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Wavelength-tunable high-order Hermite-Gaussian modes and OAM-tunable vortex beam in dual-off-axis pumped Yb:CALGO laser

Yijie Shen, Yuan Meng, Xing Fu, and Mali Gong

Doc ID: 312834 Received 06 Nov 2017; Accepted 07 Dec 2017; Posted 07 Dec 2017  View: PDF

Abstract: A dual-off-axis pumping scheme is presented to generate wavelength-tunable high-order Hermite-Gaussian (HG) modes in Yb:CaGdAlO4 (Yb:CALGO) lasers. The mode and wavelength can be actively controlled by the off-axis displacements and pump power without any supplementary intracavity elements. The purities of the output HG modes are quantified by intensity distributions and the measured M2 values. The highest order reaches m = 15 for stable HGm,0 mode and wavelengthtunable width is about 10 nm. Moreover, through externally converting the HGm,0 modes, the vortex beams with a large OAM-tunable range form ±1 to ±15 is produced. This work is effective for largely scaling the spectral and OAM tunable ranges of vortex beams.

Femtosecond Alexandrite laser passively mode-locked by InP/InGaP quantum-dot saturable absorber

Shirin Ghanbari, Ksenia Fedorova, Andrey Krysa, Edik Rafailov, and Arkady Major

Doc ID: 313056 Received 08 Nov 2017; Accepted 07 Dec 2017; Posted 07 Dec 2017  View: PDF

Abstract: An Alexandrite laser passively mode-locked using an InP/InGaP quantum-dot semiconductor saturable absorber mirror (QD-SESAM) was demonstrated. The laser was pumped at 532 nm and generated 380 fs and 420 fs pulses at 775 nm with an average output power of 295 mW and 325 mW, respectively. To the best of our knowledge, this is the first report on a passively mode-locked femtosecond Alexandrite laser using a SESAM in general and a quantum-dot SESAM in particular.

Optically induced transparency in bosonic cascade lasers

Timothy Liew and Alexey Kavokin

Doc ID: 308220 Received 29 Sep 2017; Accepted 07 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: Bosonic cascade lasers are terahertz (THz) lasers based on stimulated radiative transitions between bosonic condensates of excitons or exciton-polaritons confined in a trap. We study the interaction of an incoming THz pulse resonant in frequency with the transitions between neighboring energy levels of the cascade. We show that at certain optical pump conditions the cascade becomes transparent to the incident pulse: it neither absorbs nor amplifies it, in the mean field approximation. The populations of intermediate levels of the bosonic cascade change as the THz pulse passes, nevertheless. In comparison, a fermionic cascade laser does not reveal any of these properties.

Cavity-birefringence-dependent h-shaped pulse generation in a thulium-holmium doped fiber laser

Junqing Zhao, Lei Li, Luming Zhao, Dingyuan Tang, and Deyuan SHEN

Doc ID: 313173 Received 09 Nov 2017; Accepted 07 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: We report on a type of 2 μm h-shaped pulse generation in a thulium-holmium doped fiber laser, for the first time to the best of our knowledge, and also first experimentally investigate its cavity birefringence and pump power dependences. The pulsed operation is achieved by using an asymmetric nonlinear optical loop mirror (NOLM). ~52.7 m dispersion-shifted fiber and ~3.8 m ultra-high numerical aperture fiber are incorporated into the NOLM to increase its nonlinear effect. The h-shaped pulse shows both polarization state (PS) and pump power dependences even when only fibers with randomly weak birefringence are employed. By further incorporating different lengths of high birefringence polarization-maintaining fiber (PMF), i.e introducing different amounts of linear cavity birefringence, consequently much larger pulse tuning ranges can be realized. Especially when the PMF is lengthened to ~2.3 m, through tuning the PS the achieved longest pulse duration (~318.14 ns) can almost cover the whole repetition period (~3 .96 ns), corresponding to a pulse duty circle of ~98.2%, the largest ever reported from a fiber laser to the best of our knowledge. We demonstrate the related characteristics in detail.

Single-shot Fourier ptychography based on diffractively beam splitting

Xiaoliang He, cheng liu, and Jianqiang Zhu

Doc ID: 310079 Received 26 Oct 2017; Accepted 05 Dec 2017; Posted 06 Dec 2017  View: PDF

Abstract: An optical setup and corresponding reconstruction method are proposed to realize single shot Fourier ptychography(FP). Multiple angle-varied object waves are generated by placing a dammann grating at a certain distance behind the object, and the generated image array of low resolution corresponding to different diffraction orders formed on the detector plane is recorded simultaneously in a single exposure. The amplitude as well as the phase information of the object can be properly reconstructed with standard FP algorithm from the recorded image array. This method eliminates the requirement for the angular scanning of standard FP, and the total acquisition time is dramatically reduced. The feasibility of this proposed method was demonstrated both numerically and experimentally. The proposed method can drastically improve the performance of standard FP technique and make it very suitable for applications, where high imaging speed is required

Comparison of optical feedback dynamics of InAs/GaAs quantum dot lasers emitting solely on ground or excited states

Lyu-Chih Lin, Chih-Ying Chen, Heming Huang, Dejan Arsenijević, Dieter Bimberg, Frederic Grillot, and Fan-Yi Lin

Doc ID: 312950 Received 09 Nov 2017; Accepted 05 Dec 2017; Posted 06 Dec 2017  View: PDF

Abstract: We experimentally compare the dynamics of InAs/GaAs quantum dot lasers under optical feedback emitting exclusively on ground (GS) or excited (ES) states. By varying the feedback parameters and put focus either on their short and long cavity regions, various periodic and chaotic oscillatory states are found. The GS laser is shown to be more resistant to feedback, benefiting from its strong relaxation oscillation damping. In contrast, the ES laser can easily be driven into complex dynamics. While the GS laser is of importance for the development of isolator-free transmitters, the ES laser is essential for applications taking advantages of chaos.

Filamentation-free self-compression of mid-infrared pulses in birefringent crystals with second-order cascading-enhanced self-focusing nonlinearity

Rosvaldas Suminas, Gintaras Tamosauskas, and Audrius Dubietis

Doc ID: 312485 Received 02 Nov 2017; Accepted 05 Dec 2017; Posted 07 Dec 2017  View: PDF

Abstract: We experimentally demonstrate virtually lossless, filamentation-free and energy-scalable more than three-fold self-compression of mid-infrared laser pulses at 2.1 μm in a birefringent medium (β-BBO crystal), which stems from favorable interplay between the second-order cascading-enhanced self-phase modulation and anomalous group velocity dispersion. By choosing an appropriate input beam diameter and intensity, the self-compression down to sub-30 fs pulse widths with GW peak power is achieved without the onset of beam filamentation and associated nonlinear losses due to the multiphoton absorption, yielding the energy throughput greater than 86%.

Multi-electrode tunable liquid crystal lenses with one lithography step

Jeroen Beeckman, Tzu-Hsuan Yang, Inge Nys, John George, Tsung-Hsien Lin, and Kristiaan Neyts

Doc ID: 309665 Received 20 Oct 2017; Accepted 04 Dec 2017; Posted 05 Dec 2017  View: PDF

Abstract: Electrically tunable lenses offer the possibility to control the focal distance by applying an electric field. Different liquid crystal tunable lenses have been demonstrated. In order to minimize lens aberrations, multi-electrode designs allow to fine-tune the applied voltages for every possible focal distance. In this article we provide a novel multi-electrode design in which only one lithography step is necessary, thereby offering a greatly simplified fabrication procedure compared to earlier proposed designs. The key factor is the use of a high-permittivity layer in combination with floating electrodes.

Relative sensitivity variation law in the field of fluorescence intensity ratio thermometry

Leipeng Li, Yuan Zhou, feng qin, Yangdong Zheng, Hua Zhao, and Zhiguo Zhang

Doc ID: 313060 Received 09 Nov 2017; Accepted 04 Dec 2017; Posted 06 Dec 2017  View: PDF

Abstract: We study the variation law of relative sensitivity in the field of fluorescence intensity ratio thermometry. It is theoretically demonstrated that there must be only one maximum value of relative sensitivity upon the case where there is a positive offset in fitting function. Moreover, the method to obtain this maximum is proposed. Experimental results, taking the 5D1/5D0 levels of Eu3+ as examples, are in excellent accordance with the conclusion. The mechanism behind is then investigated, and other populating processes imposed on the 5D1 level which exert negative outcome on thermal sensitivity are found to play a key role in determination of this unique variation law.

Ultrafast saturable absorption of MoS2 nanosheets under different pulse-width excitation conditions

Juna Zhang, Hao Ouyang, Xin Zheng, Jie You, Runze Chen, Tong Zhou, Yizhen Sui, Yu Liu, Xiang'ai Cheng, and Tian Jiang

Doc ID: 314406 Received 28 Nov 2017; Accepted 04 Dec 2017; Posted 08 Dec 2017  View: PDF

Abstract: The newly raised two-dimensional material MoS2 is regarded as an ideal candidate for saturated absorbers. Here, the open-aperture Z-scan method is used to study the saturation absorption (SA) response of monolayer and multilayer MoS2, considering laser irradiation with different pulse-width. Specifically, in cases of 10 ns and 10 ps laser pulses, the accumulative nonlinearity (e.g., free carrier absorption (FCA)) coupled with SA is found in both monolayer and multilayer MoS2. However, under a 65 fs pulse laser, the instantaneous nonlinearity (e.g., two photon absorption (TPA)) and the SA effect turn to play a significant role. Additionally, the saturation of both TPA and FCA is observed in MoS2. Importantly, the modulation depth of MoS2 shows different change trends by adjusting the laser pulse-width.

Equivalence principle and quantum mechanics: quantum simulation with entangled photons

Stefano Longhi

Doc ID: 312698 Received 03 Nov 2017; Accepted 04 Dec 2017; Posted 04 Dec 2017  View: PDF

Abstract: Einstein‘s equivalence principle states the complete physical equivalence of a gravitational field and corresponding inertial field in an accelerated reference frame. However, to what extent the equivalence principle remains valid in non-relativistic quantum mechanics is a controversial issue. To avoid violation of the equivalence principle, Bargmann‘s superselection rule forbids a coherent superposition of states with different masses. Here we suggest a quantum simulation of non-relativistic Schroedinger particle dynamics in non-inertial reference frames, which is based on propagation of polarization-entangled photon pairs in curved optical waveguides. Violation of the equivalence principle can be detected in a Hong-Ou-Mandel quantum interference measurement.

Quantum limits on the time-bandwidth product of an optical resonator

Mankei Tsang

Doc ID: 308617 Received 05 Oct 2017; Accepted 03 Dec 2017; Posted 04 Dec 2017  View: PDF

Abstract: A thought-provoking proposal by Tsakmakidis et al. [Science 356, 1260 (2017)] suggests that nonreciprocal optics can break a time-bandwidth limit to passive resonators. Here I quantize their resonator model and show that quantum mechanics does impose a limit, or else requires extra noise to be added in the same fashion as amplified spontaneous emission in active resonators. I also use thermodynamics to argue that extra dissipation or noise must be present in their proposed device.

Aberration-free calibration for 3D single molecule localization microscopy

Clément Cabriel, Nicolas Bourg, Guillaume Dupuis, and Sandrine Leveque-Fort

Doc ID: 309151 Received 13 Oct 2017; Accepted 03 Dec 2017; Posted 04 Dec 2017  View: PDF

Abstract: We propose a straightforward sample-based technique to calibrate the axial detection in 3D single molecule localization microscopy (SMLM). Using microspheres coated with fluorescent molecules, the calibration curves of PSF-shaping- or intensity-based measurements can be obtained for any required depth range from a few hundreds of nm to several tens of µm. This experimental method takes into account the effect of the spherical aberration without requiring computational correction.

Measurements of milli-Newton surface tension forces with tilted fiber Bragg gratings

Yu Shen, Chuan Zhong, Dejun Liu, Xiaokang Lian, Jianyao Zheng, Jing Jing Wang, Yuliya Semenova, Gerald Farrell, Jacques Albert, and John Donegan

Doc ID: 308747 Received 09 Oct 2017; Accepted 03 Dec 2017; Posted 07 Dec 2017  View: PDF

Abstract: Small lateral forces (lower than 0.1 N) cannot normally be measured with conventional single mode fiber-based sensors because of the high value of their Young modulus (>70 GPa). Here we demonstrate the measurement of lateral forces in the range from 0.2-1.4×10-3 N with a tilted fiber Bragg grating (TFBG) in conventional single-mode fiber pushed against the surface tension of a bead of water. The measured transmission changes of individual cladding mode resonances of the TFBG corresponding to these force values are of the order of 29 dB. Separate measurements of the contact angle between the surface of the water and the fiber are used to calibrate the sensor with help from the known value of surface tension for water. Once calibrated, a TFBG can be used to measure unknown forces in the same range or to measure an unknown surface tension, provided a separate force measurement is available.

2 µm Doppler wind lidar with a Tm:fiber laser-pumped Ho:YLF laser

Kohei Mizutani, Shoken Ishii, Makoto Aoki, Hironori Iwai, Ryohei Otsuka, Hirotake Fukuoka, Takayoshi Ishikawa, and Atsushi Sato

Doc ID: 314273 Received 29 Nov 2017; Accepted 02 Dec 2017; Posted 07 Dec 2017  View: PDF

Abstract: A 2 µm Ho:YLF laser end-pumped by a 1.94 µm Tm:fiber laser was developed. A laser system of ring resonator oscillator and amplifier was operated at repetition rates of 200–5000 Hz at room temperature. The Q-switched outputs were 7.4 W at 5000 Hz and 4.25 W at 200 Hz. Injection seeding was applied to the ring resonator and single-mode laser emission was obtained. The Tm:fiber laser pumped Ho:YLF laser was first used for Doppler wind lidar measurements, and wind profiles were obtained up to ranges of about 15 km in a range resolution of 96 m and an integration time of 1 second.

Evanescent field refractometry in planar optical fiber

Christopher Holmes, Alex Jantzen, Alan Gray, Paul Gow, Lewis Carpenter, Rex Bannerman, James Gates, and Peter Smith

Doc ID: 309889 Received 25 Oct 2017; Accepted 01 Dec 2017; Posted 06 Dec 2017  View: PDF

Abstract: This work demonstrates a refractometer in Integrated OpticalFiber (IOF), a new optical platform that planarizes fiber usingflame hydrolysis deposition (FHD). The unique advantage of thetechnology is its survivability in harsh environments. Theplatform is mechanically robust, can survive elevatedtemperatures approaching 1000oC and exposure to commonsolvents, including acetone, petrol and methanol. For thedemonstrated refractometer, fabrication was achieved throughwet etching an SMF-28 fiber to a diameter of 8 μm before FHDplanarization. External refractive index was monitored usingfiber Bragg gratings, written into the core of the planarizedfiber. A direct comparison to alternative fiber Bragg gratingrefractometers is made. The developed platform is shown tohave comparable sensitivities, with the added advantage ofsurvivability in harsh environments.

Real-time Fourier transformation based on bandwidth magnification of RF signal

Yan Zheng, Jilong Li, Yitang Dai, Feifei Yin, and Kun Xu

Doc ID: 312648 Received 03 Nov 2017; Accepted 01 Dec 2017; Posted 04 Dec 2017  View: PDF

Abstract: We demonstrate a novel real-time Fourier transformation (RTFT) scheme with MHz-level resolution realized by bandwidth magnification of radio frequency (RF) signal. Before the frequency-to-time mapping, the RF signal is modulated on an optical frequency comb, and then extracted by a Vernier comb filter. As a result, RF components can be separated in spectrum with greatly magnified optical bandwidth. So, even with limited dispersion provided by ordinary optical fiber, the frequency-dependent pulses can be distinguished in time domain. Experimentally, the RF signal where the frequency difference is 60 MHz is separated by around 1 -ps in time domain, equivalent to the dispersion of 1975.5 ps/GHz (247000 ps/nm), while the physical dispersion is 1500 ps/nm. Thus, based on the bandwidth magnification of RF signal, the dispersion is equivalently amplified by 165 times.

Scattering cross section modulation in photoacoustic remote sensing microscopy

Kevan Bell, Parsin Haji Reza, and Roger Zemp

Doc ID: 307975 Received 27 Sep 2017; Accepted 01 Dec 2017; Posted 01 Dec 2017  View: PDF

Abstract: Modeling and observations of large scattering cross-section modulations in absorbing optical scatterers due to a pulsed laser excitation is reported. Rapid laser-induced thermo-elastic expansion produces non-trivial perturbations to the local refractive indicies. This mechanism forms the basis of a recent non-contact photoacoustic technique known as photoacoustic remote sensing (PARS) microscopy. A time-evolution model is constructed and discussed, comparing with existing planar models, time-independent models, and experiments. Fractional scattering cross-section modulations greater than 20 times that of the unperturbed particles are predicted and observed for the first time. A non-linear acoustic enlargement effect is likewise predicted and observed. Implications of system and material properties are explored.

A differential loss, magnetic field sensor using a ferrofluid encapsulated D-shaped optical fiber

Georgios Violakis, Nikolaos Korakas, and Stavros Pissadakis

Doc ID: 308142 Received 02 Oct 2017; Accepted 01 Dec 2017; Posted 01 Dec 2017  View: PDF

Abstract: A ferrofluid encapsulated, D-shape optical fiber exhibits differential loss with respect to magnetic field placed azimuthally around its longitudinal axis, manifested in its transmission power measured. Experimental results obtained show that differential loss changes up to 12dB are measured versus magnetic field azimuthally placed with respect to the longitudinal axis of the D-shape optical fiber. Investigating the underlying physical mechanisms involved, magneto-induced refractive index and loss measurements using ferrofluid overlaid diffractive elements, reveal a differential loss mechanism associated with the relative light polarization direction and the magnetic field application direction; also used for performing modal profile simulations of ferrofluid immersed D-shape optical fiber. It is demonstrated that such an optical system can act as a magnetic field sensor with field angle and intensity sensing capabilities.

Photoacoustic and hyperspectral dual-modality endoscope

liu ning, Sihua Yang, and Da Xing

Doc ID: 308566 Received 05 Oct 2017; Accepted 01 Dec 2017; Posted 01 Dec 2017  View: PDF

Abstract: We have developed a dual-modality endoscope composed of photoacoustic (PA) and Hyperspectral imaging (HSI), capable of visualizing both structural and functional properties of bio-tissue. The endoscope’s composition and scanning mechanism was described, and the feasibility and ability of the dual-modality endoscope was verified by mimic phantom experiments. Late we demonstrated its endoscopic workability through in-vivo experiments. The experimental results showed that the proposed herein hybrid endoscope can provide optical imaging of the surface and tomography imaging for the deeper features, and oxygen saturation map of the same imaging area. We demonstrated optical-resolution photoacoustic imaging of microvascular structures and oxygen saturation map in a rabbit’s rectum. It confirmed that this dual-modality endoscope can play an important role in comprehensive clinical applications.

Observation of Spatial Optical Diametric Drive Acceleration in Photonic Lattices

Yumiao Pei, Yi Hu, Cibo Lou, Daohong song, Liqin Tang, Jingjun Xu, and Zhigang Chen

Doc ID: 312739 Received 06 Nov 2017; Accepted 01 Dec 2017; Posted 01 Dec 2017  View: PDF

Abstract: We experimentally and theoretically demonstrate a spatial diametric drive acceleration of two mutually incoherent optical beams in one dimensional optical lattices under a self-defocusing nonlinearity. The two beams, exciting the modes at the top/bottom edges of the first Bloch band and hence experiencing normal/ anomalous diffraction, can bound together and bend in the same direction during nonlinear propagation, analogous to the interplay between two objects with opposite signs of mass that breaks the Newton’s third law. Their spatial spectrum changes associated with the acceleration are analyzed for different lattice modulations. We find that the acceleration limit is determined by the beam exciting the top bandedge that reaches a saturated momentum change prior to the other pairing beam.

Cascaded four-wave-mixing in the extreme ultraviolet region

Lap Dao, Khoa Anh Tran, and Peter Hannaford

Doc ID: 309508 Received 23 Oct 2017; Accepted 30 Nov 2017; Posted 01 Dec 2017  View: PDF

Abstract: We present a detailed study of the wave-mixing process in the extreme ultraviolet region (around 30 nm) by using two collinear multiple-cycle laser pulses with incommensurate frequencies (wavelengths 1400 nm and 800 nm). The experimental data provides evidence for the coherent accumulation of wave-mixing fields and a high third-order response of the medium in this spectral range. We show that the time evolution of the mixing fields can be used to study the coherence dynamics of the free electron wave-packet with a lifetime of 200 – 750 fs.

Iodine-Stabilized Single-Frequnecy Green InGaN Diode Laser

Yi-hsi Chen, Lin Chen, Jow-Tsong Shy, and Hsiang-Chen Chui

Doc ID: 306892 Received 09 Oct 2017; Accepted 30 Nov 2017; Posted 01 Dec 2017  View: PDF

Abstract: A 520-nm InGaN diode laser can emit a mW-level, single-frequency laser beam when the applied current (1.04Ith) slightly exceeds the lasing threshold. Laser frequency was stabilized onto hyperfine transitions of iodine molecules through saturated–absorption spectroscopy. The uncertainty of frequency stabilization was approximately 8x10−9 at a 10-s integration time. The stabilized laser frequency was insensitive to diode temperature and could be finely tuned by adjusting the applied current. A single longitudinal mode operational region with diode temperature, current, and output power was investigated. The proposed compact scheme can replace conventional green-diode-pumped solid-state lasers and applied as frequency standards.

Spatiotemporal sharply autofocused dual-Airy-ring-Airy-Gaussian-vortex wavepackets

Jingli Zhuang, Xingyu Chen, Fang Zhao, Xi Peng, Dongdong Li, Liping Zhang, and Dongmei Deng

Doc ID: 309452 Received 19 Oct 2017; Accepted 29 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: Here we investigate the propagation properties of spatiotemporal sharply autofocused single-Airy-ring-Airy-Gaussian-vortex(AiRAiGV) and dual-Airy-ring-Airy-Gaussian-vortex(dAiRAiGV) wavepackets by solving (3+1) D Schr\"{o}dinger equation in free space. We can change the spatial part of the wavepackets into Airy or Gaussian distribution by choosing the different spatial distribution factors $b_s$. In particular, only when the shape of pulses is set well with appropriate temporal distribution factor $b_t$ and initial velocity $v$ in temporal domain, dAiRAiGV wavepackets can simultaneously autofocus in spatial and temporal domain and the peak intensity has been increased dozens of times at the focus more than that at the initial plane. Furthermore, properties of dAiRAiGV wavepackets with a vortex in the center and off-axis vortex pairs are also discussed.

Subwavelength wave manipulation in a thin surface-wave band-gap crystal

Zhen Gao, Wang Zhuoyuan, and Baile Zhang

Doc ID: 310067 Received 26 Oct 2017; Accepted 29 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: It has been recently reported that the unit cell of wire media metamaterials can be tailored locally to shape the flow of electromagnetic waves at deep subwavelength scales [Fabrice et al., Nature Physics 9, 55-60 (2013)]. However, such bulk structures have a thickness of at least the order of wavelength, thus hindering their applications in the on-chip compact plasmonic integrated circuits. Here, based upon a Sievenpiper “mushroom” array [Sievenpiper et al., IEEE Trans. Microwave Theory Tech. 47, 2059 (1999)] which is compatible with the standard printed circuit board technology, we propose and experimentally demonstrate the deep-subwavelength manipulation of surface waves on a thin surface-wave band-gap crystal with a thickness much smaller than the wavelength (1/40th of the operating wavelength). Functional devices including T-shaped splitter and sharp bend are constructed with good performance.

Efficient, 2-5 μm tunable CdSiP2 optical parametric oscillator pumped by a laser source at 1.57 μm

L. A. Pomeranz, John McCarthy, randy day, Kevin Zawilski, and Peter Schunemann

Doc ID: 308571 Received 04 Oct 2017; Accepted 29 Nov 2017; Posted 29 Nov 2017  View: PDF

Abstract: We report on first demonstrations of CdSiP2 (CSP) based optical parametric oscillators that are pumped by eye safe Q-switched nanosecond laser sources operating at 1.57 μm. One device reached 40% optical conversion efficiency generating 10 mJ of energy near degeneracy in the 3 micron region. Angle tuning of a similar device through the middle infrared was demonstrated with the signal and idler waves being tuned from 2.28 to 5.05 μm.

Near quantum-noise limited and absolute frequency stabilized 1083 nm single-frequency fiber laser

Qilai Zhao, Kaijun Zhou, Zisheng Wu, Changsheng Yang, Zhouming Feng, Huihui Cheng, Jiulin Gan, Mingying Peng, Zhongmin Yang, and Shanhui Xu

Doc ID: 307847 Received 25 Sep 2017; Accepted 29 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: The Earth’s magnetic field has significant effects, which can protect us from the cosmic radiation and provide navigation for biological migration. However, slow temporal variations originating in the liquid outer core invariably exist. To understand the working mechanism of the geomagnetic field and improve the accuracy of navigation systems, a high-precision magnetometer is essential to measure the absolute magnetic field. Helium optically pumping magnetometer is an advanced approach, but its sensitivity and accuracy are directly limited by the low-frequency relative intensity noise and frequency stability characteristics of light source. Here, we demonstrate a near quantum-noise limited and absolute frequency stabilized 1083 nm single-frequency fiber laser. The relative intensity noise is only 5 dB higher than the quantum-noise limit and the root-mean-square of frequency fluctuation is ~17 kHz after locked. This fiber laser could suppress the fluctuation of magnetic resonant frequency and improve the signal-to-noise ratio of the magnetic resonance signal detection.

High-throughput microchannels fabrication in fused silica by temporally shaped femtosecond laser Bessel beam assisted chemical etching

Zhi Wang, Lan Jiang, Xiaowei Li, Andong Wang, Zhulin Yao, Kaihu Zhang, and Yongfeng Lu

Doc ID: 307957 Received 26 Sep 2017; Accepted 29 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: We proposed to combine temporally shaped (double-pulse train) laser pulses with spatially shaped (Bessel beam) laser pulses. By using a temporally shaped femtosecond laser Bessel beam assisted chemical etching method, the energy deposition efficiency was improved by adjusting the pulse delay to yield a stronger material modification, and thus a higher etching depth. The etching depth was enhanced by a factor of 13 using the temporally shaped Bessel beam. The mechanism of etching depth enhancement was elucidated by localized transient free electrons dynamics-induced structural and morphological changes. Micro-Raman spectroscopy was conducted to verify the structural changes inside the material. This method enables high-throughput, high-aspect-ratio microchannels fabrication in fused silica for potential applications in microfluidics.

13dB Squeezed Vacuum States at 1550nm from 12mWexternal pump power at 775nm

Axel Schoenbeck, Fabian Thies, and Roman Schnabel

Doc ID: 309165 Received 16 Oct 2017; Accepted 28 Nov 2017; Posted 29 Nov 2017  View: PDF

Abstract: Strongly squeezed light at telecommunication wavelengths is the necessary resource for one-sided device-independent quantum key distribution via fibre networks. Reducing the optical pump power that is required for its generation will advance this quantum technology towards efficient out-of-laboratory operation. Here, we investigate the second-harmonic pump power requirement for parametric generation of continuous-wave squeezed vacuum states at 1550nm in a state-of-the-art doubly-resonant standing-wavecavity setup. We use coarse adjustment of the cavity length together with temperature fine-tuning for simultaneously achieving double resonance and quasi phase matching, and observe a squeeze factor of 13dB at 1550nm from just 12mW external pump power at 775nm. We anticipate that optimizing the cavity coupler reflectivity will reduce the external pump power to 3mW, without reducing the squeeze factor.

Polarization-insensitive and wide-incident-angle optical absorber with periodically patterned graphene-dielectric arrays

Xiujuan Zou, Gaige Zheng, Jiawei Cong, Linhua Xu, Yunyun Chen, and Min Lai

Doc ID: 309521 Received 18 Oct 2017; Accepted 28 Nov 2017; Posted 29 Nov 2017  View: PDF

Abstract: A polarization-insensitive and angle-independent graphene absorber (GA) with periodically patterned grating is demonstrated. A periodic nanocavity composed of multilayer subwavelength grating and metal substrate supports a strongly localized mode inside the cavity, where the mode helps to absorb more electromagnetic (EM) waves. The proposed GA exhibits polarization-insensitive behavior and maintains the high absorption above 90% up to a wide range of incident angle (more than 80°). We attribute the high absorption to the excitation of the cavity mode resonance (CMR) and magnetic resonance (MR) for the TE and TM polarizations, respectively. The proposed graphene absorber has potential applications in the design of various devices such as optical modulators or tunable absorption filters because of its remarkable angle-insensitive absorption performance.

Nonlinear absorption and temperature-dependent fluorescence of perovskite FAPbBr3 nanocrystal

Lan Yang, Ke We, Zhongjie Xu, Feiming Li, Runze Chen, Xin Zheng, Xiang'ai Cheng, and Tian Jiang

Doc ID: 314004 Received 21 Nov 2017; Accepted 28 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: Recent progress in solar cell and light emitting devices makes halide perovskite a research hot-spot in optics. In this paper, the nonlinear absorption and fluorescence properties of FAPbBr3 nanocrystal, one typical organometallic halide perovskite, have been investigated via Z-scan measurements and density-dependent photoluminescence (PL) spectrum. The FAPbBr3 nanocrystal exhibits nonlinear absorption under the excitation of 800 nm, whose photon energy is below the bandgap of FAPbBr3. The significant absorption is experimentally confirmed to be induced by two photon absorption (TPA) and the TPA coefficient is measured to be ~0.0042 cm∕GW. Moreover, the PL induced by TPA in FAPbBr3 nanocrystal shows different temperature-dependent behaviours in the range from 90 K to 350 K. The peaks of PL spectrum remain nearly constant at 100 K ~ 160 K, with a very shallow trough at around 150 K, while a linear blue-shift (0.496 meV/K) of the spectrum is observed when temperature is above 160 K. These temperature-dependent fluorescence behaviors can be ascribed to the structural phase transition at about 150 K and the contribution of thermal expansion. Moreover, the exciton binding energy of 62.4 meV and the optical phonon energy of 15.3meV are also extracted from the temperature-dependent PL data.

Broadband near-infrared antireflection coatings fabricated by three dimensional direct laser writing

Yanzeng Li, Daniel Fullager, Edison Angelbello, Darrell Childers, Glenn Boreman, and Tino Hofmann

Doc ID: 308273 Received 03 Oct 2017; Accepted 28 Nov 2017; Posted 04 Dec 2017  View: PDF

Abstract: Three-dimensional direct laser writing via two photon polymerization is used to fabricate anti-reflective structured surfaces composed of sub-wavelength conicoid features optimized to operate over a wide bandwidth in the near-infrared range from 3700 cm-1 to 6600 cm-1 (2.7 to 1.52 μm). Analytic Bruggemann effective medium calculations are used to predict nominal geometric parameters such as the fill factor of the constitutive conicoid features of the anti-reflective structured surfaces presented here. The performance of the anti-reflective structured surfaces was investigated experimentally using infrared transmission measurements. An enhancement of the transmittance by 1.35% to 2.14% over a broadband spectral range from 3700 cm-1 to 6600 cm-1 (2.7 to 1.52 μm) was achieved. We further report on finite-element-based reflection and transmission data using three-dimensional model geometries for comparison. A good agreement between experimental results and the finite-element-based numerical analysis is observed once as-fabricated deviations from the nominal conicoid forms are included in the model. Three-dimensional direct laser writing is demonstrated here as an efficient method for the fabrication and optimization of anti-reflective structured surfaces designed for the infrared spectral range.

Non-diffracting beams for label-free imaging through turbid media

Harel Nagar, Elad Dekel, Dror Kasimov, and Yael Roichman

Doc ID: 312499 Received 07 Nov 2017; Accepted 28 Nov 2017; Posted 04 Dec 2017  View: PDF

Abstract: We propose a new method to image through dynamically changing turbid media based on scanning of non-diffractive laser beams. We use computer generated holograms to create Airy beams and compare quantitatively the characteristics of their propagation in clear and turbid media. Imaging contrast is achieved by relative reflection of the scanned beams from the imaged surface. We implement our method to demonstrate experimentally our ability to image a chromium surface on a glass slide through 270 um of highly scattering milk/water mixtures with a resolution of several microns.

TE-polarized design for metallic slit lenses: a way to deep-subwavelength focusing over a broad wavelength range

Yechuan Zhu, Weizheng Yuan, Wenli Li, Hao Sun, Kunlun Qi, and Yiting Yu

Doc ID: 313047 Received 08 Nov 2017; Accepted 27 Nov 2017; Posted 04 Dec 2017  View: PDF

Abstract: Slit arrays based on noble metals have been widely proposed as planar transverse-magnetic-(TM)-lenses, illuminated by a linearly polarized light with the polarization perpendicular to slits and implementing the focusing capability beyond the diffraction limit. However, due to intrinsic plasmonic losses, these TM-lenses cannot work efficiently in the ultraviolet wavelengths. In this letter, taking advantage of the unique transmission through metallic slits not involving plasmonic losses, a metallic slit array with transverse-electric (TE) polarized design is proposed, showing for the first time, to the best of our knowledge, the realization of sub-diffraction-limit focusing for ultraviolet light. Additionally, in contrast to the situations of TM-lenses, a wider slit leads to a greater phase delay and much larger slits can be arranged to construct the TE-lenses, which is quite beneficial for practical nanofabrication. Furthermore, deep-subwavelength focusing can be achieved by utilizing the immersing technology.

Plasmon mediated inverse Faraday effect in graphene - dielectric - metal structure

Igor Bychkov, Dmitry Kuzmin, Valentine Tolkachev, Pavel Plaksin, and Vladimir Shavrov

Doc ID: 311254 Received 31 Oct 2017; Accepted 27 Nov 2017; Posted 29 Nov 2017  View: PDF

Abstract: The present Letter shows the features of inverse Faraday effect in the graphene-dielectric-metal (GDM) structure. The constants of propagation and attenuation of the surface plasmon-polariton modes are calculated. The effective magnetic field induced by surface plasmon modes in the dielectric due to the inverse Faraday effect is estimated to reach above 1 tesla. The possibility to control the distribution of the magnetic field by chemical potential of graphene is shown. The concept of strain-driven control of the inverse Faraday effect in the structure has been proposed and as well investigated.

Fabrication of helical photonic structures with submicrometer axial and spatial periodicities following ‘inverted umbrella’ geometry through phase controlled interference lithography

Saraswati Behera, Swagato Sarkar, and Joby Joseph

Doc ID: 306516 Received 05 Sep 2017; Accepted 27 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: In this paper, we report for the first time a phase SLM based interference lithography approach for the realization of hexagonally packed helical photonic structures with submicrometer scale spatial as well as axial periodicity over large area. A phase only spatial light modulator is used to electronically generate six phase controlled plane beams. These six beams from the front side and a direct central backside beam are used together in an “inverted umbrella” geometry setup to realize the desired submicrometer axial periodic chiral photonic structures through interference lithography. The realized structures with 650 nm spatial and 353 nm axial periodicities on negative photoresist can be used as an optical filter and refractive index sensor as evidenced from the FDTD based simulation study on its optical properties. Further, the fabricated templates can be transferred to metals such as silver or aluminum for the realization of metamaterial based broadband circular polarizer ranging from 1-3.5 µm NIR spectra.

Polarization control of terahertz radiation from two-color femtosecond gas breakdown plasma

Olga Kosareva, Mikhail Esaulkov, Nikolay Panov, Vera Andreeva, Daniil Shipilo, Petr Solyankin, Ayhan Demircan, Ihar Babushkin, Vladimir Makarov, Uwe Morgner, Alexander Shkurinov, and Andrei Save'ev

Doc ID: 307555 Received 22 Sep 2017; Accepted 26 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: We individually control polarizations of the 800-nm and 400-nm beams, which form the two-color femtosecond plasma filament in air irradiating linear-to-elliptical THz signal. We detected the threshold-like appearance of THz ellipticity at the angle of ~85º between the fundamental and the second harmonic field polarization directions. The simulations confirm the abrupt change of THz polarization and reveal that the weak ellipticity of the second harmonic is sufficient to generate essentially elliptical THz radiation.

Absorption of laser plasma in competition with oscillation currents for terahertz spectrum

Xiaolu Li, Ya Bai, Na Li, and Peng Liu

Doc ID: 309865 Received 24 Oct 2017; Accepted 26 Nov 2017; Posted 29 Nov 2017  View: PDF

Abstract: We generate terahertz radiation in a supersonic jet of nitrogen molecules pumped by intense two-color laser pulses. The tuning of terahertz spectra from blue-shift to red-shift is observed by increasing laser power and stagnation pressure, and the red-shift range is enlarged with the increased stagnation pressure. Our simulation reveals that the plasma absorption of the oscillation currents and expanded plasma column owing to increased laser intensity and gas number density are crucial factors in recurrence of the red-shift of terahertz spectra. The findings disclose the microscopic mechanism of terahertz radiation and present a controlling knob for the manipulation of broadband terahertz spectrum from laser plasma.

Quadrature squeezing of higher-order sideband spectrum in cavity optomechanics

Shaopeng Liu, Wen-Xing Yang, Zhonghu Zhu, Tao Shui, and Ling Li

Doc ID: 309605 Received 19 Oct 2017; Accepted 26 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: We propose an efficient scheme to generate quadrature squeezing of higher-order sideband spectrum in an optomechanical system. That is achieved by exploiting a well-established optomechanical circumstance,where a second-order nonlinearity is embedded into the optomechanical cavity driven by a strong control field and a weak probe pulse. Using experimentally achievable parameters, we demonstrate that thesecond-order nonlinearity intensity and the frequency detuning of control field allow us to modify the amplitude of higher-order sidebands and improve the amount of squeezing of higher-order sideband spectrum. Furthermore, in the presence of a strong second-order nonlinearity, an optimizing quadrature squeezing of higher-order sideband spectrum can be achieved, which provides a practical opportunity to design the squeezed frequency combs and others precision measurement.

Dispersion-managed Ho-doped fiber laser mode-lockedwith graphene saturable absorber

Maria Pawliszewska, Tadeusz Martynkien, aleksandra przewłoka, and Jaroslaw Sotor

Doc ID: 309690 Received 20 Oct 2017; Accepted 25 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: In this work we demonstrate an all-fiber holmium-doped laser operating in the stretched-pulse regime. As a result of dispersion management, the laser is capable of generating 190 fs pulses with bandwidth of 53.6 nm. The pulses centered at 2060 nm reach 2.55 nJ of energy. Mode-locking is achieved with multilayer graphene saturable absorber. The paper also presents measurement of group velocity dispersion of active (Nufern SM-HDF-10/130), passive (SMF28), and dispersion compensating (Nufern UHNA4) fibers in 1.8 - 2.1 μm range. This is the first report on an all-fiber, stretched-pulse laser operating beyond 2 μm with nanomaterial-based saturable absorber.

Doppler-free Fourier transform spectroscopy

Samuel Meek, Arthur Hipke, Guy Guelachvili, Theodor Haensch, and Nathalie Picque

Doc ID: 308719 Received 20 Oct 2017; Accepted 25 Nov 2017; Posted 29 Nov 2017  View: PDF

Abstract: Sub-Doppler broadband multi-heterodyne spectroscopy is proposed and experimentally demonstrated. Using two laser frequency combs of slightly different repetition frequencies, we have recorded Doppler-free two-photon dual-comb spectra of atomic rubidium resonances of a width of 6 MHz, while simultaneously interrogating a spectral span of 10 THz. The atomic transitions are uniquely identified via the intensity modulation of the observed fluorescence radiation. These results, which -to our knowledge- represent the first demonstration of Doppler-free Fourier transform spectroscopy, extend the range of applications of broadband spectroscopy towards precision nonlinear spectroscopy.

Silicon-on-insulator microring resonator sensor based on amplitude comparison sensing function

Wenjian Yang, SHIJIE SONG, Xiaoke Yi, Suen Xin Chew, Liwei Li, and Linh Nguyen

Doc ID: 308638 Received 05 Oct 2017; Accepted 25 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: A novel highly sensitive integrated sensor based on silicon-on-insulator microring resonator is proposed and experimentally demonstrated. To achieve a fast-response and cost-effective sensing system, the new structure establishes an amplitude comparison sensing function (ACSF), which monitors the optical power from both through port and drop port of an add-drop microring resonator simultaneously. A highly enhanced linear relationship between the resonant wavelength shift and the ACSF value is achieved with R-squared value over 0.99. Meanwhile, the structure can also eliminate the unexpected power fluctuation of the input laser. Experiment demonstrates an almost constant ACSF with only ±0.9% discrepancy while the laser power is varied between 0 dBm to -7 dBm.

Anisotropy of Nonlinear Optical Absorption of LBO Crystals at 355 nm

Oleg Vershinin, Aleksey Konyashkin, and Oleg Ryabushkin

Doc ID: 310110 Received 27 Oct 2017; Accepted 24 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: Dependence of nonlinear-optical absorption coefficient on intensity and polarization of pulsed laser radiation at 355 nm was investigated for LBO crystal using piezoelectric resonance laser calorimetry

Massive ordering and alignment of cylindrical micro-objects by photovoltaic optoelectronic tweezers

Iris Elvira, Juan Muñoz-Martínez, Álvaro Barroso, Cornelia Denz, José Bruno Ramiro, Angel Garcia-Cabañes, Fernando Agullo-Lopez, and Mercedes Carrascosa

Doc ID: 309968 Received 25 Oct 2017; Accepted 23 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: Optical tools for manipulation and trapping of micro- and nano-objects is a fundamental issue for many applications in nano and biotechnology. This work reports on the use of one of such methods, known as photovoltaic optoelectronics tweezers to orientate and organize cylindrical micro-crystals, specifically elongated zeolite L, on the surface of Fe-doped LiNbO3 crystal plates. Patterns of aligned zeolites have been achieved through the forces and torques generated by the bulk photovoltaic effect. The alignment patterns with zeolites parallel or perpendicular to the substrate surface are highly dependent on the features of the light distribution and the crystal configuration. Moreover, dielectrophoretic chains of zeolites with lengths up to 100 µm have been often observed. The experimental results of zeolite trapping and alignment have been discussed and compared together with theoretical simulations of the evanescent photovoltaic electric field and the dielectrophoretic potential. They demonstrate the remarkable capabilities of the optoelectronic photovoltaic method to orientate and pattern anisotropic microcrystals. The combined action of patterning and alignment offers an unique tool to prepare functional nanostructures with potential applications in a variety of fields such as non-linear optics, or plasmonics.

Geometrical optimization of nanostripes for surfaceplasmon excitation: an analytical approach

Thomas Grosges and Dominique Barchiesi

Doc ID: 309893 Received 24 Oct 2017; Accepted 23 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: We give a simple tool for the optimization of the dimensions of a metallicnanostrip illuminated at a given wavelength under normal incidence,to get a maximum of the electromagnetic field amplitude in the nanostrip.We propose an analytical formula that gives the widths and the heights of the series of nanostripes that produce field enhancement.The validity of the analytical formula is checked by using Finite Element Method. This design of nanostrip could be useful for sensors and thermally active components.

Fabrication of optical vortices lattices based on holographic polymer dispersed liquid crystal films

Andy Y.-G. Fuh, YI LIN TSAI, Ching Han Yan, and Shing Trong Wu

Doc ID: 310072 Received 26 Oct 2017; Accepted 23 Nov 2017; Posted 04 Dec 2017  View: PDF

Abstract: This study demonstrates optical vortices lattices based on holographic polymer stabilized liquid crystal films. The fabrication uses a phase only reflective spatial light modulator with numerically calculated phase profiles loaded on it to simplify the multi-helical-wave interference. The beam profiles of the diffraction beams are simulated using Fourier transformation and compared with the experimental results. The topological charges of the 1st order diffraction beams reconstructed from the HPDLC films are examined using Michelson interferometer.

Stable vortex soliton in nonlocal media with orientational nonlinearity

Yana Izdebskaya, Vladlen Shvedov, pawel jung, and Wieslaw Krolikowski

Doc ID: 308874 Received 11 Oct 2017; Accepted 23 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: We report on the first experimental observation of stable vortex solitons in nematic liquid crystals with nonlocal nonlinear reorientational response. We show how these nonlinear vortex beams can be formed and confined in extraordinary optical waves by employing the cell with no lateral boundary conditions and the application of an external magnetic field that effectively controls the molecular direction and propagation of the self-trapped beams. We also find that these vortex solitons can be generated in certain ranges of the input beam power.

Orbital Angular Momentum Generation via Spiral Phase Microsphere

Yan Zhou, Gao Hui, Jinghua Teng, Xiangang Luo, and Minghui Hong

Doc ID: 309301 Received 17 Oct 2017; Accepted 23 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: Vortex beam carrying orbital angular momentum (OAM) attracts much attention in many research fields for its special phase and intensity distributions. In this letter, a novel design called the spiral phase microsphere (SPMS) is proposed for the first time which can convert incident plane wave light into the focused vortex beam that carries OAM with different topological charges l = ±1 and ±2. The vortex beam generation is verified by a self-interfered modification of the SPMS. Generation of the vortex beams by the SPMS irradiated by a single-wavelength incident light is studied using the CST MICROWAVE STUDIO simulation. SPMS provides a new approach to achieve high-efficiency and high-integrated photonic applications related with OAM.

Selective generation of Lamb modes by moving CW laser

Zheng Li, Alexey Lomonosov, Chenyin Ni, Bing Han, and Shen Zhong-Hua

Doc ID: 308314 Received 02 Oct 2017; Accepted 23 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: This paper focused on the selectively non-contact generation of Lamb wave modes in plates by using a continuous wave (CW) laser moving along sample surface. Compared with the generated Lamb waves with broadband, multiple modes (the existence of at least two modes at any given frequency) excited by pulsed laser, the desired single narrowband mode of Lamb wave can be generated by a moving CW laser, as long as the scanning speed matches with the phase velocity of the mode. Moreover, the dispersion curves of Lamb wave can be obtained directly from the power spectrum of the time-domain signal recorded at each laser moving speed. Single A0 mode excitation, coupled resonance phenomenon of A0 mode and S0 mode, single S0 mode excitation and high order modes appeared successively as scanning speed increases. Especially, the excitation of the pure single S0 mode can be realized which is suitable for propagation in the case of liquid loading. It is first proposed to realize the selection of a single Lamb wave mode by using the CW laser scanning method, which provides a brand-new way for the laser ultrasonic excitation.

Super pulses of orbital angular momentum in fractional-order spiroid vortex-beams

Alexander Volyar and Egorov Yuriy

Doc ID: 308262 Received 02 Oct 2017; Accepted 22 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: We consider optical properties of Hypergeometric-Gaussian beam compositions with spiral-like intensity and phase distributions that are called the spiroid beams. Their orbital angular momentum as a function of a fractional-order topological charge has a chain of super-pulses (bursts and dips).The form of the super-pulses can be controlled by the spiral parameters. Such a phenomenon can be used in optical switches and triggers for optical devices and communication systems.

Sandwiched Transparent Epsilon-Near-Zero Metamaterial Screen

Rui Yang, Pei Yang, Yongchao Chen, Jiacheng Li, and Zhenya Lei

Doc ID: 308668 Received 09 Oct 2017; Accepted 22 Nov 2017; Posted 22 Nov 2017  View: PDF

Abstract: We propose a sandwiched transparent epsilon-near-zero (ENZ) metamaterial screen to release the obliquely incident electromagnetic fields. More specifically, the transmission properties through ENZ metamaterials are investigated when incorporated with an interlayer of a meta-surface having periodic complementary spiral-resonator-matrixes. We show that both TE- and TM-polarized electromagnetic waves are capable of penetrating the ENZ metamaterials under a wide-angle range of illuminations, and the greatly enhanced transmissions are turning out to be frequency dispersionless for different polarized electromagnetic fields with different incident angles. Our design, breaking the notion of the angular filter of ENZ metamaterials, should readily be applied to other extreme-parameter materials and pave the way to explore more unexpected transmission properties of these metamaterials.

Modal Instability Induced By Stimulated Raman Scattering In High Power Yb-Doped Fiber Amplifiers

Mahdi Shayganmanesh, Kamran Hejaz, Reza RezaeiNasirabad, Ali Roohforouz, saeed azizi, ali abedinajafi, and Vahid Vatani

Doc ID: 309553 Received 23 Oct 2017; Accepted 22 Nov 2017; Posted 22 Nov 2017  View: PDF

Abstract: Modal instability (MI) and stimulated Raman scattering (SRS) are the main obstacles in power scaling of fiber lasers and amplifiers. In the power scaling of a high power Yb-doped master oscillator power amplifier (MOPA) system, new type of MI has been occurred. Experimentally, it is shown that just at the onset of SRS effect, MI takes place and degradation of the beam quality is observed. By the spectra and beam quality measurements it is revealed that this type of MI, can be mitigated firmly by suppressing the SRS effect in high power Yb-doped fiber amplifiers.

Broadband Non-volatile Photonic Switching Based on Optical Phase Change Materials -- Beyond the Classical Figure-of-Merit

Yifei Zhang, Juejun Hu, Qihang Zhang, Junying Li, Richard Soref, and Tian Gu

Doc ID: 312323 Received 31 Oct 2017; Accepted 22 Nov 2017; Posted 22 Nov 2017  View: PDF

Abstract: In this letter, we propose and theoretically analyze a broadband, non-volatile on-chip switch design in the telecommunication C-band with record low loss and crosstalk. The unprecedented device performance builds on two key innovations: 1) a new optical phase change material (O-PCM) Ge2Sb2Se4Te1 (GSST), which exhibits significantly reduced optical attenuation compared to traditional O-PCMs; and 2) a non-perturbative design which enables low-loss device operation beyond the classical figure-of-merit (FOM) limit. We further demonstrate that the 1-by-2 and 2-by-2 switches can serve as basic building blocks to construct non-blocking and non-volatile on-chip switching fabric supporting arbitrary numbers of input and output ports.

High efficiency 2 μm Tm:YAP laser with a compact mechanical Q-switch

Brian Cole, Lew Goldberg, and Alan Hays

Doc ID: 309502 Received 18 Oct 2017; Accepted 22 Nov 2017; Posted 04 Dec 2017  View: PDF

Abstract: We describe a compact, highly efficient, diode-pumped, mechanically Q-switched Tm:YAP laser operating near 2 μm. The Q-switch, based on a torsion spring resonant mirror scanner, had negligible optical loss and requiredvery low electrical drive power. At a 10 kHz pulse repetition frequency, the laser generated an average output power of 10.5 W at 1.94μm, Q-switched pulse energy of 1.05 mJ, pulse length of 31 ns, and a peak power of 34kW. The Q-switched laser exhibited maximum optical and electrical efficiencies of 51% and 26%, respectively

Fiber Bragg grating fabricated in micro-single-crystal sapphire fiber

Shuo Yang, Daniel Homa, Gary Pickrell, and Anbo Wang

Doc ID: 309905 Received 24 Oct 2017; Accepted 22 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: This Letter introduces a fiber Bragg grating in a micro-single-crystal sapphire fiber (micro-SFBG) for sensing applications in high temperature and harsh environments. The FBG was fabricated by a point-by-point method via an IR-femtosecond laser in a large diameter sapphire fiber that was then wet-hot acid etched to achieve microfiber size, which culminated in fabricating and characterizing a 9.6 μm-diameter micro-SFBG. The refractive index measurement ranging from 1 to 1.75 and temperature measurement from room temperature to 1400℃ are also reported.

CEP dependence of Signal and Idler upon Pump-Seed synchronization in optical parametric amplifiers

Giulio Maria Rossi, Lu Wang, Roland Mainz, Huseyin Cankaya, Giovanni Cirmi, and Franz Kaertner

Doc ID: 307051 Received 13 Sep 2017; Accepted 22 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: We present a comprehensive study of the effect of Pump-Seed timing fluctuations on the carrier-envelope phase (CEP) of Signal and Idler pulses emerging from an OP(CP)A. A simple analytical model is derived in order to provide an intuitive explanation of the origin of CEP fluctuations, while split-step simulations are performed to cover a broad range of different seeding schemes. Finally we compare the simulation results with real observations of the CEP of the Idler pulses generated by an OPA. The quantitative model presented provides a key tool for designing next generation of low noise CEP-stable OP(CP)A-based sources.

Flexible pulse-stretching for swept source at 2.0 µm using free-space angular-chirp-enhanced delay

Sisi Tan, Xiaoming Wei, Jianglai Wu, lingxiao yang, Kevin Tsia, and Kenneth Kin-Yip Wong

Doc ID: 309098 Received 16 Oct 2017; Accepted 22 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: Dispersive pulse-stretching at 2.0 µm has long been hindered by the high intrinsic optical loss from conventional dispersive media. Here, a flexible pulse-stretching technique at 2.0 µm is demonstrated over a broad bandwidth with large-scale dispersion and low intrinsic optical loss. It employs the newly proposed pulse-stretching scheme, namely, free-space angular-chirp-enhanced delay (FACED). Both normal and anomalous temporal dispersion (up to ±500 ps/nm) with low intrinsic loss (< 6 dB) over a spectral bandwidth of ~84 nm at 2.0 µm is obtained with low nonlinear effects. Based on this method, optical wavelength-swept source at 2.0 µm is realized and applied to spectrally-encoded imaging at a line-scan rate of ~19 MHz, proving the potential of this pulse-stretching technique for continuous single-shot measurements at the 2.0-µm wavelength regime, particularly for optical microscopy and spectroscopy.

Visible Light Optical Coherence Microscopy of the Brain with Isotropic Femtoliter Resolution In Vivo

Conrad Merkle, Shau Poh Chong, Aaron Kho, Jun Zhu, Alfredo Dubra, and Vivek Srinivasan

Doc ID: 308468 Received 02 Oct 2017; Accepted 21 Nov 2017; Posted 30 Nov 2017  View: PDF

Abstract: Most flying-spot Optical Coherence Tomography (OCT) and Optical Coherence Microscopy (OCM) systems use a symmetric confocal geometry, where the detection path retraces the illumination path starting from and ending with the spatial mode of a single mode optical fiber. Here, we describe a visible light OCM instrument that breaks this symmetry to improve transverse resolution without sacrificing collection efficiency. This was achieved by overfilling a water immersion objective on the illumination path, while maintaining a conventional Gaussian mode detection path (1/e2 intensity diameter ~0.82 Airy disks), enabling ~1.1 μm full-width at half-maximum (FWHM) transverse resolution. At the same time, a ~0.9 μm FWHM axial resolution in tissue, achieved by a broadband visible light source, enabled femtoliter volume resolution. We characterized this instrument according to paraxial coherent microscopy theory, and finally, used it to image the meningeal layers, intravascular red blood cell-free layer, and myelinated axons in the mouse neocortex in vivo through the thinned skull.

Localized Excitation of Polarized Light Emission by Cathodeluminescence Spectroscopy

Yuhui Hu, Fei Chen, Yajun Gao, Xiang Xiong, Ruwen Peng, and Mu Wang

Doc ID: 312974 Received 08 Nov 2017; Accepted 21 Nov 2017; Posted 29 Nov 2017  View: PDF

Abstract: Surface plasmons, the resonance of free electrons on the metal-air interface, may strongly interact with light and generate some extraordinary optical effects. Instead of using conventional planar light excitation, here we excite surface plasmons with focused electron beam on metallic nanostructures with different geometrical symmetry. With the help of polarizer and filter in the detection system, we obtain cathodeluminescence (CL) images with different polarization at certain wavelength. The maxima in the CL images show that the focused electron beam may efficiently excite luminescence with different polari- zation at different spots. Comparing with the data collected on the structures with specific geometrical symmetry, we demonstrate that the polarization of the emitted light depends on both the structural symmetry and the excitation location. We suggest that this work is enlightening to understand the relationship between surface plasmon resonance on the structure and emi- ssion of CL with different polarizations.

Phase modulator mode based on pre-transitional effect of antiferroelectric liquid crystals

Ken Ishikawa and Zhengyu Feng

Doc ID: 312468 Received 02 Nov 2017; Accepted 21 Nov 2017; Posted 04 Dec 2017  View: PDF

Abstract: We demonstrate a novel phase only modulation mode based on the pre-transitional effect of the antiferroelectric liquid crystal. 2 pi phase modulation without changing the polarization state of the incident light is achieved with a low field(1.8 V/mm). This phase modulation mode also shows ultrafast response time(less than 300 microseconds) and a uniform optical texture with easy fabrication process. This phase modulator can be applied to laser beam steering, virtual reality and hologram etc. in the future.

Magnetometry using fluorescence of sodium vapor

Tingwei Fan, Lei Zhang, Xuezong Yang, Shenzhen Cui, Tianhua Zhou, and Yan Feng

Doc ID: 307515 Received 20 Sep 2017; Accepted 21 Nov 2017; Posted 22 Nov 2017  View: PDF

Abstract: Magnetic resonance of sodium fluorescence is studied with varying laser intensity, duty cycle, and field strength. A magnetometer based on sodium vapor cell filled with He buffer gas is demonstrated, which uses a single amplitude-modulated laser beam. With a 589 nm laser tuned at D1 or D2 line, the magnetic field is inferred from the variation of fluorescence. A magnetic field sensitivity of 150 pT/√Hz is achieved at D1 line. The work is an important step towards sensitive remote magnetometry with mesospheric sodium.

Wavelength-Modulated Planar Laser-Induced Fluorescence for Imaging Gases

Garrett Mathews and Christopher Goldenstein

Doc ID: 308901 Received 12 Oct 2017; Accepted 19 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: This work presents the development of wavelength-modulated planar laser-induced fluorescence (WM-PLIF) and its initial application to infrared imaging of carbon monoxide in a laminar flame. A continuous-wave quantum-cascade laser producing 50 mW near 4.8 μm was injection-current modulated at 1 kHz and scanned across the P(20) transition of CO at 20 Hz. The corresponding infrared-laser-induced fluorescence was imaged orthogonal to the laser sheet using a high-speed IR camera operating at a frame rate of 28 kFPS, and digital lock-in detection of the WM-PLIF 1st-harmonic signal (S_F,1f) was performed to provide high-fidelity, background-free imaging of CO with a measurement bandwidth of 100 Hz. Images of the peak-S_F,1f signal are presented for a laminar CO-H_2 diffusion flame in air at atmospheric pressure. We demonstrate that this technique is sensitive enough to image nascent CO in flames and present a strategy for simulating the WM-PLIF harmonic signals.

Efficient diode-pumped Er:KLu(WO4)2 laser at ~1.61 µm

Josep Maria Serres, Pavel Loiko, Venkatesan Jambunathan, Xavier Mateos, Vladimir Vitkin, Antonio Lucianetti, Tomas Mocek, Magdalena Aguilo, Francesc Diaz, Uwe Griebner, and Valentin Petrov

Doc ID: 309941 Received 25 Oct 2017; Accepted 19 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: We report on an efficient diode-pumped continuous-wave Erbium-doped monoclinic double tungstate laser. It is based on a 1 at.% Er3+:KLu(WO4)2 (Er:KLuW) crystal cut along the Ng optical indicatrix axis. The Er:KLuW microchip laser, diode-pumped at 0.98 µm, generates 268 mW at 1.610 µm with a slope efficiency of 30%. The output is linearly polarized (E || Nm) and the laser beam is nearly diffraction-limited. Spectroscopic properties of Er3+ in KLuW are also presented. The maximum σSE = 3.0×10-20 cm2 is at ~1.535 µm for E || Nm. The microchip Er:KLuW laser outperforms the commercial Er,Yb:glass.

Flexible design method for freeform lenses with an arbitrary lens contour

Karel Desnijder, Peter Hanselaer, and Youri Meuret

Doc ID: 308074 Received 04 Oct 2017; Accepted 19 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: A method is presented that allows to design freeform lenses with an arbitrary contour in a flexible and robust manner. The method is based on the generation of two equi-flux grids representing the source and target beams, with two separate curl-free mappings from an equi-spatial rectangular grid. Because the source and target grids are generated independently from one another, one can map arbitrary complex source beams with a certain contour onto arbitrary complex target beams within another contour, with high convergence probability. The method is illustrated by calculating a triangular freeform lens that reshapes a triangular beam from a Lambertian source into a uniform pentagonal irradiance distribution on a target plane.

Intensity modulation of terahertz bandpass filter: utilizing image currents induced on MEMS reconfigurable metamaterials

Fangrong HU, yixing fan, Xiaowen Zhang, wenying jiang, YUANZHI CHEN, Li Peng, xianhua yin, and Wentao Zhang

Doc ID: 309927 Received 25 Oct 2017; Accepted 19 Nov 2017; Posted 27 Nov 2017  View: PDF

Abstract: We experimentally demonstrated a tunable terahertz (THz) bandpass filter based on microelectromechanical systems (MEMS) reconfigurable metamaterials (MMs). The unit cell of the filter consists of two split-ring-resonators (SRRs) and a movable bar. Initially, the movable bar situates at the center of the unit cell and the filter has two passbands whose central frequencies locating at 0.65 THz and 0.96 THz, respectively. The intensity of two passbands can be actively modulated by the movable bar, and a maximum modulation depth of 96% is achieved at 0.96 THz. The mechanism of tunability is investigated using the finite-integration-time-domain (FITD) method. The result shows that the image currents induced on the movable bar are opposite to the resonance currents induced on the SRRs, and thus weakens the oscillating intensity of the resonance currents. This scheme paves a way to dynamically control and switch the THz wave at some constant frequencies utilizing induced image currents.

Modeling the sensitivity dependence of silicon-photonics-based ultrasound detectors

Shai Tsesses, Daniel Aronovich, Assaf Grinberg, Evgeny Hahamovich, and Amir Rosenthal

Doc ID: 307071 Received 13 Sep 2017; Accepted 17 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: With recent advances in optical technology, interferometric sensing has grown into a highly versatile approach for ultrasound detection, with many interferometric detectors relying on optical waveguides to achieve high levels of sensitivity and miniaturization. In this letter, we establish a practical model for assessing the sensitivity of silicon-photonics waveguides to acoustic waves. The analysis is performed for different polarizations, waveguide dimensions, and acoustic wave types. Our model was validated experimentally, by measuring the sensitivities of the two polarization modes in a silicon strip waveguide. Both the experimental results and theoretical prediction show that the TM polarization achieves a higher sensitivity and suppression of surface acoustic waves compared to the TE polarization.

Chromatic aberration compensation in numerical reconstruction of digital holograms by Fresnel-Bluestein propagation

Diego Zuluaga, Daniel Velasquez Prieto, and Jorge Garcia-Sucerquia

Doc ID: 307159 Received 14 Sep 2017; Accepted 17 Nov 2017; Posted 22 Nov 2017  View: PDF

Abstract: In this letter, we present a method for chromatic compensation in numerical reconstruction of digitally recorded holograms based on the Fresnel-Bluestein propagation. The proposed technique is applied to correct the chromatic aberration that arises in the reconstruction of RGB holograms of both millimeter- and micrometer-sized objects. The results show the feasibility of this strategy to remove the wavelength dependence of the size of the numerical propagated wavefields.

Off-axis tilt compensation in common-path digital holographic microscopy based on hologram rotation

Dingnan Deng, Weijuan Qu, Wenqi He, Yu Wu, Xiaoli Liu, and Xiang Peng

Doc ID: 304385 Received 14 Aug 2017; Accepted 16 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: We present a simple and effective compensation method for the off-axis tilt in common-path digital holographic microscopy (CPDHM) by introducing a rotating operation on the hologram. The proposed method mainly requires a digital reference hologram (DRH) which is a rotation version of the original one, it’s assumed to be easy to obtain by rotating the specimen’s hologram 180°. In this way, the off-axis tilt could be removed by subtracting the retrieved phase of DRH from the retrieved phase of original hologram, but without any complex spectrum centering judgement, fitting procedures or prior knowledge of the system. This highly automatic and efficient performance makes our approach available for real-time quantitative phase imaging (QPI). Some experimental results about a micro-lens array and a phase plate are provided to demonstrate the feasibility and effectiveness of the proposed method.

Kilohertz binary phase modulator for pulsed laser sources using a digital micromirror device

Maximilian Hoffmann, Ioannis Papadopoulos, and Benjamin Judkewitz

Doc ID: 309467 Received 19 Oct 2017; Accepted 16 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: The controlled modulation of an optical wavefront is required for aberration correction, digital phase conjugation or patterned photostimulation. For most of these applications it is desirable to control the wavefront modulation at the highest rates possible. The digital micromirror device (DMD) presents a cost-effective solution to achieve high-speed modulation and often exceeds the speed of the more conventional liquid crystal spatial light modulator, but is inherently an amplitude modulator. Furthermore, spatial dispersion caused by DMD diffraction complicates its use with pulsed laser sources, such as those used in nonlinear microscopy. Here we introduce a DMD-based optical design that overcomes these limitations and achieves dispersion-free high-speed binary phase modulation. We show that this phase modulation can be used to switch through binary phase patterns at the rate of 20 kHz in two-photon excitation fluorescence applications.

Experimental study of the mode instability onset threshold in high-power FA-LPF lasers

Marie-Alicia Malleville, Romain Dauliat, Aurélien Benoit, Baptiste Leconte, dia darwich, Rémi du Jeu, Raphael Jamier, Kay Schuster, and Philippe Roy

Doc ID: 308250 Received 29 Sep 2017; Accepted 16 Nov 2017; Posted 16 Nov 2017  View: PDF

Abstract: We report here on an experimental investigation of the temporal behavior of transverse mode instabilities into “Fully Aperiodic Large-Pitch Fibers” (FA-LPFs) operated in high-power CW laser configuration. To ensure an effective transverse single-mode emission into FA-LPFs, a perfect index-matching between the active core and the background cladding materials (∆n=0) is required. The original design of such fibers enables an effective transverse single-mode emission by strengthening the HOMs delocalization out of the gain region even for high heat load levels, consequently leading to the improvement of the beam spatial quality. The study was conducted over fibers of various gain region diameters – from 58 to 100 µm for a refractive index mismatch ∆n of about +8×10-5. The emitted beam is characterized using both M² measurements and time traces to study the changeover of a stable temporal behavior to an unstable one.

Characterization of two ultrashort laser pulses using interferometric imaging of self-diffraction

Christoph Leithold, Jan Reislöhner, Holger Gies, and Adrian Pfeiffer

Doc ID: 307026 Received 12 Sep 2017; Accepted 16 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: Non-collinear pulse characterization methods can be applied to over-octave spanning waveforms, but geometrical effects in the nonlinear medium like beam smearing and critical sensitivity to beam alignment hinder their accurate application. Here, a method is introduced for the temporal and spatial characterization of two pulses by interferometric, spectrally resolved imaging of self-diffraction. Geometrical effects are resolved by the method and therefore do not limit the accuracy. Two methods for quantitative pulse retrieval are presented. One method is analytical and very fast, the other method is iterative and more robust if applied to noisy data.

Effects of defocus and other quadratic errors on OTF

Kevin Liang and Miguel Alonso

Doc ID: 309409 Received 18 Oct 2017; Accepted 15 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: Even for the simplest nontrivial aberration, defocus, and for a circular pupil, there is no theoretical closed-form expression for the optical transfer function (OTF). By using a simple approximation for the error at the pupil, we provide a simple yet accurate approximation for the OTF of a defocused system. We then generalize this approach to generic quadratic aberrations, including astigmatism.

The Variable Stripe Length method: influence of stripe lengths choice on measured optical gain

Luis Cerdán

Doc ID: 310025 Received 27 Oct 2017; Accepted 14 Nov 2017; Posted 15 Nov 2017  View: PDF

Abstract: The Variable Stripe Length (VSL) method is a very popular tool to measure the optical gain in thin film active devices. However, along the last decade experimental and theoretical evidences have been reported that cast doubts upon its reliability and that seriously discourage its application. Continuing in the path of finding new arguments against its use, this letter soundly demonstrates that the particular choice of stripe lengths in the VSL measurements profoundly influences the optical gains retrieved by this method. Thus, a single set of VSL data may render gain values differing tens of cm-1. The observed gain variability is ascribed to a combination of unavoidable experimental noise and incorrect assumptions in the analytical treatment (small-signal approximation).

Widely tunable optical parametric oscillation in a Kerr microresonator

Noel Sayson, Karen Webb, Stephane Coen, Miro Erkintalo, and Stuart Murdoch

Doc ID: 308086 Received 27 Sep 2017; Accepted 13 Nov 2017; Posted 14 Nov 2017  View: PDF

Abstract: We report on the first experimental demonstration of widely-tunable parametric sideband generation in a Kerr microresonator. Specifically, by pumping a silica microsphere in the normal dispersion regime, we achieve the generation of phase-matched four-wave mixing sidebands at large frequency detunings from the pump. Thanks to the role of higher-order dispersion in enabling phase matching, small variations of the pump wavelength translate into very large and controllable changes in the wavelengths of the generated sidebands: we experimentally demonstrate over 720 nm of tunability using a low-power continuous-wave pump laser in the C-band. We also derive simple theoretical predictions for the phase-matched sideband frequencies, and discuss the predictions in light of thediscrete cavity resonance frequencies. Our experimentally measured sideband wavelengths are in very good agreement with theoretical predictions obtained from our simple phase matching analysis.

Nonlinearity-aware 200-Gbit/s discrete multi-tone transmission for C-band short-reach optical interconnects with a single packaged EML

Lu Zhang, Xuezhi Hong, Xiaodan Pang, Oskars Ozolins, Aleksejs Udalcovs, Richard Schatz, Changjian Guo, Junwei Zhang, FREDRIK NORDWALL, Klaus Engenhardt, Urban Westergren, Sergei Popov, GUNNAR JACOBSEN, shilin xiao, Weisheng Hu, and Jiajia Chen

Doc ID: 306205 Received 01 Sep 2017; Accepted 13 Nov 2017; Posted 15 Nov 2017  View: PDF

Abstract: We experimentally demonstrate the transmission of 200-Gbit/s discrete multi-tone (DMT) at soft-FEC limit in an intensity-modulation direct-detection system with a single C-band packaged distributed feedback laser and traveling-wave electro absorption modulator (DFB-TWEAM), digital-to-analog converter (DAC) and photodiode. The bits and power loaded DMT signal is transmitted over 1.6 km standard single mode fiber (SSMF) with a net rate of 166.7-Gbit/s, achieving an effective electrical spectrum efficiency of 4.93 bit/s/Hz. Meanwhile, net rates of 174.2-Gbit/s and 179.5-Gbit/s are also demonstrated over 0.8km SSMF and in optical back-to-back case, respectively. The feature of the packaged DFB-TWEAM is presented. The nonlinearity-aware digital signal processing algorithm for channel equalization is mathematically described, which improves the signal-to-noise ratio up to 4 dB.

Chirped-pulse-based broadband RF channelization implemented by mode-locked laser and dispersion

Wenhui Hao, Yitang Dai, FEIFEI YIN, Yue Zhou, Jianqiang Li, Jian Dai, Wangzhe Li, and Kun Xu

Doc ID: 307824 Received 25 Sep 2017; Accepted 13 Nov 2017; Posted 15 Nov 2017  View: PDF

Abstract: Based on mode-locked laser and dispersion, a wideband radio frequency (RF) channelized receiver that can easily support hundreds of channels is proposed. By mixing a long-duration chirped pulse train and its own delayed copy, an equivalent RF local oscillation (LO) is produced which can down-convert the modulated signal to zero-intermediate-frequency (IF). The LO frequency can be changed by simply setting the delay between the two paths. Channelized receiving of broadband RF signals can be realized by parallel delay line arrays. Meanwhile, the using of in-phase/quadrature (I/Q) demodulation avoids the extra optical or electrical filtering as well as image interference. A receiver with channel spacing of 100 MHz, covering spectrum from DC to 18.4 GHz is experimentally demonstrated. The performances including signal-to- noise ratio (SNR), frequency response, spurious-free dynamic range (SFDR) and image rejection are analyzed.

Multilayered analog optical differentiating device: performance analysis on structural parameters

Wenhui Wu, Wei Jiang, Jiang Yang, Shaoxiang Gong, and Yungui Ma

Doc ID: 307048 Received 13 Sep 2017; Accepted 13 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: Analogy optical devices with the function of mathematical computation have recently gained strong research interests due to the potential application as accelerating hardware in traditional electronic computers. The performance of these wavefront-processing devices is primarily decided by the accuracy of the engineered angular scattering spectra usually using artificial optical structures. In this paper, we address this issue through the performance analysis of an analog second-order optical differentiator made of dielectric (Si-SiO2) multilayer films that enable analytical discussions and also a combined design. The performance could be optimized according to the Fourier spectrum width of the incident light whose wavefront represents the input function. Based on this, we propose different optical differentiating devices that work for different wave input conditions. Rescaling of the Fourier spectrum intensity is suggested to enhance the fabrication and measurement error tolerance of the device. The minimum number of multilayers is also discussed in order to improve the practical feasibility. The current results are thought instrumental in guiding the design and implementation of analogy optical computation devices.

Experimental Generation of Linearly Chirped 350 GHz-band Pulses with beyond 60 GHz Bandwidth

Hangkai Zhang, Shiwei Wang, Shi Jia, Xianbin Yu, Xiaofeng Jin, Shilie Zheng, Hao Chi, and Xianmin Zhang

Doc ID: 306548 Received 07 Sep 2017; Accepted 13 Nov 2017; Posted 20 Nov 2017  View: PDF

Abstract: We present in this paper experimental generation of linear frequency modulated (LFM) THz pulses with large bandwidth by using an optical interferometer based photonic scheme and cutting-edge THz transceiver technology. The LFM pulses exhibiting a bandwidth in excess of 60 GHz centered at 350 GHz are successfully generated in the experiment, which represents the first demonstration of large time-bandwidth products (TBWP) in the THz region above 300 GHz, to the best of our knowledge. The achieved TBWP of up to 527 features a range resolution better than 1 cm and has great potential in many prospective applications such as high resolution radar sensing and imaging.

Tens-of-Hz narrow-linewidth laser based on Stimulated Brillouin and Rayleigh scattering

Shihong Huang, Tao Zhu, Guolu Yin, Tianyi Lan, Ligang Huang, Fuhui Li, Yongzhong Bai, Dingrong Qu, Xianbin Huang, and FENG QIU

Doc ID: 305751 Received 28 Aug 2017; Accepted 13 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: We proposed and demonstrated a linewidth compression method of laser based on stimulated Brillouin scattering (SBS) and Rayleigh backscattering structure (RBS). The relationship between the output SBS laser linewidth and the input pump linewidth was studied theoretically and experimentally. It is shown that the narrower linewidth of the pump laser leads to the narrower bandwidth of the SBS gain, and finally the bandwidth of the SBS will tend to its intrinsic value as the linewidth of pump laser narrower than 10 kHz, then the linewidth of SBS fiber ring laser would tend to 200 Hz. In order to further reduce its linewidth with low cost, RBS and a simple dual-cavity feedback structure were added, and finally ~75-Hz narrow-linewidth laser with a side-mode suppression ratio of 70 dB was obtained.

Homographically generated light-sheets for themicroscopy of large specimens

Craig Russell, Eric Rees, and Clemens Kaminski

Doc ID: 304060 Received 29 Sep 2017; Accepted 12 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: We compare the performance of linear and nonlinear methods for aligning the excitation and detection planes throughout large specimen volumes in digitally scanned light sheet microscopy. An effective non-linear method involves registering four corner extrema of the imaging volume using a projective transform. We show this improves on the light collection efficiency of a 3-point affine registration by an average of 42% over a typical specimen volume, but increasingly higher-order corrections provide more modest returns. The accuracy of illumination/detection registration methods are now very pertinent to biological research in view of current trends towards imaging large or expanded samples, at depth, with diffraction limited resolution.

Two-mode surface plasmon lasing in hexagonal arrays

Vasco Tenner, Michiel de Dood, and Martin van Exter

Doc ID: 297731 Received 25 Aug 2017; Accepted 12 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: We demonstrate surface-plasmon lasing in hexagonal metal hole arrays with a semiconductor gain medium. The device can be tuned between two laser modes, with distinct wavelengths, spatial distributions and polarization patterns by changing the size of the optically pumped area. One of the modes exhibits a six-fold polarization pattern, while the mode observed for larger pump spots has a rotationally symmetric polarization pattern. We explain the mode tuning by the differences of in-plane and radiative out-of-plane losses of the modes. The spatial and polarization properties of the modes are conveniently described by a sum of vectorial OAM beams with orbital, spin and total angular momentum j = l+s.

A self-tuning optical resonator

Joanna Zielinska and Morgan Mitchell

Doc ID: 309076 Received 13 Oct 2017; Accepted 10 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: We demonstrate a nonlinear optical resonator that tunes itself onto resonance with an input beam. In a monolithic Fabry-Perot cavity implemented in rubidium-doped periodically-poled potassium titanyl phosphate, an intensity-dependent refractive index produces line-pulling by multiple free-spectral ranges (FSRs). In this condition, the cavity passively maintains optical resonance in the face of FSR-scale excursions of the drive laser frequency: when one resonant operating-point becomes unstable, the resonator rapidly transitions to another resonant operating point. We demonstrate stable second-harmonic generation with no active feedback to laser or cavity. The self-tuning effect appears to be supported by a very strong, previously unreported optical nonlinearity.

Sub-Rayleigh Resolution Ghost Imaging by Spatial Low-Pass Filtering

Xi-Hao Chen, Fan-Hui Kong, Qiang Fu, Shao-Ying Meng, and Ling-An Wu

Doc ID: 307789 Received 25 Sep 2017; Accepted 09 Nov 2017; Posted 22 Nov 2017  View: PDF

Abstract: A sub-Rayleigh resolution ghost imaging (GI) experiment is performed via post-detection spatial low-pass filtering of the instantaneous intensity. A super-resolution reconstructed image has been achieved, in which the spatial resolution can exceed the Rayleigh diffraction limit by more than a factor of two. The resolution depends on the filter threshold, and the Rayleigh limit can be exceeded for a wide choice of threshold values. The setup is simple and easy to implement, which is an advantage for practical applications.

Perfect Broad-Band Invisibility in Isotropic Media with Gain and Loss

Farhang Loran and Ali Mostafazadeh

Doc ID: 305770 Received 28 Aug 2017; Accepted 06 Nov 2017; Posted 13 Nov 2017  View: PDF

Abstract: We offer a simple route to perfect omnidirectional invisibility in a spectral band of desired width which is based on the observation that in two dimensions a complex potential v(x,y) is invisible for incident plane waves with a wavenumber not exceeding a preassigned value α provided that its Fourier transform with respect to y, which we denote by $\tilde v(x,K_y)$, vanishes for $K_y ≤ 2α$. We can fulfil this condition for potentials modelling the permittivity profile of an optical slab. Such a slab is perfectly invisible for any transverse electric wave whose wavenumber is in the range [0,α]. Our results also apply to transverse magnetic waves propagating in a medium with a relative permittivity that is a smooth bounded function with a positive real part.

Effects of defocus on the transfer function of coherence scanning interferometry

Rong Su, MATTHEW THOMAS, Richard Leach, and Jeremy Coupland

Doc ID: 304940 Received 17 Aug 2017; Accepted 06 Nov 2017; Posted 07 Nov 2017  View: PDF

Abstract: Coherence scanning interferometry (CSI) offers three dimensional (3D) measurement of surface topography with high precision and accuracy. Defocus within the interferometric objective lens, however, is commonly present in CSI measurements, and reduces both the resolving power of the imaging system and the ability to measure tilted surfaces. This paper extends the linear theory of CSI to consider the effects of defocus on the 3D transfer function and the point spread function in an otherwise ideal CSI instrument. The results are compared with measurements of these functions in a real instrument. This work provides further evidence for the validity of the linear systems theory of CSI.

Intensity Noise Coupling in Soliton Fiber Oscillators

chenchen wan, Thomas Schibli, Peng Li, Carlo Bevilacqua, Axel Ruehl, and Ingmar Hartl

Doc ID: 301071 Received 01 Sep 2017; Accepted 24 Oct 2017; Posted 16 Nov 2017  View: PDF

Abstract: We present an experimental and numerical study on the spectrally resolved pump-to-output intensity noise coupling in soliton fiber oscillators. In our study we observe a strong pump noise coupling to the Kelly sidebands while the coupling to the soliton pulse is damped. This behavior is observed in Erbium-doped as well as Holmium-doped fiber oscillators and confirmed by numerical modeling. It can be seen as a general feature of laser oscillators where soliton pulse formation is dominant. We show that spectral blocking of the Kelly-sidebands outside the laser cavity can improve the intensity noise performance of the laser dramatically

An inclined emitting slotted single mode laser with 1.7 degree vertical divergence angle for PIC applications

Yejin Zhang, Yanmei Su, Yu Bi, Jiaoqing Pan, Hongyan Yu, yang zhang, Jie Sun, xinyan sun, and Ming Chong

Doc ID: 306547 Received 06 Sep 2017; Accepted 11 Oct 2017; Posted 30 Nov 2017  View: PDF

Abstract: In this letter, a new type of single mode slotted laser used for on-chip light source in photonic integrated circuits is proposed. An inclined light beam with a low vertical divergence angle can be directly coupled into the surface grating of the silicon to form an integrated light source. Experimentally, an III-V laser with a 54.6 degree inclined angle and a vertical divergence angle of 1.7 degree is achieved by introducing a kind of specially distributed micro-structure. The side mode suppression ratio is better than 45 dB and the continuous wave output power reaches 6.5 mW at room temperature. We report the inclined emitting micro-structured single mode laser with a low divergence angle for the first time.

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