carbon acceptors by intentional doping with the donor silicon in the upper-most layer pairs of 40-period GaAs/AlGaAs Bragg mirrors. Thus, we find that such compensation enables MOVPE-derived multilayer mirrors with the potential for a high cavity finesse (>100,000 in the near infrared) approaching the performance levels found with Bragg mirrors grown by MBE.

Maintaining broadband gain in Nd3+/Yb3+ co-doped silica fiber amplifier via dual-lasers pumping

Zhiquan Lin, Fan Wang, Meng Wang, Lei Zhang, Suya Feng, Shikai Wang, Chunlei Yu, Lili Hu, and Guojun Gao

Doc ID: 330122 Received 16 May 2018; Accepted 17 Jun 2018; Posted 18 Jun 2018  View: PDF

Abstract: We report a 30-cm-long Nd3+/Yb3+ co-doped silica glass fiber (NYF) amplifier with well-maintained broadband gain through simultaneous dual-lasers pumping at 808 nm and 975 nm. By controlling the ratio of pump power at 975 nm (P975) and 808 nm (P808), the emission band of Yb3+/Nd3+ and energy transfer efficiency of Nd3+→Yb3+ can be well controlled and thus a tunable broadband and flat gain from 1036 nm to 1080 nm are obtained. The theoretical calculation of the energy transfer efficiency of Nd3+→Yb3+ with dual-lasers pumping of 808 nm and 975 nm well explains the mechanism of broadband and flat gain formation in NYF.

Graded-Index Solitons in Multimode Fibers

Amira Ahsan and Govind Agrawal

Doc ID: 331852 Received 17 May 2018; Accepted 16 Jun 2018; Posted 18 Jun 2018  View: PDF

Abstract: We investigate stability of optical solitons in graded-index (GRIN) fibers by solving an effective nonlinear Schr\"odinger equation that includes spatial self-imaging effects through a length-dependent nonlinear parameter. We show that this equation can be reduced to the standard NLS equation for optical pulses whose dispersion length is much longer than the self-imaging period of the GRIN fiber. Numerical simulations are used to reveal that fundamental GRIN solitons as short as 100~fs can form and remain stable over distances exceeding 1~km. Higher-order solitons can also form but they propagate stably over shorter distances. We also discuss the impact of third-order dispersion on a GRIN soliton.

Reconstruction of structured light beams through a multimode fiber based on digital optical phase conjugation

Chaojie Ma, Jianglei Di, yi zhang, Peng Li, Fajun Xiao, Kaihui Liu, Xuedong Bai, and Jianlin Zhao

Doc ID: 332498 Received 27 May 2018; Accepted 16 Jun 2018; Posted 18 Jun 2018  View: PDF

Abstract: Digital optical phase conjugation (DOPC) technique is being actively developed for optical focusing and imaging through or inside complex media. Due to its time-reversal nature, DOPC has been exploited for regenerating different intensity targets. However, whether the targets with three-dimensional information through complex media could be recovered is not experimentally demonstrated. Here, we present a method to regenerate structured light beams based on DOPC. Despite that only the phase of the original scattered wave is time-reversed, the reconstruction of a quasi-Bessel beam and vortex beams through a multimode fiber (MMF) is demonstrated. The regenerated quasi-Bessel beam shows the features of sub-diffraction focusing and a longer depth of field with respect to a Gaussian beam. Moreover, the reconstruction of vortex beams shows the fidelity of DOPC both in amplitude and phase, to the best of our knowledge, which is demonstrated for the first time. We also prove that the reconstruction results of DOPC through the MMF are indeed phase-conjugate to the original targets. We expect that these results could be useful for super-resolution imaging and optical micromanipulation through complex media, and further pave a way for achieving three-dimensional imaging based on DOPC.

All-fiber laser with simultaneous Tm3+ passive Q-switched and Ho3+ gain-switched operation

Baldemar Ibarra-Escamilla, Manuel Duran-Sanchez, Ricardo Alvarez Tamayo, Berenice Posada Ramirez, Patricia Prieto-Cortés, jared alaniz baylon, HECTOR SANTIAGO-HERNANDEZ, Miguel Bello Jiménez, and Evgeny Kuzin

Doc ID: 330968 Received 04 May 2018; Accepted 16 Jun 2018; Posted 18 Jun 2018  View: PDF

Abstract: We experimentally demonstrate simultaneous Tm3+ passive Q-switched and Ho3+ gain-switched operation at 1888.8 and 2021.2 nm in a single cavity all-fiber laser. The passive Q-switch operation of the Tm3+ laser is based on the use of a high concentration holmium-doped fiber as a fiber saturable absorber. Then Tm3+ laser is used as a pump to achieve Ho3+ gain-switched pulses. A Hi-Bi FOLM used as spectral filter allows tuning both Tm3+ and Ho3+ laser emissions.

Generation of 1kHz, 2.3mJ, 88fs, 2.5 μm pulses from a Cr$^{2+}$:ZnSe chirped pulse amplifier

Xiaoming Ren, Lam Mach, Yanchun Yin, Yang Wang, and Zenghu Chang

Doc ID: 332165 Received 21 May 2018; Accepted 15 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: We demonstrate the generation of 2.3 mJ, 88 fs, 2.5 μm laser pulses at 1 kHz repetition rate from a three-stage chirped pulse amplifier employing Cr$^{2+}$:ZnSe crystals as the active gain media. 5 μJ seed of the amplifier is obtained via intrapulse difference frequency generation in a BIBO crystal from spectrally broadened Ti:Sapphire amplifier output. A multi-pass amplifier followed by two single-pass amplifiers pumped by Q-switched Ho:YAG lasers boost the pulse energy to 6.5 mJ, yielding 2.3 mJ, 88 fs pulses upon pulse compression. Our results show the highest peak power at 2.5 μm with 1 kHz repetition rate. Such laser will be a powerful source for studying strong field physics and extending high harmonic generation towards the keV region.

Few-layer TiSe2 as saturable absorber for nanosecond pulse generation in 2.95-μm bulk laser

hongkun nie, Xiaoli Sun, Baitao Zhang, Bingzheng Yan, Guoru Li, yiran wang, Junting Liu, bing nan shi, shande Liu, and Jingliang He

Doc ID: 332402 Received 24 May 2018; Accepted 15 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: 1T-phase titanium diselenide (1T-TiSe2), a model two-dimensional (2D) transition-metal dichalcogenide, has attracted much attention due to its intriguing electrical and optical properties. In this work, a 1T-TiSe2-based high–quality large-area saturable absorber (SA) (1T-TiSe2-SA) was successfully fabricated with the liquid-phase exfoliation method. With the as prepared 1T-TiSe2-SA, a stable, passively Q-switched laser operating at 2.95 μm was firstly realized. Under an absorbed pump power of 3.35 W, the maximum average output-power was 130 mW with a slope efficiency of 5%. A pulse width of 160.5 ns was obtained, which is the shortest among 3.0-µm passively Q-switched lasers ever achieved with 2D materials as SAs. The results indicate that 1T-TiSe2 is a promising alternative as a nonlinear optical modulator for short-pulse laser generation near the 3.0-μm mid-infrared region.

115 W fiber laser with all solid-structure and large-mode-area multicore fiber

Junhua Ji, Raghuraman Sidharthan, Xiaosheng Huang, Jichao Zang, Daryl Ho, Yanyan Zhou, Yehuda Benudiz, Udi Ami, Amiel Ishaaya, and Seongwoo Yoo

Doc ID: 330697 Received 01 May 2018; Accepted 15 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: We investigate mode area scaling by means of supermode operation in an all-solid multicore fiber. To obtain a large mode area, we designed and fabricated an active double- clad multicore fiber, where each Ytterbium-doped core is 19 µm in diameter and has a numerical aperture of 0.067, comparable to the core of the largest available commercial large-mode-area (LMA) fibers. Such six large cores are stacked tightly in a ring structure to enable phase locking of the core fields and supermode operation. The fiber laser performance was investigated in a linear laser cavity with an external Talbot resonator for mode selection. The highest output power achieved was 115 W with an overall 61% slope efficiency corresponding to the pump power. The measured M2 was 1.43 for the central lobe with nearly 70% of the total power. © 2015 Optical Society of America

Coherence lattices in surface plasmon polariton fields

Yahong Chen, Andreas Norrman, Sergey Ponomarenko, and Ari Tapio Friberg

Doc ID: 331122 Received 07 May 2018; Accepted 15 Jun 2018; Posted 18 Jun 2018  View: PDF

Abstract: We explore electromagnetic coherence lattices in planar, polychromatic surface plasmon polariton (SPP) fields. When the SPP constituents are uncorrelated---and thus do not interfere---coherence lattices arise from statistical similarity of the random SPP electromagnetic field. As the SPP correlations become stronger, the coherence lattices fade away, but the lattice structure reemerges in the spectral density of the field. The polarization states of the structured SPP lattice fields are also investigated. Controllable plasmonic coherence and spectral density lattices can find applications in nanophotonics, such as nanoparticle manipulation.

Line-tunable Er:GGAG laser

Richard Svejkar, Jan Sulc, Michal Nemec, Pavel Bohacek, Helena Jelinkova, Bohumil Trunda, Lubomír Havlák, Martin Nikl, and Karel Jurek

Doc ID: 332843 Received 28 May 2018; Accepted 14 Jun 2018; Posted 14 Jun 2018  View: PDF

Abstract: In this paper, for the first time a pulse and CW laser based on Er:GGAG active medium emitting laser radiation at 2.8 μm is presented. With the longitudinaldiode pumping the maximal output energy 4.9 mJ and slope efficiency 13.5 % in pulse regime were reached. Using the birefringent MgF₂ plate the line tunability of Er:GGAG at several spectral bands 2800 – 2822 nm, 2829 – 2891 nm, and 2917 – 2942 nm were obtained.

Controlling attosecond transient absorption with tunable, non-commensurate light fields

Nathan Harkema, Jens Baekhoj, Chen-Ting Liao, Mette Gaarde, Kenneth Schafer, and Arvinder Sandhu

Doc ID: 329031 Received 22 Apr 2018; Accepted 13 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: We demonstrate a transient absorption scheme that uses a fixed-spectrum attosecond pulse train in conjunction with a tunable probe laser to access a wide range of nonlinear light-atom interactions. We exhibit control over the time-dependent Autler-Townes splitting of the 1s4p absorption line in helium, and study its evolution from a resonant doublet to a light-induced sideband with changing probe wavelength. The non-commensurate probe also allows for the background-free study of two-IR-photon emission processes in a collinear geometry. Using this capability, we observe two different emission pathways with non-trivial delay dependencies, one prompt and the other delayed. We identify the nonlinear processes underlying these emissions by comparing the experimental results to calculations based on the time-dependent Schroedinger equation.

Interplay between multiple scattering and opticalnonlinearity in liquid crystals

Alessandro Alberucci, Jisha Pannian, Serena Bolis, Jeroen Beeckman, and Stefan Nolte

Doc ID: 330645 Received 02 May 2018; Accepted 13 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: We discuss the role played by time-dependent scattering on light propagation in liquid crystals. In the linear regime, the effects of the molecular disorder accumulate in propagation, yielding a monotonic decrease in the beam spatial coherence. In the nonlinear case, despite the disorder-imposed Brownian-like motion to the self-guided waves, self-focusing increases the spatial coherence of the beam by inducing spatial localization. Eventually, a strong enhancement in the beam oscillations occurs when power is strong enough to induce self-steering, i.e., in the non-perturbative regime.

Temperature controlling method for optical visualization of fluid flow

Risako Tanigawa, Kenji Ishikawa, Kohei Yatabe, Yasuhiro Oikawa, Takahi Onuma, and Hayato Niwa

Doc ID: 331758 Received 15 May 2018; Accepted 13 Jun 2018; Posted 14 Jun 2018  View: PDF

Abstract: In this Letter, temperature controlling method for optical visualization of fluid flow is proposed. The proposed method enables to visualize invisible fluid flow by controlling the temperature so that its visibility can be easily adjusted. Such ability of adjusting appearance is effective for visualizing the phenomena consisting of multiple physical processes. In order to verify the validity of the proposed method, measurement experiment of visualization of both flow and sound in air using parallel phase-shifting interferometry (PPSI), which is the similar condition to the previous research [K. Ishikawa, Opt. Lett. 43, 991 (2018)], was conducted.

A Novel Ultrafast Smoothing Scheme for Improving Illumination Uniformities of Laser Quads

Zheqiang Zhong, Muyu Yi, Zhan Sui, Xiang Zhang, Bin Zhang, and Xiao Yuan

Doc ID: 319086 Received 01 May 2018; Accepted 13 Jun 2018; Posted 14 Jun 2018  View: PDF

Abstract: The beam smoothing technology, smoothing by spectral dispersion, plays an important role in improving the illumination uniformities of the lasers in inertial confinement fusion facilities. However, due to the limitations of the modulation frequency of the electro-optic modulator, the uniformity of the lasers approaches an asymptotic value after tens of picoseconds that are much longer than the response time of laser plasma instabilities. Here we proposed an ultrafast smoothing approach for improving the uniformities of laser quads. Among the four individual beams in a quad, two of them were smoothed by independently ultrafast focal zooming, and the rest were transformed into Laguerre-Gaussian (LG) beams that carry same topological charges with opposite sign. The focal spots of these two LG beams were coherent superposed and their intensity distributions rotated rapidly in a period of several picoseconds. As a result of the focal zooming and rotation, an ultrafast and significant improvement of the uniformity of a laser quad was achieved. © 2018 Optical Society of America

946 nm Nd:YAG laser with cavity dumping

Alexander Kovyarov, Aleksey Kornev, Vasiliy Pokrovskiy, Yana Fomicheva, Sergey Gagarskiy, and Peter Gnatyuk

Doc ID: 331592 Received 16 May 2018; Accepted 13 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: An end-pumped Nd:YAG 946 nm laser with pulse duration of 1.6 ns, output energy of 2.5 mJ and pulse repetition rate of 50 Hz is described. Such a combination of the parameters achieved has become possible due to the implementation of the cavity dumping mode.

Sparse Representation Based Demosaicing Method for Microgrid Polarimeter Imagery

Junchao Zhang, Luo Haibo, Rongguang Liang, Ashfaq Ahmed, Xiangyue Zhang, Hui Bin, and Chang Zheng

Doc ID: 328604 Received 17 Apr 2018; Accepted 12 Jun 2018; Posted 13 Jun 2018  View: PDF

Abstract: To address the key image interpolation issue in microgrid polarimeters, we propose a machine learning model based on sparse representation. The sparsity and non-local self-similarity priors are used as regularization terms to enhance the stability of interpolation model. Moreover, to make the best of the correlation among different polarization orientations, patches of different polarization channels are joined together to learn adaptive sub-dictionary. Synthetic and real images are used to evaluate the interpolated performance. Experimental results demonstrate that our proposed method achieves state-of-the-art results in terms of quantitative measures and visual quality.

Fluorescent Nanodiamonds for Luminescent Thermometry in the Biological Transparency Window

Masfer Alkahtani, Fahad Alghannam, Linkun Jiang, Arfaan Rampersaud, Robert Brick, Carmen Gomes, Marlan Scully, and Philip Hemmer

Doc ID: 330077 Received 23 Apr 2018; Accepted 11 Jun 2018; Posted 13 Jun 2018  View: PDF

Abstract: Fluorescent nanodiamods (FNDs) have attracted recent interest for biological applications owing to their biocompatibility and photostability (absence of photoblinking and bleaching). For optical thermometry nitrogen-vacancy (NV) color centers and silicon-vacancy (SiV) color centers in diamonds have demonstrated potential, where the NV has the highest sensitivity. However, NV is often excited with green light, which can cause heating and photodamage to tissues, as well as autofluorescence that decreases sensitivity. To overcome these limitations, we report temperature sensing using NV centers excited by deep red light (660 nm) plus another color center that can be excited with NIR light; the nickel (Ni) complex. The NV center measures temperature using diamond lattice expansion while the nickel complex measures temperature using phonon sideband strength.

A simple and efficient NPE mode-locked fiber laser by three-dimensionally manipulating PBS

Jianming Shang, xiaoli lu, Tianwei Jiang, Yueming Lu, and Song Yu

Doc ID: 324843 Received 16 Apr 2018; Accepted 11 Jun 2018; Posted 13 Jun 2018  View: PDF

Abstract: A simple and efficient femtosecond nonlinear polarizationevolution (NPE) mode-locked laser is presented.Different form conventional NPE fiber laser, the polarizationbeam splitter (PBS) is three-dimensionally manipulatedto achieve polarization control and state selectionin our NPE laser. The polarizer, half-wave plateand quarter-wave plate from conventional NPE fiberlasers is replaced by this PBS. Thus, the configurationand the system gain of our proposed laser is simplyand efficiently improved. As a result, transfer efficiencyof 24.17% is experimentally demonstrated. In addition,measured self-started pulses with average power of 49mW and center wavelength of 1584 nm, are generatedwith single pulse energy of 1.51 nJ.

Efficient entanglement generation between exciton-polaritons using shortcuts to adiabaticity

Dionisis Stefanatos and Emmanuel Paspalakis

Doc ID: 332123 Received 18 May 2018; Accepted 11 Jun 2018; Posted 14 Jun 2018  View: PDF

Abstract: We use shortcuts to adiabaticity, a method introduced to speed up adiabatic quantum dynamics, for the efficient generation of entanglement between exciton-polaritons in coupled semiconductor microcavities. A substantial improvement is achieved, compared to a recently proposed method which essentially enhances the nonlinearity of the system. Our method takes advantage of a time-dependent nonlinearity which can become larger than the Josephson coupling between the cavities, while the conventional method is restricted to a constant nonlinearity lower than the coupling. The suggested procedure is expected to find also application in other research areas in optics, where nonlinear interacting bosons are encountered.

Polarization-insensitive hot-electron infrared photodetection by double Schottky junction and multilayer grating

Qiaoping Zhang, Cheng Zhang, linling qin, and Xiaofeng Li

Doc ID: 330511 Received 27 Apr 2018; Accepted 11 Jun 2018; Posted 14 Jun 2018  View: PDF

Abstract: The infrared photodetection based on hot electrons is drawing increasing interests due to the capability in below-bandgap detection, high tunability of working wavelength, compact size, and room-temperature operation. However, the conventional hot-electron photodetectors are mostly based on surface plasmons with a strong polarization preference. In this study, we propose a multilayer-grating double-junction hot-electron photodetector by introducing an ultrathin Au layer sandwiched into two Au-Si-Au cavities. The multilayer grating system allows the excitation of the guided-mode resonance that shows a weak reliance on the incident polarization and therefore realizes the polarization-insensitive optical absorption up to 98%. The special multilayer design facilitates the hot-electron generation in the ultrathin Au layers with a high carrier transport efficiency as well as enables the formation of double Schottky junction, which doubles the carrier emission probability. The optical and electrical benefits ensure a polarization-independent photoresponsivity ~ 1 mA/W at the wavelength of 1470 nm.

Ultra-sensitive spectroscopy of OH radical in high-temperature transient reactions

Shengkai Wang and Ronald Hanson

Doc ID: 331329 Received 10 May 2018; Accepted 11 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: The hydroxyl radical, OH, is arguably the most important transient radical in high-temperature gas-phase combustion reactions, yet it is very difficult to measure because of its high reactivity and thus short lifetime and low concentration. This work reports the development of a novel method for ultra-sensitive, quantitative and μs-resolved detection of OH based on UV Frequency-Modulation Spectroscopy (FMS). To the authors’ knowledge, this is the first FMS demonstration in the near-UV spectral region for detection of short-lived radical species. Shot-noise-limited detection was achieved at an optical power of 25 mW. A proof-of-concept experiment in a tabletop H₂O/He microwave discharge cell has reached a 1-σ Minimum Detectable Absorbance (MDA) of less than 2 × 10^-4 over 1 MHz measurement bandwidth. High-temperature OH measurement was demonstrated in a 15-cm diameter shock tube, where a typical MDA of 3.0 × 10^-4 was achieved at 1330 K, 0.38 atm and 1 MHz. These preliminary results have outperformed the previous best MDA by more than a factor of 3; further improvement by another order of magnitude is anticipated following strategies outlined at the end of this paper. The current method paves the path to ppb-level OH detection capability, and offers prospects to significantly advance fundamental combustion research by enabling direct observation of OH formation and scavenging kinetics during key stages of fuel oxidation that were inaccessible with previous methods.

Endoscopic Diffraction Phase Microscopy (eDPM)

Chenfei Hu, shuaishuai zhu, Gao Liang, and Gabriel Popescu

Doc ID: 334553 Received 05 Jun 2018; Accepted 11 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: In this Letter, we present, to our knowledge, the first endoscopic Diffraction Phase Microscopy (eDPM) system. This instrument consists of a GRIN–lens-based endoscope probe followed by a DPM module, which enables single-shot phase imaging at a single cell level resolution. Using the phase information provided by eDPM, we show that the geometric aberrations associated with the endoscope can be reduced by digitally applying a spectral phase filter to the raw data. The filter function is a linear combination of polynomials with weighting optimized to improve resolution. We validate the principle of the proposed method using reflective semiconductor samples and blood cells. This research extends the current scope of QPI applications, and proves its potentials for future in vivo studies.

High-resolution slow-light fiber Bragg grating temperature sensor with phase-sensitive detection

Arushi Arora, Mina Esmaeelpour, Martin Bernier, and Michel Digonnet

Doc ID: 326317 Received 19 Apr 2018; Accepted 09 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: This Letter reports a slow-light fiber Bragg grating (FBG) temperature sensor with a record temperature resolution of ~0.3 m°C/√Hz, a drift of only ~1 m°C over the typical duration of a measurement (~30 s), and negligible self-heating. This sensor is particularly useful for applications requiring the detection of very small temperature changes, such as radiation-balanced lasers and the measurement of small absorptive losses using calorimetry. The sensor performance is demonstrated by measuring the heat generated in a pumped Yb-doped fiber. The sensor is also used to measure the slow-light FBG’s very weak internal absorption loss (0.02 m-1), which is found to be only ~2% of the total loss.

Plasmonic slow light device using superfocusing on a bow-tied metallic waveguide

Takahiro Furuki, Masashi Ota, and Mitsuo Fukuda

Doc ID: 327250 Received 09 Apr 2018; Accepted 09 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: We demonstrate a plasmonic slow light device using super focusing on a bow-tied metallic waveguide that can be fabricated using complementary metal-oxide semiconductor compatible processes. By solving the characteristic equation of a bow-tied metallic waveguide, we confirmed that the group indices increased as the waveguide width decreased and that they could attain over 11.0 in the telecommunication wavelength band. Additionally, we experimentally confirmed using autocorrelation measurement system that the pulse width of the bow-tied metallic waveguide was 8.0-fs longer than that of a ridged metallic waveguide. Therefore, the proposed device will contribute to the realization of all-plasmonic memories and amplifiers.

Time-resolved inline digital holography for study of noncollinear degenerate phase modulation

Nikolai Petrov, Sergey Nalegaev, Andrei Belashov, Igor Shevkunov, Sergey Putilin, Yu-Chih Lin, and Chau-Jern Cheng

Doc ID: 328337 Received 13 Apr 2018; Accepted 08 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: Recent works demonstrated that digital time-resolved holography is the prospective approach to study nonlinear light-matter interaction processes. In this Letter we present a novel straightforward inline holographic approach for studying of degenerate phase modulation induced by inclined collimated pump beam in the isotropic sample. The method is based on a minimization of the difference between experimentally acquired data and simulated in-line holograms obtained from numerical model of pump-probe interaction in optical nonlinear media. Sophisticated experimental data processing algorithm is implemented to provide high sensitivity and signal-to-noise ratio eligible for soft interaction with collimated pump beam.The integral phase shift determined by our method can be used to estimate the nonlinear refractive index and the relaxation time for material with low damage threshold. We validated our approach for the case of soda-lime and BK7 glasses.

Optical sensing in turbid water using multi-dimensional integral imaging

Bahram Javidi, Satoru Komatsu, and Adam Markman

Doc ID: 330380 Received 27 Apr 2018; Accepted 08 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: There are many underwater sensing applications for information optics due to the large bandwidth and parallelism of optics including sensing, imaging, and communication. However, these applications are highly constrained by turbidity in water caused by optical scattering from dissolved and suspended materials. In this paper, we present a novel approach for optical sensing and detection under turbid water using multi-dimensional spatial-temporal domains integral imaging and dedicated signal processing algorithms. An optical signal is encoded using pseudorandom sequences and an image sensor array is used to capture elemental image video sequences of the light propagating through the turbid water. Using the captured information, multidimensional image reconstruction followed by multi-dimensional (x, y, z, t) correlation to detect the source signal is performed. We experimentally demonstrate scenarios in which turbidity causes image sensing and detection to fail, while our proposed multi-dimensional approach enables successful detection under the same turbidity conditions. Statistical and information theoretic performance metrics including Kullback–Leibler divergence distance, ROC and AUC curves, and probabilities of classification errors are measured and compared for various Beer-Lambert law turbidity conditions. To the best of our knowledge, this is the first report of using multi-dimensional integral imaging detection for under water optical applications in turbid conditions.

Dynamic computer-generated nonlinear-optical holograms in non-collinear second harmonic generation process

Haigang Liu, Xiaohui Zhao, Hui Li, Yuanlin Zheng, and Xianfeng Chen

Doc ID: 330633 Received 30 Apr 2018; Accepted 08 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: Nonlinear holography technique is a powerful tool for all-optical switching and manipulation of arbitrary harmonic wave. The common method of realizing such nonlinear holography is by configuring the structure of nonlinear photonic crystals. However, it is a challenge to dynamically tune the harmonic wave pattern. To overcome the long-term existed non-dynamic property of such nonlinear holographs, we realize dynamic computer-generated nonlinear-optical holograms in non-collinear second harmonic generation process, which only one infrared beam is modulated. Arbitrary patterns both in fundamental-frequency and second harmonic waveband can be generated at the same time. This work offers a flexible and dynamic method for arbitrary nonlinear wave-front shaping technology.

Two-dimensional combination of eight ultrashort pulsed beams using a diffractive optic pair

Tong Zhou, Qiang Du, Tyler Sano, Russell wilcox, and Wim Leemans

Doc ID: 331216 Received 21 May 2018; Accepted 08 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: We demonstrate the first two-dimensional diffractive beam combination for ultrashort pulses, a highly scalable technique capable of using a diffractive optic pair to combine large arrays of ultrashort pulsed beams. A square array of eight 120-fs pulsed beams from eight fiber outputs are coherently combined into one beam using the diffractive combiner. Experimental results show the combined pulse preserves input pulse width and shape, and the combining efficiency is measured to be close to the limit of the manufactured diffractive optic. Analysis shows the combining loss due to uncompensated temporal and spatial dispersions is negligible.

Quantum features in the orthogonality of optical modes for structured and plane-wave light

David Andrews and Kayn Forbes

Doc ID: 331420 Received 11 May 2018; Accepted 08 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: A fundamental photon creation-annihilation commutation relation underpins the familiar quantum formulation of optics. However, an internal inconsistency becomes apparent in the pursuit of structured light applications. This requires the relationship between operator commutation and mode orthogonality to be recast in a form ensuring full consistency with the precepts of quantum theory. A suitable reformulation, shown to register correctly an intrinsic quantum uncertainty in the associated interactions, has special relevance to optical vortex physics – particularly with regard to information content – through its connection to the degrees of freedom in the associated radiation modes.

High-temperature stable and sterilizable waveguide Bragg grating in planar cyclo-olefin copolymer

Manuel Rosenberger, Stefan Kefer, Maiko Girschikofsky, Gian-Luca Roth, Steffen Hessler, Bernhard Schmauss, Ralf Hellmann, and Stefan Belle

Doc ID: 330188 Received 27 Apr 2018; Accepted 08 Jun 2018; Posted 13 Jun 2018  View: PDF

Abstract: In this paper, we demonstrate a high-temperature stable polymer planar waveguide Bragg grating based on cyclo-olefin copolymers (COC). The high glass transition temperature of the polymer material amounting to 178 °C in conjunction with a high-temperature stable UV-curable adhesive used to connect the polymer sensor to a standard single-mode fiber, enables temperature readings of up to 160 °C while exhibiting a temperature sensitivity of -7.3 pm/°C. The reflected power of the Bragg wavelength remains constant up to a temperature of 130 °C before declining at higher temperatures with an overall reduction of 2.5 dB at 160 °C. However, decreasing temperature results in a complete recovery of the peak power, facilitating steam pressure sterilization (129 °C, 0.17 MPa) of the polymer planar waveguide Bragg grating.

A high-efficiency and thermal-stable far-red-emitting NaLaMgWO6:Mn4+ phosphor for indoor plant growth LEDs

Xiaoyong Huang, Jia Liang, Bin Li, Liangling Sun, and Jun Lin

Doc ID: 330606 Received 30 Apr 2018; Accepted 07 Jun 2018; Posted 14 Jun 2018  View: PDF

Abstract: In this work, we reported a novel NaLaMgWO6:Mn4+ double-perovskite phosphor. Under excitation at 342 nm, this phosphor showed high-efficiency far-red emission around 700 nm with internal quantum efficiency up to 60%. Moreover, it exhibited high thermal stability; the emission intensity at 4 k was about 57% of that at room temperature. Finally, a prototype light-emitting diode (LED) device was fabricated using the combination of NaLaMgWO6:Mn4+ far-red emitting phosphor and a 365 nm LED chip.

Monolithic integration of III-nitride voltage-controlled light emitters with dual-wavelength photodiodes by selective-area epitaxy

CHAO LIU, Yuefei Cai, Huaxing Jiang, and Kei May Lau

Doc ID: 328589 Received 17 Apr 2018; Accepted 07 Jun 2018; Posted 15 Jun 2018  View: PDF

Abstract: We report for the first time on-chip integration of III-nitride voltage-controlled light emitters with visible and ultraviolet (UV) photodiodes (PDs). InGaN/GaN and AlGaN/GaN heterostructures were grown in specific regions by selective area epitaxy, allowing monolithic integration of versatile devices including visible light emitting diodes (LEDs), visible-light PDs, AlGaN/GaN high electron mobility transistors (HEMTs), and UV-light Schottky barrier (SB) PDs. A serial connection between the LED and HEMT through the epitaxial layers enables a three-terminal voltage-controlled light emitter (HEMT-LED), efficiently converting voltage-controlled signals into visible light signals that can be coupled into an adjacent visible-light PD generating electrical signals. While the integrated blue HEMT-LED and PD transmits signals carried by visible light, the visible-blind SB-PD on chip receives external UV light control signals with negligible interference from the on-chip visible light source. This integration scheme can be extended to open an avenue for developing a variety of applications, such as smart lighting, on-chip optical interconnect, optical wireless communication, and opto-isolators.

Controllable structural tailoring for enhanced luminescence in highly Er3+-doped germanosilicate glasses

Wenqian Cao, Feifei Huang, Zheng Wang, Ruo Lei, ying tian, youjie hua, Huanping Wang, Junjie Zhang, and Shiqing Xu

Doc ID: 331452 Received 10 May 2018; Accepted 07 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: Higher concentrations of rare earth (RE) ions in glass materials would be favorable for the output of single-frequency fiber lasers. In this work, we adjusted the topological structure of glass networks through controlling the numbers of non-bridging oxygens (NBO) and bridging oxygens (BO) by tuning the composition of the glasses, hence increasing the RE doping concentration of germanosilicate glasses. The increased flexibility of the glass networks favors the distribution of clusters of RE ions to decrease fluorescence quenching, which was validated by both our experimental and theoretical results. To the best of our knowledge, for the first time, a highly Er3+-doped (up to 7 mol%) heavy metal oxide glass was fabricated without quenching by tuning the components of the glass. In addition, we have demonstrated an approach to enhance the fluorescence properties of heavily RE-doped glass materials by tailoring network topology.

All-Fiber Frequency-Resolved Optical Gating Pulse Characterization from Chalcogenide Glass

Nurmemet Abdukerim, imtiaz alamgir, and Martin Rochette

Doc ID: 327910 Received 12 Apr 2018; Accepted 07 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: We report the first all-fiber frequency-resolved optical gating (FROG) device from nonlinear processing in chalcogenide glass. The strong four-wave mixing efficiency of an 11 cm long chalcogenide microwire enables a high sensitivity characterization of pulses in the 2 μm wavelength band. The amplitude and phase of chirped and unchirped picosecond pulses are accurately characterized with a high sensitivity of 0.16 mW². This represents more than six orders of magnitude improvement in sensitivity comparing to conventional FROG techniques based on second-harmonic generation.

Low dark-current and high photo-detectivity transparent organic ultraviolet photodetector by using polymer modified ZnO as electron transfer layer

Dan Zhao, MengGe Wu, Ruiheng Qin, and Junsheng Yu

Doc ID: 332192 Received 21 May 2018; Accepted 06 Jun 2018; Posted 07 Jun 2018  View: PDF

Abstract: In this letter, a transparent organic photodetector (OPD) with a property of ultraviolet sensitivity is demonstrated by using an inverted architecture. A conjugated polymer of ploy[(9,9-bis(3’-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctyl)fluorene)] (PFN) is introduced to modify the energy level and morphology between ZnO and organic optoelectronic material. As a result, at a wavelength of 350 nm and a bias of –1 V, the photo-detectivity of 10¹² Jones from both sides of the transparent device is obtained with a working area of 1 cm². Moreover, an optical simulation is applied to analyze the optical electric field distribution inside the OPD.

Photoelectron holography and forward scattering in atomic ionization by elliptically polarized laser pulses

Hui Xie, MIN LI, Siqiang Luo, Yang Li, Jia Tan, Zhou Yueming, Wei Cao, and Peixiang Lu

Doc ID: 331567 Received 15 May 2018; Accepted 06 Jun 2018; Posted 07 Jun 2018  View: PDF

Abstract: We report on the scaling of the photoelectron holography with the laser ellipticity in strong-field atomic ionization. We find that the spacing of the holographic fringe gradually decreases with increasing the ellipticity. In terms of the strong-field approximation, the scaling of the fringe spacing with the laser ellipticity is explained by the effect of the initial transverse momenta at the tunnel exit. With increasing the laser ellipticity, a ridge structure arising from forward scattering electrons is observed in the low energy region of the electron momentum distribution. Analytic formula is obtained that demarcates the phase diagram for the observation of the holographic pattern and ridge structure in elliptically polarized laser fields.

Compact double-part grating coupler for higher-order mode coupling

Yaxiao Lai, Yu Yu, Songnian Fu, Jing Xu, Ping Shum, and Xinliang Zhang

Doc ID: 331645 Received 14 May 2018; Accepted 06 Jun 2018; Posted 07 Jun 2018  View: PDF

Abstract: We propose and demonstrate a compact and efficient grating coupler for first-order mode fiber-to-chip coupling. The coupler is configured by a double-part grating structure combined a curved Y-junction by means of mode diversity. Compared with traditional grating coupler, the designed structure takes advantage of minimizing the taper lengths of gratings, while performing higher coupling efficiency and lower crosstalk. At a mere 20 μm taper length, we measured a peak coupling efficiency of -3.68 dB with a 1-dB bandwidth of 35 nm. The coupling performance for fundamental mode is also investigated. A reduced crosstalk below -15 dB within the whole band with reasonable coupling efficiency can be experimentally observed.

Three-stage frequency conversion of sub-microsecond multiline CO laser pulse in a single ZnGeP₂ crystal

Igor Kinyaevskiy, Andrey Ionin, Yuriy Klimachev, Yury Andreev, and Vera Mozhaeva

Doc ID: 331744 Received 15 May 2018; Accepted 06 Jun 2018; Posted 07 Jun 2018  View: PDF

Abstract: Broadband three-stage frequency conversion of multiline sub-microsecond CO laser radiation in a single sample of ZnGeP2 crystal was experimentally and numerically studied for the first time. As a result, the hybrid laser system emitted more than 200 narrow spectral lines within 2.4-6.2 μm spectral range. The measured conversion efficiencies of the 1st, 2nd and 3rd stages were about 4.8 %, 0.4% and 0.05%, respectively. Our numerical simulation demonstrated that the 3rd stage of this frequency conversion can extend the laser system spectrum toward the shorter wavelength of 2.2 μm.

High-quality partially coherent Bessel beam array generation

Chunhao Liang, Xinlei Zhu, Chengkun Mi, Xiaofeng Peng, Fei Wang, Yangjian Cai, and Sergey Ponomarenko

Doc ID: 331753 Received 15 May 2018; Accepted 05 Jun 2018; Posted 07 Jun 2018  View: PDF

Abstract: We propose a protocol for generating high-quality, partially coherent (quasi-)Bessel beam arrays with controllable beam order and spatial distributions. Our protocol involves, apart from beam intensity shaping, coherence engineering of recently introduced optical coherence lattices. Our theoretical results are validated with the experimental realization of partially coherent Bessel beam arrays. The novel beam arrays are anticipated to be useful for multi-particle trapping and micromanipulation, optical metrology and microscopy as well as for 3D imaging.

Design study of random spectrometers for applications at optical frequencies

Paris Varytis, Dan-Nha Huynh, Wladislaw Hartmann, Wolfram Pernice, and Kurt Busch

Doc ID: 327478 Received 03 Apr 2018; Accepted 05 Jun 2018; Posted 07 Jun 2018  View: PDF

Abstract: Compact spectrometers based on disordered planar waveguides exhibit a rather high resolution with a relatively small footprint as compared to conventional spectrometers. This is achieved by multiple scattering of light which – if properly engineered – significantly enhances the effective optical path length. Here a design study of random spectrometers for TE- and TMpolarized light is presented that combines the results of Mie theory, multiple-scattering theory and full electromagnetic simulations. It is shown that the performance of such random spectrometers depends on single scattering quantities, notably on the overall scattering efficiency and the asymmetry parameter. Further, the study shows that a well-developed diffusive regime is not required in practice and that a standard integrated-optical layout is sufficient to obtain efficient devices even for rather weakly scattering systems consisting of low index inclusions in high-index matrices such as pores in planar silicon-nitride based waveguides. This allows for both significant reductions in footprint with acceptable losses in resolution and for device operation in the visible and near-infrared frequency range.

Enhancing artificial sum frequency generation from graphene-gold metamolecules

Jin Yao, Guoxiong Cai, Na Liu, and Qing Huo Liu

Doc ID: 328633 Received 19 Apr 2018; Accepted 05 Jun 2018; Posted 07 Jun 2018  View: PDF

Abstract: The enhanced artificial sum frequency generation (SFG) is realized by graphene-gold metamolecules at the mid-infrared without any natural nonlinear material. The unit cell of the proposed metamolecules combines an inner graphene cut-wire meta-atom and an outer gold split-ring resonator meta-atom. In order to achieve high efficiency of the artificial SFG, not only the novel material of graphene with high mobility is used as the constituent material, but also the double resonances at two fundamental frequencies are excited to form an intensive magnetic Lorentz force. Both time domain response and frequency domain response are analyzed numerically. Results show that the SFG efficiency is at least 2 orders of magnitude larger than that of second harmonic generation which only involves a single resonance. The tunability of graphene on the SFG is studied as well. This work will facilitate the engineering of nonlinear metamaterials, whose nonlinear properties can be customized by artificially structuring, in their practical applications.

Double inverse nanotapers for efficient light coupling to integrated photonic devices

Junqiu Liu, Arslan Raja, Martin Pfeiffer, Clemens Herkommer, Hairun Guo, Michael Zervas, Michael Geiselmann, and Tobias Kippenberg

Doc ID: 325265 Received 07 Mar 2018; Accepted 05 Jun 2018; Posted 07 Jun 2018  View: PDF

Abstract: Efficient light coupling into integrated photonic devices is of key importance to a wide variety of applications. "Inverse nanotapers" are widely used, in which the waveguide width is reduced to match an incident mode. Here, we demonstrate novel, "double inverse" tapers, in which we reduce both the waveguide height and width. We demonstrate >45% chip-through coupling efficiency for both the TE and TM polarizations in tapers of >500 nm width, in comparison to regular inverse tapers which necessitate <100 nm width. The double inverse tapers show reduced polarization dependent coupling and allow the fabrication using DUV photolithography, relevant for nonlinear photonic applications at near-IR and visible wavelengths, e.g. supercontinuum and soliton micro-comb generation.

Achromatic linear retarder with tunable retardance

ABDELGHAFOUR MESSAADI, Maria del Mar Sanchez-Lopez, Asticio Vargas, Pascuala Garcia-Martinez, and Ignacio Moreno

Doc ID: 332786 Received 29 May 2018; Accepted 05 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: We present a universal design and proof-of-concept of a tunable linear retarder of uniform-wavelength response in a broad spectral range. It consists of two half-wave retarders (HWR) in-between two quarter-wave retarders (QWR), where the uniform retardance can be tuned continuously by simply rotating one of the HWRs. A proof-of-concept of this design is built by using commercially available Fresnel rhomb retarders (FR) that provide retardation with almost wavelength-uniformity in the visible and near infrared from 450 to 1550 nm. The design is universal since other achromatic QWR and HWR could also be employed. The system is experimentally demonstrated to control the state of polarization of a supercontinuum laser.

Weak Plasmon-exciton Coupling between Monolayer MoS2 and Aluminum Disks

Hailong Liu, Bing Zhang, Tian Gao, Fayi Cui, and Xijun Wu

Doc ID: 326774 Received 23 Mar 2018; Accepted 04 Jun 2018; Posted 07 Jun 2018  View: PDF

Abstract: Manipulation of photoluminescence (PL) of monolayer(ML) molybdenum disulfide (MoS2) with metallic plasmonic nanostructures has attracted much more attention for their potential applications in optoelectronic devices. However, due to the limitation of resonance wavelength and oxidation properties, gold and silver are not the best selections for manipulating PL of MoS2. Here, we employ aluminum (Al) disks to tune the PL of ML MoS2. We have found that PL enhancement reaches the maximum when plasmonic resonances of Al disks overlap with the absorption peaks of ML MoS2. Near-field simulations show that PL enhancement is due to weak plasmon-exciton coupling.

Common-path surface plasmon interferometer with radial polarization

Bei Zhang, Chengqian Zhang, Michael Somekh, peng yan, and L W

Doc ID: 327981 Received 09 Apr 2018; Accepted 04 Jun 2018; Posted 11 Jun 2018  View: PDF

Abstract: We present a common-path surface plasmon interferometer with radial polarization. We show how the V(z) effect, the output of the microscope versus defocus z, can be derived utilizing a radially polarized illumination and a virtual annulus. The measurement of V(z) effect gives strong signature of the surface plasmon propagation which is functional related with the material properties. We discuss the advantages of using radial polarization compared to linear polarization.

Enhancement of strain measurable range and spatial resolution of OFDR based on local similar characters of Rayleigh scattering spectrum

Kunpeng Feng, Jiwen Cui, Dong Jiang, hong dang, Yihua JIn, Xun Sun, Yizhao Niu, and Jiubin Tan

Doc ID: 325445 Received 09 Mar 2018; Accepted 04 Jun 2018; Posted 13 Jun 2018  View: PDF

Abstract: Local similar characteristics of Rayleigh scattering (RS) fingerprint spectrum are discovered and an improved OFDR based on local similarity of RS spectrum is thus proposed to ensure the feasibility of OFDR during measuring large distribution strain with a high spatial resolution. The length and location of local spectrum are optimized to obtain a high spectral similarity between the reference and measurement spectrum (ReS and MeS) and achieve a robust suppression on cross-correlation fake peak and multi-peaks. This method relies on matching local ReS on MeS rather than a direct cross-correlation between whole ReS and MeS in conventional OFDR methods. By this method, 4 times enhancement of similarity is experimentally achieved comparing to conventional OFDR methods when the measured distribution strain varies from 0 to 3000 µε with a 3 mm long fiber gauge. Experimental results verify that it effectively avoids influences of fake peak and multi-peaks. Advantages of this method are large strain measurable range, robust performance, high SNR, and applicability with current OFDR systems.

Broadband high-order mode of spoof surface plasmon polaritons supported by compact complementary structure with high efficiency

Dawei Zhang, Kuang Zhang, Ruiwei Dai, Qun Wu, and xuejun sha

Doc ID: 328744 Received 18 Apr 2018; Accepted 04 Jun 2018; Posted 07 Jun 2018  View: PDF

Abstract: In this work, spoof surface plasmon polaritons (SSPPs) supported by microstrip lines with T-shaped complementary grooves are proposed. Compared with the traditional SSPP structure based on single-conductor transmission lines, broadband high-order mode of SSPPs can be predicted from the dispersion diagrams. Besides, a decrease in transverse size of 75% can be realized under the same asymptotic frequency. Then a smooth and simple transition which is composed of gradient complementary grooves is designed to realize high-efficiency excitation and support practical applications of high-order mode of SSPPs. As a result, seamless connection with microstrip lines is easily achieved without using flaring ground which simplifies the design procedure. Based on the proposed structure, a prototype of SSPP waveguide is designed and fabricated. Both numerical and experimental results validate efficient excitation and broadband propagation (up to 12 GHz) of high-order mode of SSPPs. This work will greatly accelerate the development of advanced plasmonic integrate circuits at microwave frequencies.

10 W-level gain-switched all-fiber laser at 2.8 µm

Pascal Paradis, Vincent Fortin, Yigit Aydin, Real Vallee, and Martin Bernier

Doc ID: 330672 Received 30 Apr 2018; Accepted 04 Jun 2018; Posted 07 Jun 2018  View: PDF

Abstract: We report a simple-design gain-switched all-fiber laser emitting a maximum average output power of 11.2 W at 2.826 µm. The corresponding extracted pulse energy is 80 µJ at a pulse duration of 170 ns. These performances significantly surpass previous gain-switched demonstrations and are close to the state of the art Q-switched laser performances near 2.8 µm, but with a much simpler and robust all-fiber design. The splice-less laser cavity is made of a heavily erbium-doped fluoride glass fiber and is bounded by fiber Bragg gratings written directly in the gain fiber through the protective polymer coating.

Three-dimensionally structured voxels for volumetric display

Kota Kumagai, Ibuki Yamaguchi, and Yoshio Hayasaki

Doc ID: 326675 Received 23 Mar 2018; Accepted 04 Jun 2018; Posted 14 Jun 2018  View: PDF

Abstract: A three-dimensional volumetric display has been the goal of the display research field for many years. However, volumetric displays capable of rendering multi-color and real-time graphics that users can view with the naked eye are still a challenge. Here, we show a new volumetric display using three-dimensionally structured fluorescent voxels. The fluorescent voxels were generated by two-photon excitation with a femtosecond laser. In order to realize colorization, volumetric graphics were spatially rendered on a multilayer fluorescent screen in which structured voxels having different luminescent colors were arranged in each layer. The color of the fluorescent voxels was changed by a holographic color switching method using computer-generated holograms displayed on a liquid-crystal spatial light modulator. Since this display employed RGB fluorescent voxels that are accessed optically, it has a number of advantages, such as being observable with the naked eye, and being capable of multi-color rendering and refreshable graphics. This technology will open up a wide range of applications in three-dimensional displays, augmented reality and computer graphics.

A facile way to obtain the defect modes in photonic crystal heterostructure

Liming Zhao, Yun-Song Zhou, and Ai-Hua Wang

Doc ID: 332180 Received 21 May 2018; Accepted 03 Jun 2018; Posted 07 Jun 2018  View: PDF

Abstract: A very facile way to obtain the defect modes in one-dimensional photonic crystalheterostructure are proposed in this paper. It is foundthat the defect modes can be generated by introducing theinterfaces, and the number of defect modes equals the number ofintroduced interfaces. All of these defect modes originating fromthe different geometric Zak phase can creat two band branches whichare governed by the two different interfaces. We further find thatthe two band branches can be renormalized into one band branch withdiscrete energy levels in the form of sinusoidal function.We believe that these findings can be used to provide direct guidance for practical application, and can also make the estimation of practical samples more convenient.

Multi-axis heterodyne vibrometer for simultaneous observation of 5 degrees of dynamic freedom from a single beam

James Perea, Brad Libbey, and George Nehmetallah

Doc ID: 331032 Received 04 May 2018; Accepted 02 Jun 2018; Posted 04 Jun 2018  View: PDF

Abstract: A multi-axis heterodyne interferometer concept is under development for observations of five degrees of dynamic freedom using a single illumination source. This paper presents a laboratory system that combines elements of heterodyne Doppler vibrometry, holography, and digital image correlation to simultaneously quantify in-plane translation, out-of-plane rotation, and out-of-plane displacement. The sensor concept observes a dynamic object by mixing a single optical field with heterodyne reference beams and collecting these combined fields at the image and Fourier planes, simultaneously. Polarization and frequency multiplexing are applied to separate two segments of a receive Mach-Zehnder interferometer. Different optical configurations are utilized; one segment produces a focused image of the optical field scattered off the object while the other segment produces an optical Fourier transform of the optical field scattered off the object. Utilizing the amplitude and phase from each plane allows quantification of multiple components of transient motion using a single, orthogonal beam.

Resonance in modulation instability from non-instantaneous nonlinearities

Ray-Kuang Lee, Ray-Ching Hong, Chun-Yan Lin, You-Lin Chuang, Chien-Ming Wu, You-Nan Su, Jeng Yi Lee, Chien-Chung Jeng, and Ming-Feng Shih

Doc ID: 330891 Received 03 May 2018; Accepted 02 Jun 2018; Posted 13 Jun 2018  View: PDF

Abstract: To explore resonance phenomena in the nonlinear region, we show by experimental measurements and theoretical analyses that resonance happens in modulation instability (MI) from non-instantaneous nonlinearities in photorefractive crystals. With a temporally periodic modulation in the external bias voltage, corresponding to a modulation in the nonlinear strength, an enhancement in the visibility of MI at resonant frequency is reported through spontaneous optical pattern formations.Theoretical curves obtained from a nonlinear non-instantaneous Schr\"{o}dinger equation give good agreement to experimental data.

High-extinction-ratio directional-coupler-type polarization beam splitter with a bridged silicon wire waveguide

Yoohna Kim, Moon Hyeok Lee, YUDEUK Kim, and Kyong Hon Kim

Doc ID: 330908 Received 04 May 2018; Accepted 31 May 2018; Posted 11 Jun 2018  View: PDF

Abstract: We demonstrate an integrated polarization beam splitter (PBS) of a simple and compact device geometry with high polarization extinction ratios (PERs). A silicon PBS based on a three waveguide directional coupler is numerically simulated for optimum device parameters, and fabricated experimentally. The measured PER values of the fabricated PBSs are 40.74 dB, and 39.01 dB for TE and TM modes, respectively, and their corresponding insertion losses (ILs) are 0.35 dB on average for a coupler length of about 29.4 μm.

Writing and Erasing of Temporal Kerr Cavity Solitons via Intensity Modulation of the Cavity Driving Field

Yadong Wang, Bruno Garbin, François Leo, Stephane Coen, Miro Erkintalo, and Stuart Murdoch

Doc ID: 328107 Received 10 Apr 2018; Accepted 31 May 2018; Posted 04 Jun 2018  View: PDF

Abstract: We experimentally and numerically study the use of intensity modulation for the controlled addressing of temporal Kerr cavity solitons. Using a coherently driven fiber ring resonator, we demonstrate that a single temporally broad intensity modulation pulse applied on the cavity driving field permits systematic and efficient writing and erasing of ultrashort cavity solitons. We use numerical simulations based on the mean-field Lugiato-Lefever model to investigate the addressing dynamics, and present a simple physical description of the underlying physics.

Single-shot real-time detection technique for pulse-front tilt and curvature of femtosecond pulsed beams with multiple-slit spatiotemporal interferometry

Zhaoyang Li, Noriaki Miyanaga, and Junji Kawanaka

Doc ID: 330417 Received 26 Apr 2018; Accepted 31 May 2018; Posted 31 May 2018  View: PDF

Abstract: Spatiotemporal distortions of femtosecond pulsed beams could significantly reduce the focal-spot intensity of intense lasers. We theoretically present a very simple method for single-shot real-time detecting pulse-front tilt, curvature or tilt and curvature (PFT, PFC or PFT&PFC) by using multiple-slit spatiotemporal interferometry. An unknown pulsed beam is spatially cut by a high-density multiple-slit and changed into a series of spatially separated sub-pulses. By measuring the spatial distribution of the interference pattern, PFT, PFC or PFT&PFC can be qualitatively detected. Comparing with recent methods, no reference pulses, no temporal or spatial scanning and no temporal or spectral measurement is required. The single-shot and spatial-only detection will greatly simplify the real-time detection of spatiotemporal distortions.

Less than 1% quantum defect fiber lasers via Yb-doped multicomponent fluorosilicate optical fiber

Nanjie Yu, Maxime Cavillon, Courtney Kucera, Thomas Hawkins, John Ballato, and Peter Dragic

Doc ID: 330484 Received 27 Apr 2018; Accepted 31 May 2018; Posted 31 May 2018  View: PDF

Abstract: Two ytterbium-doped fiber lasers exhibiting quantum defects of less than 1% are demonstrated, in which pumping at wavelengths of 976.6 nm and 981.0 nm yielded lasing at wavelengths of 985.7 nm and 989.8 nm, respectively. The multicomponent fluorosilicate active optical fiber, fabricated using the molten core method, has spectral characteristics similar to those of fluoride glasses, namely short average emission wavelength and long upper state lifetime. A best-case slope efficiency of 62.1% was obtained, matching very well the theoretical model. With further fiber and laser optimization, slope efficiencies approaching the quantum limit should ultimately be possible. A reduction in the quantum defect may offer significant mitigation of issues associated with fiber heating. As such, this work can serve as a possible direction for future scaling of high-power fiber laser systems.

Multi-wavelength add-drop filter with phase-modulatedshifted Bragg grating

Somnath Paul, Markku Kuittinen, Matthieu Roussey, and Seppo Honkanen

Doc ID: 330872 Received 02 May 2018; Accepted 31 May 2018; Posted 07 Jun 2018  View: PDF

Abstract: We present, for the first time, a multichannel add-dropoperation with a phase modulated shifted Bragg grat-ing based filter. The device is realized in silicon-on-insulator waveguide platform with TiO2 as a coatingmaterial to reduce the refractive index contrast. Theoperation is shown for three and five wavelength chan-nels within the telecom C-band. A line width of0.6 nm with an extinction ratio of 20 dB is achieved.The shifted Bragg grating is modulated maintaininga modal phase matching condition for multiple wave-lengths. The phase function is calculated with an itera-tive Fourier transform algorithm. The experimental re-sults are in very good agreement with the design.

High-detectivity optical heterodyne method for wideband carrier-envelope phase noise analysis of laser oscillators

Haochen Tian, Nils Raabe, Youjian Song, Gunter Steinmeyer, and Ming-lie Hu

Doc ID: 315552 Received 29 May 2018; Accepted 30 May 2018; Posted 01 Jun 2018  View: PDF

Abstract: Broadband characterization of the carrier-envelope phase (CEP) noise spectral density of free-running mode-locked lasers is essential for advanced low-noise optical frequency comb (OFC) designs. Here we present a direct method that utilizes an optical heterodyne between a pair of repetition-rate-locked mode-locked lasers for CEP noise characterization, without requiring an f-2f interferometer or nonlinear optical conversion steps. A proof-of-principle experiment in a free-running femtosecond Yb-fiber laser achieves CEP noise spectral density characterization with >270 dB dynamic range over a Fourier frequency range from 5 mHz to 8 MHz. The measurement noise floor is well below 1 μrad/√Hz, enabling dependable detection down to a quantum-limited noise floor. The method can resolve various noise mechanisms that cause specific CEP noise spectral shapes. The underlying mechanisms are further analyzed in terms of spurious temporal correlation as to distinguish between technical and stochastic noise signatures. Moreover, a Hadamard deviation analysis reveals a varying degree of frequency stability in the measured CEP time series.

High-quality Tailored-Edge Cleaving Using Aberration-corrected Bessel-like Beams

Michael Jenne, Daniel Flamm, Taoufiq Ouaj, Julian Hellstern, Jonas Kleiner, Daniel Großmann, Maximilian Koschig, Myriam Kaiser, Malte Kumkar, and Stefan Nolte

Doc ID: 327637 Received 05 Apr 2018; Accepted 30 May 2018; Posted 30 May 2018  View: PDF

Abstract: We report on the usage of ultrashort laser pulses in form of aberration-corrected Bessel-like beams for laser cutting of glass with bevels. Our approach foresees to incline the material's entrance surface with respect to the processing optics. The detailed analysis of phase distortions caused by the beam transition through the tilted glass surface allows to pre-compensate occurring aberrations using digital holography. We verify theoretical considerations by means of pump-probe microscopy and present high-quality edges in non-strengthened silicate glass.

Design of optical systems with toroidal curved detectors

Eduard Muslimov, Emmanuel Hugot, Marc FERRARI, Thibault Behaghel, Gerard LEMAITRE, Melanie Roulet, and Simona Lombardo

Doc ID: 327818 Received 06 Apr 2018; Accepted 30 May 2018; Posted 31 May 2018  View: PDF

Abstract: We consider using toroidal curved detectors to improve the performance of imaging optical systems. We demonstrate that some optical systems have an anamorphic field curvature. We consider an unobscured re-imaging three-mirror anastigmat as an example (f’=960 mm, F/5.3, ωx x ωy=4°x4°). By assuming that the image is focused on a toroidal detector surface and perform re-optimization, it becomes possible to obtain a notable gain in the image quality - up to 40% in terms of the spot RMS radius.. Through analytic computations and finite-element analysis, we demonstrate that this toroidal shape can be obtained by bending of a thinned detector in a relatively simple setup.

Ionization-assisted spatio-temporal localization in gas-filled capillaries

Xiaohui Gao, Gauri Patwardhan, Bonggu Shim, Tenio Popmintchev, Margaret Murnane, Henry Kapteyn, and Alexander Gaeta

Doc ID: 328140 Received 18 Apr 2018; Accepted 30 May 2018; Posted 31 May 2018  View: PDF

Abstract: We demonstrate numerically and experimentally that intense pulses propagating in gas-filled capillaries can undergo localization in space and time due to strong plasma defocusing. This phenomenon can occur below or above the self-focusing threshold $P_{cr}$ as a result of ionization-induced refraction that excites higher-order modes. The constructive interference of higher-order modes leads to spatio-temporal localization and resurgence of the intensity. Simulations show that this confinement is more prominent at shorter wavelength pulses and for smaller capillary diameters. Experiments with ultraviolet pulses confirm that this ionization-induced refocusing appears below $P_{cr}$ and thus represents a mechanism for spatio-temporal confinement without self-focusing.

Experimental Implementation of Generalized Transitionless Quantum Driving

Chang-Kang Hu, Jin-Ming Cui, Alan Santos, YunFeng Huang, Marcelo Sarandy, Chuanfeng Li, and Guang-can Guo

Doc ID: 330948 Received 07 May 2018; Accepted 29 May 2018; Posted 30 May 2018  View: PDF

Abstract: It is known that high intensity fields are usually required to implement shortcuts to adiabaticity via Transitionless Quantum Driving (TQD). Here, we show that this requirement can be relaxed by exploiting the gauge freedom of generalized TQD, which is expressed in terms of an arbitrary phase when mimicking the adiabatic evolution. We experimentally investigate the performance of generalized TQD in comparison with both traditionalTQDand adiabatic dynamics. By using a 171Yb+ trapped ion hyperfine qubit, we implement a Landau-Zener adiabatic Hamiltonian and its (traditional and generalized) TQD counterparts. We show that the generalized theory provides optimally implementable Hamiltonians for TQD, with no additional fields required. In addition, the optimal TQD Hamiltonian for the Landau-Zener model is investigated under dephasing. Even using less intense fields, optimalTQD exhibits fidelities that are more robust against a decohering environment, with performance superior than that provided by the adiabatic dynamics.

Tailoring polarization singularities in a Gaussian beam with locally linear polarization

Alexey Kovalev and Victor Kotlyar

Doc ID: 325307 Received 02 Mar 2018; Accepted 29 May 2018; Posted 30 May 2018  View: PDF

Abstract: Here, we theoretically study Gaussian beams with arbitrarily located polarization singularities (PS). Under PS we mean here an isolated intensity null with radial, azimuthal, or radial-azimuthal polarization around it. An expression is obtained for the complex amplitude of such beams. We study in details a case when the PSs are located in the vertices of a regular polygon. If such a beam has one or two PSs, these PSs are centers of radial polarization. If there are three PSs, then one of them has radial polarization and the other two have mixed radial-azimuthal polarization. If the beam has four PSs, then there are two PSs with radial polarization and two PSs with azimuthal polarization. When propagating in space, PSs are shown to appear in a discrete set of planes, in contrast to the phase singularities existing in any plane. If the beam has two PSs, their polarization is shown to transform from the radial in the initial plane to the azimuthal in the far field. The results can find application in optical communications by using non-uniform polarization.

Launching phase-controlled surface plasmons on Babinet metasurfaces

Lijun Guo, Bin Zheng, Kun Zheng, Muhiddeen Yahaya, Shang Gao, Zehao Wang, Shahram Dehdashti, Hongsheng Chen, and Yihao Yang

Doc ID: 330187 Received 24 Apr 2018; Accepted 29 May 2018; Posted 11 Jun 2018  View: PDF

Abstract: Surface plasmons are electromagnetic modes bounded at the metal-dielectric interfaces, which have numerous applications, due to the strong field enhancement effect. Therefore, controlling surface plasmons is highly demanded for the modern photonics and plasmonics. In this work, we propose a kind of metasurface for launching surface plasmons with controlled phase based on Babinet principle. The phase control are achieved by arranging C-shaped apertures on a metal surface which exhibit high-efficient electric dipole resonance. By properly designing the spatial separation and orientation of the aperture resonators, arbitrary phase profile is achieved that allows anomalous (directional and focusing/diverging) surface plasmons launching and manipulation of the wavefront.

Tomographic phosphorescence lifetime multiplexing

Anand Kumar and Steven Hou

Doc ID: 326565 Received 10 Apr 2018; Accepted 28 May 2018; Posted 30 May 2018  View: PDF

Abstract: We present a tomographic reconstruction algorithm for recovering distributions of multiple phosphorescent dyes within turbid media from time-resolved measurements, using either point or spatially patterned sources and detectors. The algorithm employs a multi-exponential analysis of time-resolved data, followed by tomographic inversion of the decay amplitudes to recover independent yield distributions for each lifetime present in the medium. Using Monte Carlo simulations, we computationally demonstrate that this two-step inversion approach provides several-fold improvement in quantitative and localization accuracy compared to a direct inversion of the time domain phosphorescence. We also demonstrate the tomographic reconstruction of up to three phosphorescent lifetimes embedded in thick tissue. The proposed algorithm can allow quantitative multiplexed tomography of luminescent and phosphorescent dyes for a wide range of in vivo applications.

Generating and synthesizing ultra-broadband twisted light using compact silicon chip

Nan Zhou, Shuang Zheng, Xiaoping Cao, Shengqian Gao, shimao li, mingbo he, Xinlun Cai, and Jian Wang

Doc ID: 330331 Received 26 Apr 2018; Accepted 28 May 2018; Posted 01 Jun 2018  View: PDF

Abstract: Compact and broadband manipulation of spatial modes is of great importance in lots of emerging applications exploiting the space domain of lightwaves. Here, we report chip-scale generation and synthesization of ultra-broadband orbital angular momentum (OAM) modes (twisted light) on silicon platform. By simply introducing a sub-wavelength holographic fork grating on top of a silicon waveguide, the in-plane guided mode is converted to the free-space OAM mode. Inputs from both sides of the waveguide enable the synthesization of OAM modes. We design, simulate, fabricate and demonstrate the silicon-based ultra-broadband OAM generator/synthesizer. The generated OAM+1, OAM+2, OAM+3 and synthesized OAM+1 and OAM-1 show maximum purity of 0.93, 0.9, 0.87 and 0.9 and wide bandwidth (purity>0.85) of 384, 170, 145 and 41 nm. OAM+1, OAM+2 and OAM+3 show >0.75 purity over an ultra-broadband wavelength range from 1300 to 1700 nm. Reconfigurable chip-scale OAM synthesizer is also demonstrated in the experiment. The demonstrated chip-scale ultra-broadband OAM generator/synthesizer may find potential applications in multi-dimensional optical communication systems incorporating OAM and wavelength-division multiplexing (WDM) as well as OAM-based quantum key distribution (QKD) systems. © 2018 Optical Society of America

High-Speed Indoor Optical Wireless Communication System Employing a Silicon Integrated Photonic Circuit

KE WANG, Ampalavanapilla Nirmalathas, Christina Lim, Elaine Wong, Kamal Alameh, Hongtao Li, and Efstratios Skafidas

Doc ID: 328967 Received 20 Apr 2018; Accepted 27 May 2018; Posted 31 May 2018  View: PDF

Abstract: Beam-steering-based optical wireless technologies are being widely investigated due to the capability of providing high-speed wireless connectivity in indoor applications. However, high-speed indoor optical wireless systems are traditionally realized with discrete bulky components, significantly limiting their practical applications. In this paper, we demonstrate the principle of an infrared optical wireless communication system employing a miniaturized silicon integrated photonic circuit for beam steering. Experimental results show that up to 12.5 Gb/s optical wireless communication can be achieved with error-free performance over a free-space range of 140 cm, and limited mobility of users can be realized. The experimental results of this paper open the way for realizing compact high-speed optical wireless communications.

Subwavelength engineering and asymmetry: two efficient tools for sub-nanometer-wide silicon Bragg filters

Dorian Oser, Diego Pérez-Galacho, Carlos Alonso-Ramos, Xavier Le Roux, Sebastien Tanzilli, Laurent Vivien, laurent labonte, and Eric Cassan

Doc ID: 326550 Received 22 Mar 2018; Accepted 26 May 2018; Posted 31 May 2018  View: PDF

Abstract: Bragg filters stand as a key building blocks of the silicon-on-insulator (SOI) photonics platform, allowing the implementation of advanced on-chip signal manipulation. However, achieving narrowband Bragg filters with large rejection levels is often hindered by fabrication constraints and imperfections. Here, we show that the combination of single-side corrugation asymmetry and subwavelength engineering opens a new path for the realization of high performance Bragg filters, overcoming minimum feature size constraints. We comprehensively study the impact of the corrugation asymmetry in conventional and subwavelength single-etched SOI Bragg filters, showing their potential for bandwidth reduction. Finally, we experimentally demonstrate a novel subwavelength geometry, based on shifted corrugation teeth, achieving null-to-null bandwidths and rejections of 0.8 nm and 40 dB for the symmetric configuration, and 0.6 nm and 15 dB for the asymmetric case.

Simultaneous Wideband Radio-Frequency Self-Interference Cancellation and Frequency Downconversion for In-Band Full-Duplex ROF Systems

Yang Chen and Shilong Pan

Doc ID: 327641 Received 17 Apr 2018; Accepted 26 May 2018; Posted 01 Jun 2018  View: PDF

Abstract: A photonic approach for simultaneous wideband radio-frequency (RF) self-interference cancellation and frequency downconversion in in-band full-duplex radio-over-fiber system is proposed based on a dual-polarization quadrature phase shift-keying (DP-QPSK) modulator. The upper DP-MZM in the DP-QPSK modulator is used to cancel the self-interference directly in the optical domain and generate two sidebands of the desired RF signal, whereas the lower DP-MZM generates two sidebands of the local oscillator. After detecting the combined optical signal at a photodetector, the desired RF signal is downconverted to an intermediate frequency (IF) signal with the self-interference cancelled. The proposed approach can overcome the reappearance of the interference signal and the power fading effect of the received signal caused by fiber dispersion. An experiment is performed. The cancellation depth for single frequency interference cancellation is around 58 dB, whereas that for the wideband interference cancellation is larger than 25 dB. The fading effect of the proposed IF transmission system is also evaluated compared with the traditional RF transmission system.

Evolution of nonlinear Raman-Nath diffraction from near field to far field

Dongmei Liu, Dunzhao Wei, Min Gu, Yong Zhang, Xiaopeng Hu, Min Xiao, and peng Han

Doc ID: 331030 Received 07 May 2018; Accepted 26 May 2018; Posted 07 Jun 2018  View: PDF

Abstract: We studied the near-field effect of nonlinear Raman–Nath diffraction experimentally in a one-dimensional periodically poled LiTaO3 crystal and established the theoretical relationship between the nonlinear effect in the near field and the corresponding effect in the far field. The interference of far-field spots in the near field constitutes the nonlinear Talbot self-imaging effect. Our results not only enhance our understanding of the nonlinear Talbot effect but also indicate potential applications of this effect in domain inspection and domain design.

Fast Photorefractive Response in Polymeric Composites Enabled by the Control of Chromophore Free Volume

Jongwan Choi, Jong-Sik Moon, Felix Kim, and Jin-Woo Oh

Doc ID: 324961 Received 12 Mar 2018; Accepted 26 May 2018; Posted 14 Jun 2018  View: PDF

Abstract: The molecular orientation of a chromophore importantly affects the electro-optic characteristics of polymeric photorefractive composites. We designed methyl, ethyl, and isopropyl derivatives of 4-piperidinobenzylidene-malononitrile (PDCST) with the aim of enhancing molecular orientation properties, and investigated the effects of alkyl substitution on the electro-optic properties and response times of polymeric photorefractive composites. The three alkyl-substituted PDCSTs showed enhanced electro-optic responses and photorefractive grating build-up rates.

1.34 μm VECSEL mode-locked with a GaSb-based SESAM

Antti Harkonen, Soile Suomalainen, Antti Rantamäki, Jari Nikkinen, Yicheng Wang, Uwe Griebner, Gunter Steinmeyer, and Mircea Guina

Doc ID: 328686 Received 18 Apr 2018; Accepted 26 May 2018; Posted 19 Jun 2018  View: PDF

Abstract: Mode-locking of a 1.34 µm vertical external cavity surface emitting laser (VECSEL) is demonstrated using a GaSb-based semiconductor saturable absorber mirror (SESAM). The SESAM includes six AlGaSb quantum wells with an absorption edge at ~1.37 μm. The proposed approach has two key benefits: the quantum wells can be grown lattice matched, and only a small number of Bragg reflector layers is required to provide high reflectivity. Pump–probe measurements also reveal that the AlGaSb/GaSb structure exhibits an intrinsically fast absorption recovery on a picosecond time scale. The mode-locked laser pulse train had a fundamental repetition rate of 1.03 GHz, a pulse duration of ~5 ps, and a peak power of ~1.67 W. The demonstration paves the way for exploiting GaSb-based SESAMs for mode-locking in the 1.3–2 μm wavelength range, not sufficiently addressed by GaAs and InP material systems.

Retrieval of weak x-ray scattering using edge illumination

Charlotte Maughan Jones, Fabio Vittoria, A Olivo, Marco Endrizzi, and Peter Munro

Doc ID: 327895 Received 10 Apr 2018; Accepted 24 May 2018; Posted 05 Jun 2018  View: PDF

Abstract: X-ray phase contrast imaging (XPCi) provides additional modes of image contrast compared to conventional absorption based x-ray imaging, thus providing additional structural and functional information about the sample. The edge illumination (EI) technique has been used to provide absorption, refraction and scattering contrast in both biological and non-biological samples, however the retrieval of low scattering signals remains problematic, principally due to beam hardening by the sample. We present a new retrieval method which successfully overcomes the limitations caused by beam hardening, and provide examples of the retrieval of such signals in highly absorbing, weakly scattering samples.

Electrospun polymer bottle microresonators for stretchable single-mode lasing devices

SAIMA UBAID, Feng Liao, Shuangyi Linghu, Jiaxin Yu, and Fuxing Gu

Doc ID: 328173 Received 12 Apr 2018; Accepted 24 May 2018; Posted 31 May 2018  View: PDF

Abstract: We report a simple electrospinning method to fabricate polymer bottle microresonators, which are doped with a lasing gain material and supported by electrospun polymer micro/nanofibers on a flexible grooved polymer substrate. The fabricated bottle microresonators have smooth outer surface and high quality. By using an interference light pump approach, single whispering gallery mode lasing is obtained, with a side-mode suppression factor over 20 dB. By mechanically stretching the grooved substrate, tunability of the lasing peaks is demonstrated. Our method has advantages of time saving and low cost, and may have promising applications in stretchable lasing and sensing devices.

Continuous surface single-focus spiral zone plates

Zhen-Nan Tian, Qi-Dai Chen, Zhi-Yong Hu, Yi-Ke Sun, Yan-Hao Yu, Hong Xia, and Hong-Bo Sun

Doc ID: 330102 Received 30 Apr 2018; Accepted 23 May 2018; Posted 31 May 2018  View: PDF

Abstract: In this letter, we report continuous surface spiral zone plates (C-SZPs) fabricated by femtosecond laser direct writing. The novel optical element can generate a single-focus vortex beam owing to the element’s complicated continuous surface. The C-SZP surface possesses reverse mirror-rotation symmetry, which ensures that the transfer element has the same surface morphology as the original element. Both the transfer element and original element have good optical properties. The single-focus behavior was investigated by a microscopic imaging system and found to be in good agreement with theoretical simulation results. The innovative optical component is expected to be widely used in optical communication, quantum computation, optical manipulation, and other fields.

Imaging through extreme scattering in extended dynamic media

Andrey Kanaev, Abbie Watnik, Dennis Gardner, chris metzler, Kyle Judd, Paul Lebow, Kyle Novak, and james lindle

Doc ID: 318130 Received 05 Jan 2018; Accepted 18 May 2018; Posted 30 May 2018  View: PDF

Abstract: Critical to navigation, situational awareness, and object identification is the ability to image through turbid water and fog. To date, the longest imaging ranges in such environments rely on active illumination and selection of ballistic photons by means of time gating. Here we show that the imaging range can be extended by using time-gated holography in combination with multi-frame processing. Instead of simply summing the intensity of the frames, we use the complex fields retrieved through digital holographic processing and coherently add the frames. We demonstrate imaging through extended bodies of turbid water and fog at one-way attenuation lengths of 13 and 13.6, respectively. Compared to equivalent traditional time-gated systems, gated-holography and coherent processing require 20X less laser illumination power for the same imaging range.

Nonlinearity Mitigation of Intensity Modulation and Coherent Detection Systems

Jinlong Wei, Nebojsa Stojanovic, and Changsong Xie

Doc ID: 326137 Received 19 Mar 2018; Accepted 18 May 2018; Posted 31 May 2018  View: PDF

Abstract: Coherent optical communication systems are still too expensive solutions for metro and short reach networks in the near future. Coherent detection with intensity modulator replacing costly dual-polarization I/Q modulator could offer a good trade-off between cost and performance for metro networks. The major performance limit of such systems is the nonlinearity. To our best knowledge, this paper offers the first known investigation on nonlinearity of a high speed intensity modulation and coherent detection system using an integrated laser and electro-absorption modulator. Advanced nonlinearity mitigation digital signal processing (DSP) are proposed including a 2 × 1 multiple-input single-output complex transversal Volterra FFE filter, a first proposed post-FFE noise cancellation filter taking into account both pre- and post-cursor noise correlations based on a simple autocorrelation coefficient calculation, and a maximum likelihood sequence estimator. The receiver DSP needs no carrier and phase recovery thus is much simpler than a conventional coherent receiver DSP. Results show that, compared to a simple linear FFE equalization, the proposed nonlinear DSP enables over 8-dB and 4-dB improvement in OSNR sensitivity at 7% overhead hard-decision feedforward error correction (FEC) and 20% overhead soft-decision FEC threshold BERs, respectively, for a 56-Gb/s intensity modulation and coherent detection system. A record 18-dB OSNR sensitivity at hard-decision FEC threshold BER of 3.8E-3 is also achieved.

FLUORESCENCE TIME-RESOLVED MACROIMAGING

Vladislav Shcheslavskiy, Marina Shirmanova, Varvara Dudenkova, Konstantin Lukyanov, Alena Gavrina, Anastasia Shumilova, Elena Zagaynova, and Wolfgang Becker

Doc ID: 327900 Received 13 Apr 2018; Accepted 08 May 2018; Posted 14 May 2018  View: PDF

Abstract: While laser scanning fluorescence lifetime imaging (FLIM) is a powerful approach for cell biology, its small field of view (typically less than 1 mm) makes it impractical for imaging of large biological samples that is often required for biomedical applications. Here we present a system that allows to perform FLIM on macroscopic samples as large as 18mm with a lateral resolution of 15μm. The performance of the system is verified with FLIM of endogenous metabolic cofactor reduced nicotinamide adenine dinucleotide (phosphate), NAD(P)H, and genetically encoded fluorescent protein mKate2 in a mouse tumor in vivo.

Optical trapping with planar silicon metalenses

Georgiy Tkachenko, Daan Stellinga, Andrei Ruskuc, Mingzhou Chen, Kishan Dholakia, and Thomas Krauss

Doc ID: 326126 Received 15 Mar 2018; Accepted 02 May 2018; Posted 03 May 2018  View: PDF

Abstract: Contactless manipulation of micron-scale objects in a microfluidic environment is a key ingredient for a range of applications in the biosciences, including sorting, guiding and analysis of cells and bacteria. Optical forces are powerful for this purpose but typically require bulky focusing elements to achieve the appropriate optical field gradients. To this end, realizing the focusing optics in a planar format would be very attractive and conducive to integration of such microscale devices either individually or as arrays. Here, we report on the first experimental demonstration of optical trapping in water using planar silicon metalenses illuminated with a collimated laser beam. The structuresconsist of high-contrast gratings with a locally varying period and duty-cycle. They are designed to mimic parabolic reflectors with a numerical aperture of 0.56 at a vacuum wavelength of 1064 nm. We achieve both twoand three-dimensional trapping, with the latter realised by omitting the central Fresnel zones. The study highlights the versatility of such lithographically defined metastructures for exerting optical forces without the need for traditional optical elements.

Measuring high-order optical orbital angular momentum with a hyperbolic gradually-changing-period pure-phase grating

Zhibing Liu, She Gao, Wenda Xiao, Jishun Yang, xincheng huang, Yuanhua Feng, Jianping Li, Weiping Liu, and Zhaohui Li

Doc ID: 327299 Received 03 Apr 2018; Accepted 26 Apr 2018; Posted 09 May 2018  View: PDF

Abstract: We present a method to measure the high-order orbital angular momentum (OAM) state of a light beam with a static hyperbolic gradually-changing-period pure-phase grating (HGCP-PPG). From the number and orientation of the fringes of the Hermite-Gaussian like diffraction intensity pattern, the OAM state of the incident Laguerre-Gaussian beam can be measured. Experimental detection of the OAM state up to ±100-order has been achieved. This method is high efficient and robust because the HGCP-PPG is adaptive to high-order OAM beam and tolerant of the misalignment of the incident OAM beam.

656 W Er-doped Yb-free large-core fiber laser

Huaiqin Lin, Yujun Feng, Yutong Feng, Pranabesh Barua, Jayanta Sahu, and Johan Nilsson

Doc ID: 324633 Received 21 Feb 2018; Accepted 16 Apr 2018; Posted 19 Apr 2018  View: PDF

Abstract: A continuous-wave erbium-doped ytterbium-free fiber laser generates a record-breaking pump-power-limited output power of 656 W at ~1601 nm when cladding pumped by 0.98-μm diode lasers. The slope efficiency was 35.6% with respect to launched pump power and the beam quality factor (M²) was ~10.5. This M²–value excludes a fraction ~25% of the power which emerged from the cladding, which we attribute in part to mode-coupling between the 146-μm core and 700-μm inner cladding. Whereas these parameters are adequate for in-band tandem-pumping of Tm-doped fiber lasers, we predict that an output power of over 1 kW is possible by pumping with state-of-the-art 0.98-μm diode lasers, even with a smaller core that allows for improved beam quality.

Inverse prism based on temporal discontinuity andspatial dispersion

Alireza Akbarzadeh, Nima Chamanara, and Christophe Caloz

Doc ID: 321063 Received 31 Jan 2018; Accepted 13 Apr 2018; Posted 19 Apr 2018  View: PDF

Abstract: We introduce the concept of the inverse prism asthe dual of the conventional prism and deducefrom this duality an implementation of it based ontemporal discontinuity and spatial dispersion providedby anisotropy. Moreover, we show that thisinverse prism exhibits the following three uniqueproperties: chromatic refraction birefringence,ordinary-monochromatic and extraordinary polychromatictemporal refraction, and linear to-Lissajous polarization transformation.

Fast demodulated white-light interferometry based fiber-optic Fabry-Perot cantilever microphone

Ke Chen, Zhihao Yu, Qingxu Yu, Min Guo, Zhihao Zhao, Chao Qu, Zhenfeng Gong, and Yang Yang

Doc ID: 322923 Received 09 Feb 2018; Accepted 07 Apr 2018; Posted 13 Jun 2018  View: PDF

Abstract: We demonstrate a high sensitive and stable fiber-optic Fabry-Perot cantilever microphone based on a fast demodulated white-light interferometry (WLI). The cavity length of the low-finesse Fabry-Perot interferometry (FPI) is absolutely measured by realizing high-speed demodulation method utilizing full spectrum, with advantages of both high resolution and large dynamic range. Acoustic test demonstrates high sensitivities and linear responsivities at frequencies below 2 kHz. The pressure responsivity and the noise-limited minimum detectable acoustic pressure level are measured to be 211.2 nm/Pa and 5 μPa/Hz1/2 at the frequency of 1 kHz. Furthermore, comparative experimental results show that the signal-to-noise ratio (SNR) is over ten times higher than a reference condenser microphone.

Optical-resonance-enhanced nonlinearities in aMoS₂-coated single-mode fiber

Haojie Zhang, Noel Healy, Antoine Runge, Chung Che Huang, Daniel William Hewak, and Anna Peacock

Doc ID: 321040 Received 01 Feb 2018; Accepted 27 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: Few-layer molybdenum disulfide (MoS₂) has an electronicband structure that is dependent on the numberof layers and is, therefore, a very promising material foran array of optoelectronic, photonic and lasing applications.In this work, we make use of a side-polished opticalfiber platform to gain access to the nonlinear opticalproperties of the MoS₂ material. We show that the nonlinearresponse can be significantly enhanced via resonantcoupling to the thin film material, allowing for theobservation of optical modulation and spectral broadeningin the telecoms band. This route to access thenonlinear properties of 2D materials promises to yieldnew insights into their photonic properties.

Comment on: Tailoring axial intensity of laser beams with a heart-shaped hole, by Wang~\emph{et al.}

Riccardo Borghi

Doc ID: 322779 Received 07 Feb 2018; Accepted 20 Mar 2018; Posted 11 Jun 2018  View: PDF

Abstract: Some comments about the recently published Optics Letters paper ``Tailoring axial intensity of laser beams with a heart-shaped hole,' by Wang~\emph{et al.},Opt. Lett. 42, 4921 (2017), are provided.

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