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Accepted papers to appear in an upcoming issue

OSA now posts prepublication articles as soon as they are accepted and cleared for production. See the FAQ for additional information.

Rotating optical field due to residual phase gradients in optical null interference

Dinesh Naik, Pradeep Tagavula, and Nirmal Viswanathan

Doc ID: 250990 Received 30 Sep 2015; Accepted 25 Nov 2015; Posted 25 Nov 2015  View: PDF

Abstract: A scheme to sense the residual phase gradients in an optical interference of two out-of-phase Gaussian beams is proposed. In a Sagnac interferometer configured to provide a null output, an apparently negligible residual phase gradient unfolding an optical field rotation is presented.

Quantitative assessment of noise reduction with partial spatial coherence illumination in digital holographic microscopy

Frank Dubois, Jerome Dohet-Eraly, Catherine Yourassowsky, and Ahmed El Mallahi

Doc ID: 251639 Received 08 Oct 2015; Accepted 25 Nov 2015; Posted 25 Nov 2015  View: PDF

Abstract: Improving image quality in digital holographic microscopy is achievable by using partial spatial coherence illumination instead of fully coherent one. This Letter presents simple theoretical models to quantitatively assess the reduction of noise as a function of both the spatial coherence of the illumination and the defocus distance of the noise source. The first developed model states that the effect of the partial spatial coherence can be studied by discretizing the field of view in the plane of the noise-generating particles. The second model, following a continuous approach, corroborates the discrete model and extends it. Experimental results confirm theoretical expectations.

Full-color hologram using spatial multiplexing of dielectric metasurface

Wenyu Zhao, Bingyi Liu, Huan Jiang, Jie Song, Yanbo Pei, and Yongyuan Jiang

Doc ID: 252171 Received 19 Oct 2015; Accepted 24 Nov 2015; Posted 24 Nov 2015  View: PDF

Abstract: In this paper, we demonstrate a full-color hologram using spatial multiplexing of dielectric metasurface for three primary colors, capable of reconstructing arbitrary RGB images. The discrete phase maps for the red, green, and blue components of the target image are extracted through a classical Gerchberg–Saxton algorithm and reside in the corresponding sub-cells of each pixel. Silicon nanobars supporting narrow spectral response at the wavelengths of the three primary colors are employed as the basic meta-atoms to imprint the Pancharatnam-Berry phase while maintaining minimum crosstalk between different colors. The reconstructed holographic image agrees well with the target image making it promising for colorful display.

Development of integrated mode reformatting components for diffraction-limited spectroscopy

David MacLachlan, Robert Harris, Debaditya Choudhury, Richard Simmonds, Patrick Salter, Martin Booth, Jeremy Allington-Smith, and Robert Thomson

Doc ID: 250460 Received 29 Sep 2015; Accepted 23 Nov 2015; Posted 24 Nov 2015  View: PDF

Abstract: We present the results of our work on developing fully integrated devices (photonic dicers) for reformatting multimode light to a diffraction limited pseudo-slit. These devices can be used to couple a seeing-limited telescope point-spread-function to a spectrograph operating at the diffraction limit, thus enabling compact, high-resolution spectrographs that are free of modal-noise.

Frequency-resolved Raman for Transient Thermal Probing and Thermal Diffusivity Measurement

Xinwei Wang, Tianyu Wang, Shen Xu, David Hurley, and Yanan Yue

Doc ID: 251247 Received 01 Oct 2015; Accepted 23 Nov 2015; Posted 24 Nov 2015  View: PDF

Abstract: A new transient Raman thermal probing technique: frequency-resolved Raman (FR-Raman) is developed for probing the transient thermal response of materials and measuring their thermal diffusivity. The FR-Raman uses an amplitude modulated square-wave laser for simultaneous material heating and Raman excitation. The evolution profile of Raman properties: intensity, Raman wavenumber, and emission, against frequency are reconstructed and used for fitting to determine the thermal diffusivity. A microscale Si cantilever is used to investigate the capacity of this new technique. The thermal diffusivity is determined as 9.57×10^(-5) m^2/s, 11.00×10^(-5) m^2/s and 9.02×10^(-5) m^2/s, agreeing well with literature values. The FR-Raman provides a novel way for transient thermal probing with very high temporal resolution and μm-scale spatial resolution.

Mid-infrared photodetectors operating over an extended wavelength range up to 90 K

A. G. Unil Perera, Yanfeng Lao, Lian He Li, Suraj Khanna, Edmund Linfield, Y. H. Zhang, and T. M. Wang

Doc ID: 251304 Received 05 Oct 2015; Accepted 23 Nov 2015; Posted 24 Nov 2015  View: PDF

Abstract: We report a threshold extension, from the designed value of 3.1 μm to 8.9 μm in a p-type heterostructure photodetector . This is associated with the use of a graded barrier and barrier offset, which leads to hot carrier interactions. Experiments show that use of long-pass filters tunes the energies of incident photons, giving rise to the change in response threshold. This study demonstrates an alternative approach to achieve tuning photodetector response without the need to adjust the photodetector’s characteristic energy which is determined by the band structure.

Localized surface plasmon-enhanced light emission using Pt nanorings in deep UV-emitting AlGaN quantum wells

Tae-Geun Kim, Hee Woong Shin, and Kyungrock son

Doc ID: 249805 Received 14 Oct 2015; Accepted 21 Nov 2015; Posted 23 Nov 2015  View: PDF

Abstract: We report the enhancement of deep ultraviolet (DUV) emissions from AlGaN-based quantum wells (QWs) using energy-matched localized surface plasmons (LSPs) in Pt nanoring arrays. The peak resonances of extinction spectra were shifted to the red spectral region as the nanoring diameters increased, and the Pt nanorings with a diameter of 325 nm exhibited strong photoluminescence (PL) resonance at 279 nm. The emission enhancement ratio was calculated to be 304% in peak PL intensity when compared to that of the bare AlGaN QWs, which is attributed to the strung coupling of QWs with SPs from the Pt nanorings.

Variable wavefront tuning with a SLM for tailored femtosecond fiber Bragg grating inscription

Christian Voigtländer, Ria Krämer, Thorsten A. Goebel, Daniel Richter, and Stefan Nolte

Doc ID: 250578 Received 23 Sep 2015; Accepted 21 Nov 2015; Posted 23 Nov 2015  View: PDF

Abstract: We report on the inscription of fiber Bragg gratings using femtosecond laser pulses and the phase mask technique. The wavefront of the inscription laser is variably tuned with a spatial light modulator. By applying Fresnel lenses with different focal lengths, the period of the fiber Bragg gratings could be shifted. A linear change of the grating period for a FBG inscribed with a 3rd order deformed wavefront and a quadratic period behavior for a 4th order wavefront could be verified experimentally for the first time.

Simultaneous Polarization Mirau Interferometer Based on Pixelated Polarization Camera

Rongguang Liang and daodang wang

Doc ID: 252035 Received 15 Oct 2015; Accepted 21 Nov 2015; Posted 23 Nov 2015  View: PDF

Abstract: We propose a polarization Mirau interferometer using the pixelated polarization camera to acquire the four phase-shifted interferograms simultaneously, by which motionless phase shift can be realized. A wire grid polarizer is employed as the polarized beam splitter to realize the adjustable fringe contrast. Due to the limited contrast ratio of split orthogonally-polarized beams with wire grid polarizer, the corresponding calibration method by superposition of exchanged transmitted and reflected beams is proposed to obtain the uniform fringe contrast in four phase-shifted interferograms. The accuracy of the proposed system is demonstrated experimentally, and the precision better than 1/500 wavelength is achieved with the developed system. The proposed system provides a feasible way to realize the instantaneous measurement with minimization of environmental disturbance and also for the field measurement.

Telecentric suppression of diffuse light in imaging of highly anisotropic scattering media

Young Kim, Michelle Visbal Onufrak, and Raymond Konger

Doc ID: 254317 Received 20 Nov 2015; Accepted 21 Nov 2015; Posted 25 Nov 2015  View: PDF

Abstract: Telecentric lens, which are originally used in the machine vision industry, have often been utilized in biomedical imaging systems, due to the commonly known properties, such as large transverse field of view, constant magnification, and long working distance. However, its potential advantages in optical imaging of biological tissue, which is highly diffusive, have not been fully explored. We revisit that using a telecentric lens system can bring an alternative yet simple method for reducing unwanted scattering or diffuse light in biological tissue, owing to its highly anisotropic scattering properties. Using biological tissue and tissue phantoms, we demonstrate advantages attributed to the use of telecentric lens in tissue imaging, compared with imaging using conventional non-telecentric optics. Directional or angular gating (or filtering) using a telecentric lens is beneficial for removing a portion of diffuse light in highly anisotropic scattering media with high values of the scattering anisotropy factor. We envision that telecentric lens could be potentially incorporated into an instrument of modest design and cost, increasing rapid practical adoption.

Broadband active tuning of unidirectional scattering from nanoantenna using combined radially and azimuthally polarized beams

Zheng Xi, H. Urbach, Aurèle Adam, and Lei Wei

Doc ID: 252276 Received 20 Oct 2015; Accepted 20 Nov 2015; Posted 24 Nov 2015  View: PDF

Abstract: We propose an approach to actively tune the scattering pattern of a Mie-type spherical antenna. The scheme is based on separate control over the induced electric dipole and induced magnetic dipole using two coherent focused beams of radial polarization and azimuthal polarization respectively. By carefully tuning the amplitude and phase relation of the two beams, a broadband unidirectional scattering can be achieved, even at the wavelength where the antenna scatters most efficiently. By moving the focus of one beam, a drastic switch of the unidirectional scattering can be observed. Such scheme enables the design of ultra-compact optical switches and directional couplers based on nanoantennas.

Time-resolved shadowgraphs of transient plasma induced by spatiotemporally focused femtosecond laser pulses in fused silica glass

Ya Cheng, Zhaohui Wang, Bin Zeng, Guihua Li, Hongqiang Xie, Wei Chu, Fei He, Yang Liao, Weiwei Liu, and Hui Gao

Doc ID: 252737 Received 28 Oct 2015; Accepted 20 Nov 2015; Posted 20 Nov 2015  View: PDF

Abstract: We report on experimental observations of formation and evolution of transient plasma produced in fused silica glass with spatiotemporally focused (STF) femtosecond laser pulses using a pump-probe shadow imaging technique. Surprisingly, the observation shows that the track of the plasma is significantly curved, which is attributed to an asymmetric density distribution of the transient plasma produced in the focal volume caused by the pulse front tilt of the STF laser field.

Core-pumped single-frequency fiber amplifier with an output power of 158 W

Thomas Theeg, Christoph Ottenhues, Hakan Sayinc, Joerg Neumann, and Dietmar Kracht

Doc ID: 249900 Received 11 Sep 2015; Accepted 20 Nov 2015; Posted 20 Nov 2015  View: PDF

Abstract: Single-frequency laser sources at a wavelength of 1 µm are typically scaled in power with Ytterbium-doped double-clad fiber amplifiers. The main limitations are stimulated Brillouin scattering, transversal mode instabilities and from the technical point of view the degree of fiber integration for a rugged setup. Addressing these limitations, we propose an alternative high-power single-frequency amplifier concept based on core-pumping. A nonplanar ring-oscillator with 2 W of output power at 1 kHz spectral linewidth was scaled by an fiber amplifier up to a power of 158 W without any indication of stimulated Brillouin scattering – using a standard Ytterbium-doped single-mode fiber with a mode field area of only ~100µm². A short active fiber length and a strong temperature gradient along the gain fiber yield to efficient suppression of stimulated Brillouin scattering. For deeper understanding of the Brillouin scattering mitigation mechanism we studied the Brillouin gain spectra with a Fabry Pérot interferometer at different output power levels of the fiber amplifier. © 2015 Optical Society of America

Rotation of millimeter-size objects using ordinary light.

Olivier Emile and janine emile

Doc ID: 250415 Received 21 Sep 2015; Accepted 20 Nov 2015; Posted 20 Nov 2015  View: PDF

Abstract: The ability to optically rotate bodies offers new degrees of control of micro-objects with applications in various domains including micro-electromechanical-systems (MEMS), biomanipulations or optofluidics. Here we demonstrate the optically induced rotation of simple asymmetric two-dimensional objects using plane waves originating either from ordinary laser sources or from black body radiation. The objects are floating on an air/water interface. We observe a steady state rotation depending on the light intensity and on the asymmetry of the object. We interpret this rotation in terms of light diffraction by the edges of the object. Such systems could be easily implemented in optofluidic devices to induce liquid flow without the need for special light sources.

High Spectral Density Transmission Emulation Using ASE Noise as a Substitute for Nyquist-Spaced Channels

Daniel Elson, Lidia Galdino, Robert Maher, Robert Killey, Benn Thomsen, and Polina Bayvel

Doc ID: 251121 Received 15 Oct 2015; Accepted 20 Nov 2015; Posted 20 Nov 2015  View: PDF

Abstract: We demonstrate the use of spectrally shaped amplified spontaneous emission (SS-ASE) noise for wideband channel loading in the investigation of nonlinear transmission limits in WDM transmission experiments using Nyquist-spaced channels. The validity of this approach is explored through statistical analysis and experimental transmission of Nyquist-spaced 10 GBaud PDM-QPSK and PDM-16QAM channels, co-propagated with SS-ASE over single mode fiber. It is shown that that this technique, which is simpler to implement, than a fully modulated comb of channels, is valid for distances exceeding 240 km for PDM-16QAM with dispersion of 16 ps/nm/km², yields a good agreement with theory and provides a conservative measure of system performance.

Strong coupling of hybrid and plasmonic Resonaces in liquid core plasmonic micro bubble cavities

Liying Liu, Lei Xu, Qijing Lu, Ming Li, Xiang Wu, Liao Jie, and Liu Sheng

Doc ID: 252137 Received 19 Oct 2015; Accepted 20 Nov 2015; Posted 20 Nov 2015  View: PDF

Abstract: Thin wall plasmonic micro-bubble resonator, which is a high Q optofluidic silica bubble cavity with a thin Ag film on the inside wall of the bubble, is proposed and fabricated to manipulate coupling between various types of resonant modes by changing its wall thickness and refractive index of the liquid in the core. Coupling of high Q whispering gallery mode/plasmonic resonant mode forms hybrid mode, the hybrid mode can again strongly couple with another interior plasmonic resonant mode in the bubble cavity to achieve tunable high Q plasmonic resonance that can be feasibly accessed by standard tapered fiber coupling. The novel cavity structure therefore provides a unique yet general platform to study plasmonic/photonic, hybrid/plasmonic and plasmonic/plasmonic coupling.

A novel broadband and wide range feedback tuning scheme for PLL stabilization of tunable optoelectronic oscillators

Xingyuan Xu, Jian Dai, Yitang Dai, Feifei Yin, Yue Zhou, Jianqiang Li, Jie Yin, Qunyang Wang, and Kun Xu

Doc ID: 252144 Received 16 Oct 2015; Accepted 20 Nov 2015; Posted 20 Nov 2015  View: PDF

Abstract: In this letter, we proposed and experimentally demonstrated a novel broadband and wide range feedback tuning scheme for phase-locked loop (PLL) stabilization of tunable optoelectronic oscillators (OEO). The proposed scheme was realized in a simple and feasible way based on dual-parallel Mach-Zehnder modulator (DPMZM) and optical bandpass filter (OBPF). The wide RF phase shift range and broadband performance of the proposed scheme were demonstrated theoretically and experimentally, which ensured OEO’s wide operating temperature range and tunability in PLL stabilization. As a result, PLL stabilization for OEO was achieved at different oscillating frequencies and the long-term stability was greatly improved without any thermal control. The measured overlapping Allan Deviation of PLL-locked OEO reached lower than 〖10〗^(-10) after 1000-s averaging time, which was four orders of magnitude better than the free-running OEO. The phase noise performance was also improved at low offset frequencies and remained the same at high offset frequencies.

Solid electrically tunable dual-focus lens using freeform surfaces and MEMS actuator

Guangya Zhou, Yongchao Zou, Wei Zhang, and Fook Siong Chau

Doc ID: 252222 Received 20 Oct 2015; Accepted 19 Nov 2015; Posted 20 Nov 2015  View: PDF

Abstract: In this letter, we present a miniature solid tunable dual-focus lens, which is designed using freeform optical surfaces and driven by one MEMS (micro-electro-mechanical-systems) rotary actuator. Such a lens consists of two optical elements, each having a flat surface and one freeform surface optimized by ray tracing technology. By changing the relative rotation angle of the two lens elements, the lens configuration can form double foci with corresponding focal lengths varied simultaneously, resulting in a tunable dual-focus effect. Results show that one of the focal length is tuned from about 30mm to 20 mm while the other one is varied from about 30 mm to 60 mm, with a maximum rotation angle of about 8.2 degrees.

Hard X-ray spectroscopy and imaging by a reflection zone plate in the presence of astigmatism

Christoph Braig, Heike Löchel, Alexander Firsov, Maria Brzhezinskaya, Aljosa Hafner, Jens Rehanek, Michael Wojcik, Albert Macrander, Lahsen Assoufid, and Alexei Erko

Doc ID: 252232 Received 19 Oct 2015; Accepted 19 Nov 2015; Posted 20 Nov 2015  View: PDF

Abstract: The feasibility of an off-axis X-ray reflection zone plate to perform wavelength-dispersive spectroscopy, on-axis point focusing and two-dimensional (2D) imaging is demonstrated by means of one and the same diffractive optical element (DOE) at a synchrotron radiation facility. The resolving power varies between 3 × 10¹ and 4 × 10² in the range from 7.6 keV to 9.0 keV, with its maximum at the design energy of 8.3 keV. This result is verified using an adjustable entrance slit, by which horizontal (H) and vertical (V) focusing to 0.85 mm (H) and 1.29 mm (V) is obtained near the sagittal focal plane of the astigmatic configuration. An angular and axial scan proves an accessible field of view of at least 0.6 × 0.8 arcmin² and a focal depth of ± 0.86 mm. Supported by the grating efficiency around 17.6% and a very short pulse elongation, future precision X-ray fluorescence and absorption studies of transition metals at their K-edge on an ultrashort timescale could benefit from our findings.

Gigabit Ethernet Signal Transmission Using Asynchronous OCDMA

Yechi Ma, Mable Fok, Bhavin Shastri, Ben Wu, and Paul Prucnal

Doc ID: 250006 Received 23 Sep 2015; Accepted 19 Nov 2015; Posted 20 Nov 2015  View: PDF

Abstract: We propose and experimentally demonstrate a novel architecture for interfacing and transmitting Gigabit Ethernet (GbE) signal using asynchronous incoherent optical code division multiple access (OCDMA). This is the first such asynchronous incoherent OCDMA system carrying GbE data being demonstrated to be working among multi-users where each user is operating with an independent clock/data rate and granted with random access to the network. Three major components, GbE interface, OCDMA transmitter and OCDMA receiver are discussed in detail. The performance of the system is studied and characterized through measuring eye diagrams, bit-error rate and packet loss rate in real time file transfer. Our work also addresses the near-far problem and realizes asynchronous transmission and detection of signal.

AuAg bimetallic non-alloyed nanoparticles on a periodically nanostructured GaAs substrate for high-efficiency light-trapping effect

Soo Kyung Lee, CheeLeong Tan, Gun Wu Ju, JaeHong Song, Chan il Yeo, and Yong-Tak Lee

Doc ID: 252255 Received 22 Oct 2015; Accepted 19 Nov 2015; Posted 19 Nov 2015  View: PDF

Abstract: We present a light trapping structure consisting of AuAg bimetallic non-alloyed nanoparticles (BNNPs) on cone-shaped GaAs subwavelength structures (SWSs), combining the advantages of plasmonic structures and SWSs, for GaAs based solar cell applications. To obtain efficient light trapping effects for solar cell applications, the optical properties’ dependence on the size and composition of the Ag and Au metal nanoparticles was systematically investigated. Cone-shaped GaAs SWSs with AuAg BNNPs formed from a Au film of 12 nm and a Ag film of 10 nm exhibited the extremely low average reflectance (Ravg) of 2.43% and the solar-weighted reflectance (SWR) of 2.38%, compared to that of a bare GaAs substrate (Ravg, 37.50%; SWR, 36.72%) in the wavelength range from 300 to 870 nm.

640 Gbit/s RZ-to-NRZ format conversion based on optical linear spectral phase filtering

Reza Maram, Deming Kong, Michael Galili, Leif Oxenlowe, and Jose Azana

Doc ID: 235109 Received 22 Oct 2015; Accepted 19 Nov 2015; Posted 23 Nov 2015  View: PDF

Abstract: We propose a novel approach for all-optical return-to-zero (RZ)-to-non-RZ (NRZ) telecommunication data format conversion based on linear spectral phase manipulation of an RZ data signal. The operation principle is numerically analyzed and experimentally validated through successful format conversion of a 640 Gbit/s coherent RZ signal into the equivalent NRZ time-domain data using a simple phase filter implemented by a commercial optical wave-shaper.

Microwave photonic integrator based on a multichannel fiber Bragg grating

Jianping Yao and Jiejun Zhang

Doc ID: 250706 Received 23 Sep 2015; Accepted 19 Nov 2015; Posted 24 Nov 2015  View: PDF

Abstract: We propose and experimentally demonstrate a microwave photonic integrator based on a multichannel fiber Bragg grating (FBG) working in conjunction with a dispersion compensating fiber (DCF) to provide a step group delay response, with no in-channel dispersion-related distortion. The multichannel FBG is designed based on the spectral Talbot effect, which provides a large group delay dispersion (GDD) within each channel. A step group delay response can then be achieved by cascading the multichannel FBG with a DCF having a GDD opposite to the in-channel GDD. An optical comb with each comb line located at the center of each channel of the FBG is modulated by a microwave signal to be integrated. At the output of the DCF, multiple time-delayed replicas of the optical signal with equal time delay spacing are obtained which are detected and summed at a photodetector (PD). The entire operation is equivalent to an integration of the input microwave signal. The proposed integrator is experimentally evaluated. For a multichannel FBG with an in-channel GDD of 730 ps/nm and a DCF with an opposite GDD, an integrator with a bandwidth of 2.9 GHz and an integration time of 7 ns is demonstrated.

Suppressing Rayleigh backscatter and code noise from all-fiber digital interferometers

Silvie Ngo, Daniel Shaddock, Terry McRae, Timothy Lam, Jong Chow, and Malcolm Gray

Doc ID: 251596 Received 08 Oct 2015; Accepted 19 Nov 2015; Posted 25 Nov 2015  View: PDF

Abstract: We configure an all-fiber digital interferometer to eliminate both code noise and Rayleigh backscatter noise from bidirectional measurements. We utilize a sawtooth phase ramp to upconvert code noise beyond our signal bandwidth, demonstrating an in-band noise reduction of approximately two orders of magnitude. In addition, we demonstrate, for the first time, the use of relative code delays within a digital interferometer system to eliminate Rayleigh backscatter noise, resulting in a noise reduction of a factor of 50. Finally, we identify double Rayleigh backscatter noise as our limiting noise source and suggest two methods to minimize this noise source.

Spatio-temporal second-order quantum correlations of surface plasmon polaritons

Aurelien Drezet, martin B berthel, and Serge Huant

Doc ID: 250552 Received 24 Sep 2015; Accepted 18 Nov 2015; Posted 19 Nov 2015  View: PDF

Abstract: We present an experimental methodology to observe spatio-temporal second-order quantum coherence of surface plasmon polaritons which are emitted by nitrogen vacancy color centers attached at the apex of an optical tip. The approach relies on leakage radiation microscopy in the Fourier space and we use this approach to test wave-particle duality for surface plasmon polaritons.

Broadband high power mid-IR femtosecond pulse generation from an ytterbium-doped fiber laser pumped optical parametric amplifier

Chengzhi Hu, Tao Chen, Peipei Jiang, Bo Wu, jianjia su, and Yonghang Shen

Doc ID: 252299 Received 20 Oct 2015; Accepted 18 Nov 2015; Posted 18 Nov 2015  View: PDF

Abstract: We report a high power periodically poled MgO-doped lithium niobate (MgO:PPLN) based femtosecond optical parametric amplifier (OPA), featuring a spectral seamless broadband mid-IR output. By modifying the initial chirp and spectrum of the mode-locked seed laser, a final output power of 14 W with sub 200 fs pulse duration was achieved from the Yb fiber laser after power amplification and compression. When the OPA was seeded with a broadband amplified spontaneous emission(ASE) source, a damage-limited 0.6 W broadband mid-infrared radiation was experimentally obtained under the pump power of 10.15 W at 82MHz repetition rate, corresponding to an overall OPA conversion efficiency of 32.7%. The 3-dB bandwidth of the mid-IR idler was 291.9 nm, centering at 3.34mm.

Radial Smoothing for improving laser-beam irradiance uniformity

Bin Zhang, pengcheng Hou, and Zheqiang Zhong

Doc ID: 252945 Received 30 Oct 2015; Accepted 17 Nov 2015; Posted 18 Nov 2015  View: PDF

Abstract: Laser-beam irradiation uniformity is a key issue in inertial confinement fusion research. We propose a radial smoothing approach in which the speckle in focal plane is smoothed by the radial redistribution through the fast focal zooming. This focal zooming is generated by introducing the periodical spherical wavefront modulation to the laser beam based on an optical Kerr medium and its pump laser with the temporal profile of a Gaussian pulse train. The utilization of radial smoothing significantly improves the laser-beam uniformity without obvious impact on the performance of the high-power laser system.

3D laser-written silica glass step-index high-contrast waveguides for the 3.5 μm mid-infrared range

Airán Ródenas, Javier Martinez, Toney Fernandez, Javier Vazquez de Aldana, Robert Thomson, Magdalena Aguiló, Ajoy Kumar Kar, Javier Solis, and Francesc Diaz

Doc ID: 250479 Received 21 Sep 2015; Accepted 17 Nov 2015; Posted 19 Nov 2015  View: PDF

Abstract: We report on the direct laser fabrication of step-index waveguides in fused silica substrates for operation in the 3.5 µm mid-infrared wavelength range. We demonstrate core-cladding index contrasts of 0.7%, enabling bends, low-loss coupling to commercial fluoride fibers, and propagation losses of 1.3 (6.5) dB/cm at 3.39 (3.68) µm, close to the intrinsic losses of the glass. We also report on the existence of three different laser modified SiO2 glass volumes, their different micro-Raman spectra, and their different temperature dependent populations of color centers, tentatively clarifying the SiO2 lattice changes which are related to the large index changes.

Superresolved swept wavelength interferometry using frequency estimation methods

Martha Bodine and Robert McLeod

Doc ID: 250908 Received 05 Oct 2015; Accepted 17 Nov 2015; Posted 20 Nov 2015  View: PDF

Abstract: The high signal-to-noise ratios typical of swept wavelength interferometry (SWI) enable distance measurements to be superresolved with 2σ uncertainties as low as 1E-4 to 1E-5 of Fourier transform-limited resolution. We compare three methods of superresolving SWI distance measurements: Local Linear Regression (LLR), Estimation of Signal Parameters via Rotational Invariance Techniques (ESPRIT), and Nonlinear Least Squares (NLS). We find that the superresolution method limits both measurement precision and minimum superresolvable distance. Measurement uncertainty is determined by both the superresolution method and the SWI hardware, while SWI hardware alone limits the maximum superresolvable distance. For very short distances, between 2 and 20 times the SWI system’s Fourier transform-limited resolution, NLS provides unbiased estimates with the least uncertainty. At longer distances, LLR provides the fastest unbiased estimates. LLR and NLS are more noise tolerant than ESPRIT and are found to operate close to the Cramér-Rao bound. With sufficient SNR, they provide 1σ measurement precision of 1E-8 of the transform limit.

Polarization Encoded Chirped Pulse Amplification in Ti:sapphire – a way towards few cycle PW lasers

Mikhail Kalashnikov, Huabao Cao, Vladimir Chvykov, and Karoly Osvay

Doc ID: 251029 Received 29 Sep 2015; Accepted 17 Nov 2015; Posted 20 Nov 2015  View: PDF

Abstract: The bandwidth of Ti:Sa laser amplifiers can be greatly broadened with shaping the spectral gain via engineering the spectral polarization of amplified pulses and using both π and σ cross-sections. In a proof-of-principle experiment, an amplification bandwidth exceeding 85 nm at a gain of 200 was demonstrated. The accompanying computer modeling revealed that a polarization encoded chirped pulse amplification scheme (PE-CPA) can be scaled to higher energies and thus can produce multi-joule pulses with bandwidth close to 200nm, making few cycle PW Ti:Sa systems feasible.

Faraday rotation in Bilayer Graphene-based integrated microcavity

xia da and Xiaohong Yan

Doc ID: 252732 Received 28 Oct 2015; Accepted 17 Nov 2015; Posted 20 Nov 2015  View: PDF

Abstract: AB-stacked bilayer graphene has rich ground states with various broken symmetries, allowing the existence of magnetooptical effects even in the absence of external magnetic field. Here we report controllable Faraday rotation of bilayer graphene induced by electrostatically gate voltage, whose value is 10 times smaller than the case of single layer graphene with magnetic field. A proposed bilayer graphene-based microcavity configuration enables the enhanced Faraday rotation angle due to the large localized electromagnetic field. Our results offer unique opportunities to apply bilayer graphene for magnetooptical devices.

Precise multi-emitter localization method for a fast super-resolution imaging

Yuto Ashida and Masahito Ueda

Doc ID: 250252 Received 17 Sep 2015; Accepted 17 Nov 2015; Posted 25 Nov 2015  View: PDF

Abstract: We present a method that can simultaneously locate positions of overlapped multi-emitters at the theoretical-limit precision. We derive a set of simple equations whose solution gives the maximum likelihood estimator of multi-emitter positions. We compare the performance of our simultaneous localization analysis with the conventional single-molecule analysis for simulated images and show that our method can improve the time-resolution of superresolution microscopy an order of magnitude. In particular, we derive the information-theoretical bound on time resolution of localization-based superresolution microscopy and demonstrate that the bound can be closely attained by our analysis.

Generation of five phase-locked harmonics by implementing a divide-by-three optical frequency divider

Masayuki Katsuragawa, Chiaki Ohae, Nurul Suahimi, Gavara Trivikramarao, Ken'ichi Nakagawa, and Feng Hong

Doc ID: 252662 Received 26 Oct 2015; Accepted 17 Nov 2015; Posted 17 Nov 2015  View: PDF

Abstract: We report the generation of five phase-locked harmonics, f_1: 2403 nm, f_2: 1201 nm, f_3: 801 nm, f_4: 600 nm, and f_5: 480 nm with an exact frequency ratio of 1 : 2 : 3 : 4 : 5 by implementing a divide-by-three optical-frequency divider in the high harmonic generation process. All five harmonics are generated coaxially with high phase coherence in time and space, which are applicable for various practical uses.

Performance of a q-plate tunable retarder in reflection for the switchable generation of both first and second order vector beams

Maria del Mar Sanchez-Lopez, Jeffrey Davis, Nobuyuki Hashimoto, Ignacio Moreno, Enrique Hurtado, Katherine Badham, Ayano Tanabe, and Sam Delaney

Doc ID: 250783 Received 28 Sep 2015; Accepted 17 Nov 2015; Posted 18 Nov 2015  View: PDF

Abstract: We examine the performance of a tunable liquid crystal q-plate in a reflective geometry. We find that when the device is tuned to a half-wave retardance, it operates as a q-plate with twice the value (2q) by adding a quarter-wave retarder between the mirror and the q-plate. However, when the device is tuned to a quarter-wave retardance, it acts as the original q-plate without the requirement of the retarder. Experimental results are shown. Combined with an input tunable polarization state generator, the system allows the switchable production of all states on both the first and second order Poincaré spheres. Jones matrix analysis proves the validity of the proposed reflective system to double the q value.

Efficient narrowband terahertz generation in cryogenically cooled periodically poled lithium niobate

Sergio Carbajo, Jan Schulte, Xiaojun Wu, Koustuban Ravi, Damian Schimpf, and Franz Kaertner

Doc ID: 251861 Received 14 Oct 2015; Accepted 17 Nov 2015; Posted 18 Nov 2015  View: PDF

Abstract: We present an efficiency scaling study of optical rectification in cryogenically cooled periodically poled lithium niobate for the generation of narrowband terahertz radiation using ultrashort pulses. The results show an efficiency and brilliance increase compared to previous schemes of up to two orders of magnitude by exploring the optimal pump pulse format at around 800 nm, and reveal saturation mechanisms limiting the conversion efficiency. We achieve >10¯³ energy conversion efficiencies, µJ-level energies, and bandwidths <20 GHz at ~0.5 THz, thereby showing unprecedented spectral brightness in the 0.1-1 THz range relevant to terahertz science and technology.

Resonant micro optic gyro using a short and high-finesse fiber ring resonator

Huilian Ma, Jianjie Zhang, Linglan Wang, Diqing Ying, Zhonghe Jin, and Ying Lu

Doc ID: 251953 Received 14 Oct 2015; Accepted 17 Nov 2015; Posted 18 Nov 2015  View: PDF

Abstract: A novel hybrid integrated scheme is proposed for a high-performance RMOG which requires a low-loss micro-ring resonator for mass production. A new record for the RMOGs is established experimentally with a short fiber ring resonator and an integrated signal detecting and processing circuit. The finesse of the short fiber ring resonator with a length of 60 cm and a diameter of 4.77 cm is as high as 202, and the theoretical sensitivity of the RMOG is better than 0.3 deg/h assuming the average optical intensity at the photodetector is 1 mW. The 60-cm long spliceless micro-ring resonator is experimentally proved to be sufficient for a tactical-grade RMOG. An angle random walk coefficient of 0.64 deg/√h and a typical bias stability below 9.6 deg/h for the integration time of 50 seconds are successfully demonstrated for operation times of 1600 seconds.

Ultra-high Quality Factor in a Metal-embedded Semiconductor Microdisk Cavity

Hiroyuki Kurosawa, Hidekazu Kumano, and Ikuo Suemune

Doc ID: 251895 Received 15 Oct 2015; Accepted 16 Nov 2015; Posted 16 Nov 2015  View: PDF

Abstract: We numerically and theoretically investigate electrodynamics of a metal-embedded semiconductor microdisk cavity. The electrodynamics of a cavity mode is discussed from the viewpoint of quantum mechanics, which clarifies the condition for high Q factor. Using numerical calculation, we optimize the cavity structure and show that the Q factor can be increased up to 1,700,000. Our study suggests that the metal-embedded cavity is a promising candidate for cavity quantum electrodynamics devices.

Radially polarized emission with 635 W of average power and 2.1 mJ of pulse energy generated by an ultrafast thin-disk multipass amplifier

André Loescher, Jan-Philipp Negel, Marwan Abdou Ahmed, and Thomas Graf

Doc ID: 251105 Received 30 Sep 2015; Accepted 15 Nov 2015; Posted 16 Nov 2015  View: PDF

Abstract: We report on a thin-disk multipass amplifier delivering radially polarized laser pulses with an average power of 635 W and 2.1 mJ of pulse energy. To the best of our knowledge this is the highest average output power and pulse energy reported so far for radially polarized ultrafast lasers. The amplifier is seeded by a TruMicro5050 with 115 W of average output power, 6.5 ps pulse duration, and a repetition rate of 300 kHz. A segmented half-waveplate was used for converting the linearly polarized beam into radial polarization in front of the amplifier. We present a scheme for direct amplification of such doughnut-shaped radially-polarized beams, the results obtained and a solution to compensate for the depolarizing phase shift introduced by the tilted mirrors in the amplifier.

Production of Dynamic Frozen Waves: Controlling shape, location (and speed) of diffraction-resistant beams

Marcos Gesualdi, Michel Zamboni-Rached, Tárcio Vieira, and Erasmo Recami

Doc ID: 250488 Received 22 Sep 2015; Accepted 15 Nov 2015; Posted 16 Nov 2015  View: PDF

Abstract: In recent times, we experimentally realized a quite efficient modeling of the shape of diffraction-resistant optical beams; thus generating for the first time the so-called Frozen Waves (FW), whose longitudinal intensity pattern can be arbitrarily chosen, within a prefixed space interval of the propagation axis. In this work, we extend our theory of FWs -which led to beams endowed with a static envelope- through a dynamic modeling of the FWs, whose shape is now allowed to evolve in time in a predetermined way. And we experimentally create such dynamic FWs in Optics, via a computational holographic technique and a spatial light modulator. Experimental results are here presented for two cases of dynamic FWs, one of the zeroth and the other of higher order, the last one being the most interesting, consisting in a cylindrical surface of light whose geometry changes in space and time.

Photothermal Speckle Modulation for Noncontact Materials Characterization

Alexander Stolyarov, Ryan Sullenberger, David Crompton, Thomas Jeys, Brian Saar, and William Herzog

Doc ID: 250911 Received 28 Sep 2015; Accepted 15 Nov 2015; Posted 16 Nov 2015  View: PDF

Abstract: We have developed a noncontact, photothermal materials characterization method based on visible-light speckle imaging. This technique is applied to remotely measure the infrared absorption spectra of materials and to discriminate materials based on their thermal conductivities. A wavelength-tunable (7.5-8.7-µm), intensity-modulated, quantum cascade pump laser and a continuous-wave 532-nm probe laser illuminate a sample surface such that the two laser spots overlap. Surface absorption of the intensity-modulated pump laser induces a time-varying thermoelastic surface deformation, resulting in a time-varying 532-nm scattering speckle field from the surface. The speckle modulation amplitude, derived from a series of visible camera images, is found to correlate with the amplitude of the surface motion. By tuning the pump laser’s wavelength over a molecular absorption feature, the amplitude spectrum of the speckle modulation is found to correlate to the IR absorption spectrum. As an example, we demonstrate this technique for spectroscopic identification of thin polymeric films. Furthermore, by adjusting the rate of modulation of the pump beam and measuring the associated modulation transfer to the visible speckle pattern, information about the thermal time constants of surface and sub-surface features can be revealed. Using this approach, we demonstrate the ability to distinguish between different materials (including metals, semiconductors, and insulators) based on differences in their thermal conductivities.

Numerical and experimental demonstration of a wavelength demultiplexer design by point-defect cavity coupled to tapered photonic crystal waveguide

Mirbek Turduev, Zeki Hayran, Muriel Botey, Ramon Herrero, Kestutis Staliunas, and Hamza Kurt

Doc ID: 250748 Received 25 Sep 2015; Accepted 14 Nov 2015; Posted 16 Nov 2015  View: PDF

Abstract: We propose and experimentally demonstrate a demultiplexer with point-defect resonators and a reflection feedback mechanism in a photonic crystal waveguide. A tapered photonic crystal waveguide has been chosen as the necessary reflector, which greatly enhances the drop efficiency. Due to the variation of the single mode waveguide width of the tapered waveguide, spatial alterations of the effective refractive index can be achieved. This phenomenon is used to slow down a propagating wave and stop it at a frequency dependent spatial position, which is then reflected back and coupled again to the drop channel via the resonator. High transmission efficiency to the drop-out channels is numerically predicted by calculations either in two- and three- dimensional model and analytically described by a coupled-mode theory. Moreover, an experimental realization in the microwave regime provides confirmation that the targeted wavelengths can be properly transmitted at the drop channels with low cross talk and relatively high efficiencies.

Type IIa Bragg grating based ultra-short DBR fiber laser with high temperature resistance

Bai-Ou Guan, Yang Ran, Feng Furong, Liang Yizhi, and Long Jin

Doc ID: 251004 Received 29 Sep 2015; Accepted 13 Nov 2015; Posted 16 Nov 2015  View: PDF

Abstract: An ultra-short distributed Bragg reflector fiber laser is fabricated by directly inscribing two type IIa gratings in Er-doped fiber. The abnormal spectral evolution characteristic of the type IIa grating in Er-doped fiber is discussed. The entire laser length, including the two type IIa gratings is only 13 mm. The laser can be stably operated at 600 OC, which provides potential applications in harsh temperature environments.

Ultrahigh-resolution optical coherence elastography

Andrea Curatolo, Martin Villiger, Dirk Lorenser, Philip Wijesinghe, Alexander Fritz, Brendan Kennedy, and David Sampson

Doc ID: 251312 Received 05 Oct 2015; Accepted 13 Nov 2015; Posted 13 Nov 2015  View: PDF

Abstract: Visualizing stiffness within the local tissue environment at the cellular and sub-cellular level promises to provide insight into the genesis and progression of disease. In this paper, we propose ultrahigh-resolution optical coherence elastography, and demonstrate three-dimensional imaging of local axial strain of tissues undergoing compressive loading. We combine optical coherence microscopy and phase-sensitive detection of local tissue displacement to produce strain elastograms with resolution (x,y,z) of 2×2×15 μm. We demonstrate this performance on freshly excised mouse aorta and reveal the mechanical heterogeneity of vascular smooth muscle cells and elastin sheets, otherwise unresolved in a typical, lower resolution optical coherence elastography system.

Simultaneous optical coherence tomography angiography and fluorescein angiography in rodents with normal retina and laser-induced choroidal neovascularization

wenzhong liu, Hao Li, Ronil Shah, Xiao Shu, Robert Linsenmeier, Amani Fawzi, and Hao Zhang

Doc ID: 248816 Received 27 Aug 2015; Accepted 13 Nov 2015; Posted 16 Nov 2015  View: PDF

Abstract: Fluorescein angiography (FA) is the current clinical imaging standard for vascular related retinal diseases such as macular degeneration and diabetic retinopathy. However, FA is considered invasive and can only provide two-dimensional imaging. In comparison, optical coherence tomography angiography (OCTA) is non-invasive and can generate three-dimensional imaging; investigations of OCTA already demonstrated great promise in retinal vascular imaging. Yet, to further develop and apply OCTA, strengths and weaknesses between OCTA and FA need to be thoroughly compared. To avoid complications in image registration, an ideal comparison requires co-registered and simultaneous imaging by both FA and OCTA. In this study, we developed a system with integrated laser-scanning ophthalmoscope FA (SLO-FA) and OCTA, and conducted simultaneous dual-modality retinal vascular imaging in rodents. In imaging healthy rodent eyes, OCTA can resolve retinal capillaries better than SLO-FA does, particularly deep capillaries. In imaging rodent eyes with laser-induced choroidal neovascularization (CNV), OCTA can identify CNV that eludes SLO-FA detection

Photoluminescence from voids created by femtosecond laser pulses inside cubic-BN

Saulius Juodkazis, Ricardas Buividas, Igor Aharonovich, Gediminas Seniutinas, Xue Wang, Ludovic Rapp, Andrei Rode, and Takashi Taniguchi

Doc ID: 252175 Received 19 Oct 2015; Accepted 12 Nov 2015; Posted 12 Nov 2015  View: PDF

Abstract: Photoluminescence (PL) from femtosecond laser modified regions inside cubic-boron nitride (c-BN) was measured under UV and visible light excitation. Bright PL at the red spectral range was observed, with a typical excited state lifetime of $\sim 4$~ns. Sharp emission lines are consistent with PL of intrinsic vibronic defects linked to the nitrogen vacancy formation (via Frenkel pair) observed earlier in high energy electron irradiated and ion-implanted c-BN. These, formerly known as the radiation centers, RC1, RC2, and RC3 have been identified at the locus of the voids formed by single fs-laser pulse. The method is promising to engineer color centers in c-BN for photonic applications.

Beam-Scanning for Rapid Coherent Raman Hyperspectral Imaging

Young Lee, Ian Ryu, Charles Camp Jr., Ying Jin, and Marcus Cicerone

Doc ID: 250909 Received 28 Sep 2015; Accepted 12 Nov 2015; Posted 13 Nov 2015  View: PDF

Abstract: Coherent Raman imaging requires high peak power laser pulses to maximize the nonlinear multiphoton signal generation, but accompanying photo-induced sample damage often poses a challenge to microscopic imaging studies. We demonstrate that beam-scanning by a 3.5-kHz resonant mirror in a broadband coherent anti-Stokes Raman scattering (BCARS) imaging system can reduce photo-induced damage without compromising the signal intensity. Additionally, beam-scanning enables slit-acquisition, in which spectra from a thin line of sample illumination are acquired in parallel during a single charge-coupled device (CCD) exposure. Reflective mirrors are employed in the beam-scanning assembly to minimize chromatic aberration and temporal dispersion. The combined approach of beam-scanning and slit-acquisition is compared with the sample-scanning mode in terms of spatial resolution, photo-induced damage, and imaging speed at the maximum laser power below the sample damage threshold. We show that the beam-scanning BCARS imaging method can reduce photodamage probability in biological cells and tissues, enabling faster imaging speed by using higher excitation laser power than could be achieved without the beam-scanning.

Ultra-broadband Ghost Imaging exploiting opto-electronic Amplified Spontaneous Emission and Two-Photon Detection

Sébastien Hartmann, Andreas Molitor, and Wolfgang Elsaesser

Doc ID: 249989 Received 14 Sep 2015; Accepted 11 Nov 2015; Posted 13 Nov 2015  View: PDF

Abstract: Ghost imaging (GI) is one of the recent fascinating and probably counterintuitive topics of quantum optics. Here, we realize an alternative classical GI experiment using spectrally ultra-broadband amplified spontaneous emission from an optoelectronic quantum dot based superluminescent diode source. This light source exhibits highly incoherent properties regarding both first and second order correlations with a 70 nm wide optical spectrum as well as thermal-like photon statistics. In a proof-of-principle experiment exploiting an ultrafast two-photon-absorption detection method, we demonstrate for the first time ghost image reconstruction handling the corresponding femtosecond correlation timescales. By introducing compact broadband light sources to GI, this work contributes towards practical application of GI.

Confocal microscopy through a multimode fiber using optical correlation

Damien Loterie, Bas Goorden, Demetri Psaltis, and Christophe Moser

Doc ID: 249908 Received 14 Sep 2015; Accepted 11 Nov 2015; Posted 12 Nov 2015  View: PDF

Abstract: We report on a method to obtain confocal imaging through multimode fibers using optical correlation. First, we measure the fiber's transmission matrix in a calibration step. This allows us to create focused spots at one end of the fiber by shaping the wavefront sent into it from the opposite end. These spots are scanned over a sample, and the light coming back from the sample via the fiber is correlated with the input pattern. We show that this achieves spatial selectivity in the detection. The technique is demonstrated on microbeads, a dried epithelial cell, and a cover glass.

Necklace Beam Generation in Nonlinear Colloidal Engineered Media

Natalia Litchinitser, Wiktor Walasik, and salih silahli

Doc ID: 250693 Received 23 Sep 2015; Accepted 09 Nov 2015; Posted 13 Nov 2015  View: PDF

Abstract: Modulational instability is a phenomenon that reveals itself as the exponential growth of weak perturbations in the presence of an intense pump beam propagating in a nonlinear medium. It plays a key role in such nonlinear optical processes as supercontinuum generation, light filamentation, and rogue waves. However, practical realization of these phenomena in the majority of available nonlinear media still relies on high-intensity optical beams. Here, we analytically and numerically show the possibility of necklace beam generation originating from low-intensity spatial modulational instability of vortex beams in engineered soft-matter nonlinear media.

Semi-analytical quasi-normal mode theory for the local density of states in coupled photonic crystal cavity-waveguide structures

Jakob Rosenkrantz de Lasson, Philip Kristensen, Jesper Mork, and Niels Gregersen

Doc ID: 250974 Received 28 Sep 2015; Accepted 09 Nov 2015; Posted 13 Nov 2015  View: PDF

Abstract: We present and validate a semi-analytical quasi-normal mode (QNM) theory for the local density of states (LDOS) in coupled photonic crystal (PhC) cavity-waveguide structures. By means of an expansion of the Green's function on one or a few QNMs, a closed-form expression for the LDOS is obtained, and for two types of two-dimensional PhCs, with one and two cavities side-coupled to an extended waveguide, the theory is validated against numerically exact computations. For the single cavity, a slightly asymmetric spectrum is found, which the QNM theory reproduces, and for two cavities a non-trivial spectrum with a peak and a dip is found, which is reproduced only when including both the two relevant QNMs in the theory. In both cases, we find relative errors below 1% in the bandwidth of interest.

Fiber-laser-based, green-pumped, picosecond optical parametric oscillator using fan-out grating PPKTP

Suddapalli Chaitanya Kumar, Shahrzad Parsa, and Majid Ebrahim-Zadeh

Doc ID: 250347 Received 17 Sep 2015; Accepted 09 Nov 2015; Posted 10 Nov 2015  View: PDF

Abstract: We report a stable, Yb-fiber-laser-based, green-pumped, picosecond optical parametric oscillator (OPO) for the near-infrared based on the nonlinear crystal, PPKTP, using fan-out grating design, and operating near room temperature. The OPO is continuously tunable across 726-955 nm in the signal and 1201-1998 nm in the idler, resulting in a total signal plus idler wavelength coverage of 1026 nm by grating tuning at a fixed temperature. The device generates up to 580 m W of average power in the signal at 765 nm and 300 mW in the idler at 1338 nm with an overall extraction efficiency of up to 52% and a pump depletion >76%. The extracted signal at 765 nm and idler at 1746 nm exhibit excellent passive power stability better than 0.5% and 0.8% rms, respectively, over 1 hour, in good beam quality with TEM00 mode profile. The output signal pulses have Gaussian temporal duration of 13.2 ps with a FWHM spectral bandwidth of 3.4 nm at 79.5 MHz repetition rate. Power scaling limitations of the OPO due to the material properties of PPKTP are studied.

Resonant evanescent Bessel beams on dielectric multilayers

Angelo Angelini

Doc ID: 250825 Received 25 Sep 2015; Accepted 09 Nov 2015; Posted 10 Nov 2015  View: PDF

Abstract: Complex light fields including evanescent Bessel beams can be generated at dielectric interfaces by means of oil-immersion optics operating in total internal reflection conditions. Here, we report on the observation of evanescent Bessel beams produced on a dielectric multilayer through the interference of surface modes resonantly sustained by the multilayer itself. The coupling to surface modes is attained by modifying the wavefront of an incident laser beam in such a way that the resulting intensity distribution in k-space matches the dispersion of the surface mode. The phase of surface modes can be further controlled and two-dimensional vortex beams can be also produced, according to the same working principle.

PT-symmetric phase in kagome photonic lattices

Gia-Wei Chern and Avadh Saxena

Doc ID: 250608 Received 25 Sep 2015; Accepted 08 Nov 2015; Posted 10 Nov 2015  View: PDF

Abstract: Kagome lattice is a two-dimensional network of corner-sharing triangles and is often associated with geometrical frustration. In particular, the frustrated coupling between waveguide modes in a kagome array leads to a dispersionless flat band consisting of spatially localized modes. Here~we propose a complex photonic lattice by placing PT-symmetric dimers at the kagome lattice points. Each dimer corresponds to a pair of strongly coupled waveguides. With balanced arrangement of gain and loss on individual dimers, the system exhibits a PT-symmetric phase for finite gain/loss parameter up to a critical value. The beam evolution in this complex kagome waveguide array exhibits a novel oscillatory rotation of optical power along the propagation distance. Long-lived local chiral structures originating from the nearly flat bands of the kagome structure are observed when the lattice is subject to a narrow beam excitation.

Femtosecond laser-induced surface structures on carbon fibers

Stephan Gräf, Roman Sajzew, Jan Schröder, Clemens Kunz, Sebastian Engel, and Frank Müller

Doc ID: 247614 Received 10 Aug 2015; Accepted 08 Nov 2015; Posted 16 Nov 2015  View: PDF

Abstract: The influence of different polarization states during the generation of periodic nanostructures on the surface of carbon fibers was investigated using a fs-laser with a pulse duration τ = 300 fs, a wavelength λ = 1025 nm and a peak fluence F = 4 J/cm². It was shown that linear polarization results in well-aligned periodic pattern with different orders of magnitude concerning their period and an alignment parallel and perpendicular to fiber direction, respectively. For circular polarization, both types of uniform LIPSS pattern appear simultaneously with different dominance in dependence on the position at the fiber surface. Their orientation was explained by the polarization-dependent absorptivity and the geometrical anisotropy of the carbon fibers.

Metamaterial-Waveguide Bends with effective bend-radius < λ0/2

Rajesh Menon, Bing Shen, and Randy Polson

Doc ID: 252418 Received 21 Oct 2015; Accepted 07 Nov 2015; Posted 13 Nov 2015  View: PDF

Abstract: We designed fabricated and characterized broadband, efficient, all-dielectric metamaterial-waveguide bends (MWBs) that redirect light by 180 degrees. The footprint of each MWB is 3μm X 3μm and redirection is achieved for single-mode waveguides spaced by 1.3μm, which corresponds to an effective bend radius of 0.65μm (<λ0/2 for λ0=1.55μm). The designed and measured transmission efficiencies are >80% and ~70%, respectively. Furthermore, the MWBs have an operating bandwidth >66nm (design) and >56nm (experiments). Our design methodology that incorporates fabrication constraints enables highly robust devices. The methodology can be extended to the general routing of light in tight spaces for large-scale photonic integration.

Compact and broadband polarization beam splitter based on a silicon nitride augmented low index guiding platform

Xiao Sun, MUHAMMAD ALAM, J. Stewart Aitchison, and Mo Mojahedi

Doc ID: 251722 Received 21 Oct 2015; Accepted 07 Nov 2015; Posted 24 Nov 2015  View: PDF

Abstract: We propose a compact polarization beam splitter (PBS) based on a silicon nitride enhanced silicon-on-insulator platform using augmented low index guiding (ALIG) waveguide structure. In the ALIG waveguide the TM mode is mostly confined in the lower index silicon nitride while the TE mode is confined in the high index silicon. Since the two modes are confined in two separate layers, their properties can be controlled independently. The PBS is formed using an asymmetric multimode interference (MMI) section. The TE mode is directed to one of the output waveguides by the multimode interferometer while the TM mode is directed to the other output by the ALIG waveguide. Such a PBS has a very small footprint, low insertion loss, high polarization extinction ratio and broadband response.

Measurement of the nonlinear refractive index of air constituents at mid-infrared wavelengths

Howard Milchberg, Sina Zahedpour, and Jared Wahlstrand

Doc ID: 251654 Received 09 Sep 2015; Accepted 06 Nov 2015; Posted 10 Nov 2015  View: PDF

Abstract: We measure the nonlinear refractive index coefficients in N2, O2 and Ar from visible through mid-infrared wavelengths (λ= 0.4 − 2.4 μm). The wavelengths investigated correspond to transparency windows in the atmosphere. Good agreement is found with theoretical models of χ(3). Our results are essential for accurately simulating the propagation of ultrashort mid-IR pulses in the atmosphere.

High-power, mid-infrared, picosecond pulses generated by compression of a CO₂ laser beat-wave in GaAs

Jeremy Pigeon, Sergei Tochitsky, and Chandrashekar Joshi

Doc ID: 250621 Received 23 Sep 2015; Accepted 06 Nov 2015; Posted 09 Nov 2015  View: PDF

Abstract: We report on the generation of a train of ~ 2 ps, 10 μm laser pulses via multiple four-wave mixing and compression of an infrared laser beat-wave propagating in the negative group velocity dispersion region of bulk GaAs and a combination of GaAs and NaCl. The use of a 200 ps, 106 GHz beat-wave, produced by combining laser pulses amplified on the 10P(20) and 10P(16) transition of a CO₂ laser, provides a novel method for generating high-power, picosecond, mid-IR laser pulses at a high repetition rate. By using 165 and 882 GHz beat-waves we show that cascaded phase-mismatched difference frequency generation plays a significant role in the four-wave mixing process in GaAs.

Self-mixing in low noise semiconductor vortex laser: detection of rotational Doppler shift in backscattered light

Arnaud Garnache, Seghilani Mohamed, Mikhaël Myara, Isabelle Sagnes, Baptiste Chomet, and Ryad BENDOULA

Doc ID: 249927 Received 11 Sep 2015; Accepted 05 Nov 2015; Posted 10 Nov 2015  View: PDF

Abstract: Light carrying orbital angular momentum L, scattered by a rotating object at angular velocity ω, experiences a rotational Doppler shift ω.L. We show that this fundamental light-matter interaction can be detected exploiting self-mixing in a vortex laser under Doppler shifted optical feedback, with quantum noise limited light detection. We used a low noise relaxation oscillation free (class-A) vortex laser, based on III-V semiconductor vertical-external-cavity-surface-emitting-laser technology, to generate coherent Laguerre-Gauss beams carrying L=h_bar l (l=± 1,..±4). Linear and rotational Doppler effects were studied experimentally and theoretically. This will allow to combine velocity sensor with an optical tweezers for micro-manipulation applications, with high performances : compact, powerful > 10mW, high quality beam, auto-aligned, linear response up to >10^8 rad/s or >300km/h , low back-scattered light detection limit <10^{-16}/Hz.

Model-based sensor-less wavefront aberration correction in optical coherence tomography

Hans Verstraete, Sander Wahls, Jeroen Kalkman, and Michel Verhaegen

Doc ID: 250676 Received 24 Sep 2015; Accepted 05 Nov 2015; Posted 06 Nov 2015  View: PDF

Abstract: Several sensor-less aberration correction methods that correct nonlinear wavefront aberrations by maximizing the OCT signal are tested on an optical coherence tomography (OCT) setup. A conventional coordinate search hill-climbing method is compared to two model-based optimization methods. The first model-based method takes advantage of the well-known optimization algorithm (NEWUOA) and utilizes a quadratic model. The second model-based method (DONE) is new and utilizes a random multi-dimensional Fourier basis expansion. The model-based algorithms achieve lower wavefront errors with up to ten times less measurements. Furthermore, the newly proposed DONE method outperforms the NEWUOA method significantly. The DONE algorithm is tested on OCT images and shows a significantly improved image quality.

Light absorption enhancement in elliptical nanohole array for photovoltaic application

Yonggang Wu, Zihuan Xia, Xuefei Qin, Yongdong Pan, Jian Zhou, and Zongyi Zhang

Doc ID: 251680 Received 09 Oct 2015; Accepted 05 Nov 2015; Posted 06 Nov 2015  View: PDF

Abstract: We propose a perpendicular elliptical silicon nanohole (PE-SiNH) array for light absorption in thin film silicon solar cells. Our analysis shows that this architecture is capable of increasing the absorption of a thin film silicon solar cell by 11.3% in comparison to that of the optimal circular SiNH array. Breaking the mirror symmetries is responsible for the increase of the coupled modes. The PE-SiNH structures show additional near-zero spatial Fourier components compared with the circular SiNH structure, which helps to couple more incident light into slow Bloch modes. The mode interaction between adjacent elliptical nanoholes is in favor of the coupling of the incident light into channeling modes and therefore enhances light absorption in the short wavelength region.

Raman linewidth measurements using time-resolved hybrid picosecond/nanosecond rotational CARS

Emil Nordström, Christian Brackmann, Per-Erik Bengtsson, Joakim Bood, and Ali Hosseinnia

Doc ID: 249269 Received 04 Sep 2015; Accepted 05 Nov 2015; Posted 06 Nov 2015  View: PDF

Abstract: We report an innovative approach for time-domain measurements of S-branch Raman linewidths using hybrid picosecond/nanosecond pure-rotational Coherent Anti-Stokes Raman Spectroscopy (RCARS). The Raman coherences are created by two picosecond excitation pulses and are probed using a narrow-band nanosecond pulse at 532 nm. This generates an RCARS signal which contains the entire coherence decay in a single pulse and permits temporal as well as spectral resolution through detection with a streak camera at the output of a spectrograph. By extracting the decay times of the individual transitions, the J-dependent Raman linewidths can be calculated. We report self-broadened S-branch linewidths for nitrogen (J’’=2-18) and oxygen (J’’=5-27) at 293 K and ambient pressure, which are in good agreement with previous time-domain measurements. Experimental considerations of the approach are discussed along with its merits and limitations. The approach can be extended to a wide range of pressures and temperatures and has potential for simultaneous single-shot thermometry and linewidth determination.

Effect of scanning beam size on the lateral resolution of mouse retinal imaging with SLOwith SLO

Pengfei Zhang, Mayank Goswami, Azhar Zam, Edward Pugh, and Robert Zawadzki

Doc ID: 248976 Received 01 Sep 2015; Accepted 04 Nov 2015; Posted 06 Nov 2015  View: PDF

Abstract: Scanning laser ophthalmoscopy (SLO) employs the eye’s optics as a microscope objective for retinal imaging in vivo. The mouse retina has become an increasingly important object of SLO imaging. In addition to its value for investigation of ocular disease and physiology with optogenetic probes, SLO imaging of the mouse eye can, in principle, achieve submicron lateral resolution thanks to a numerical aperture (NA) of ~ 0.5, about 2.5-fold larger than that of the human eye. In the absence of adaptive optics, however, natural ocular aberrations limit the SLO beam diameter useful for optimal resolution. The use of a contact lens can in principle correct many aberrations, permitting the use of a wider scanning beam and thus achieving greater resolution then would otherwise be possible. In this investigation, using an SLO equipped with a rigid contact lens, we report the effect of scanning beam size on the lateral resolution of mouse retinal imaging. Theory predicts that the maximum beam size Full Width at Half Maximum (FWHM) that can be used without any deteriorating effects of aberrations is ~ 0.6 mm. However, increasing the beam size up to the diameter of the dilated pupil is predicted to improve lateral resolution, though not to the diffraction limit. To test these predictions, the dendrites of a retinal ganglion cell expressing YFP were imaged and transverse scans analyzed to quantify the SLO system resolution. The results confirmed that lateral resolution increases with the beam size as predicted. With a 1.3 mm scanning beam and no high order aberration correction, the lateral resolution is ~ 1.15 m, superior to that achievable by most human AO-SLO systems. Advantages of this approach (in contrast with AO-SLO) to improving resolution in mouse SLO imaging are optical simplicity and a relatively wider field of view. © 2015 Optical Society of America

Revealing the Photophysics of Gold-Nanobeacons via Time-Resolved Fluorescence Spectroscopy

Yu Chen, Guoke Wei, DORIN SIMIONESIE, jan SEFCIK, Jens SUTTER, QINGJIANG Xue, Jun Yu, Jinliang Wang, and David Birch

Doc ID: 249669 Received 07 Sep 2015; Accepted 04 Nov 2015; Posted 09 Nov 2015  View: PDF

Abstract: We demonstrate that time-resolved fluorescence spectroscopy is a powerful tool to investigate the conformation states of hairpin DNA on the surface of gold nanoparticles (AuNPs) and energy transfer processes in Au-nanobeacons. Long-range fluorescence quenching of Cy5 by AuNPs has been found to be in good agreement with electrodynamics modelling. Moreover, time-correlated single-photon counting (TCSPC) is shown to be promising for real-time monitoring of the hybridization kinetics of Au-nanobeacons, with up to 60% increase in decay time component and 300% increase in component fluorescence fraction observed. Our results also indicate the importance of the stem and spacer designs for the performance of Au-nanobeacons.

Degenerate four-wave mixing in silicon hybrid plasmonic waveguides

Michael Nielsen, Stefano Palomba, Fernando Diaz, Stefan Maier, Rupert Oulton, and Thorin Duffin

Doc ID: 249798 Received 18 Sep 2015; Accepted 03 Nov 2015; Posted 06 Nov 2015  View: PDF

Abstract: Silicon-based plasmonic waveguides show high confinement well beyond the diffraction limit. Various devices have been demonstrated to outperform their dielectric counterparts at micrometer scales, such as linear modulators, capable of generating high field confinement and improving device efficiency by increasing access to nonlinear processes, limited by ohmic losses. By using hybridised plasmonic waveguide architectures and nonlinear materials, silicon-based plasmonic waveguides can generate strong nonlinear effects over just a few wavelengths. We have theoretically investigated the nonlinear optical performance of two hybrid plasmonic waveguides (HPWG) with three different nonlinear materials. Based on this analysis, the hybrid gap plasmon waveguide (HGPW), combined with the DDMEBT nonlinear polymer, shows a fourwave mixing (FWM) conversion efficiency of -16.4dB over a 1μm propagation length, demonstrating that plasmonic waveguides can be competitive with standard silicon photonics structures over distances three orders of magnitude shorter.

Ultrathin fiber-taper coupling with nitrogen vacancy centers in nanodiamonds at cryogenic temperatures

Masazumi Fujiwara, Zhao Hongquan, Tetsuya Noda, Kazuhiro Ikeda, Hitoshi Sumiya, and Shigeki Takeuchi

Doc ID: 250246 Received 18 Sep 2015; Accepted 02 Nov 2015; Posted 06 Nov 2015  View: PDF

Abstract: We demonstrate cooling of ultrathin fiber tapers coupled with nitrogen vacancy (NV) centers in nanodiamonds to cryogenic temperatures. Nanodiamonds containing multiple NV centers are deposited on the subwavelength 480-nm-diameter nanofiber region of fiber tapers. The fiber tapers are successfully cooled to 9 K using our special taper-mounting holder and an optimized cooling speed. The fluorescence from the nanodiamond NV centers is efficiently channeled into a single guided mode and shows characteristic sharp zero-phonon lines of both neutral and negatively charged NV centers. The present nanofiber/nanodiamond hybrid systems at cryogenic temperatures can be used as NV-based quantum information devices and for highly sensitive nanoscale magnetometry in a cryogenic environment.

Quantitative Fuel Vapor/Air Mixing Imaging in Droplet/Gas Regions of an Evaporating Spray Flow Using Filtered Rayleigh Scattering

Jeffrey Sutton, Patton Allison, and Thomas McManus

Doc ID: 249467 Received 04 Sep 2015; Accepted 30 Oct 2015; Posted 03 Nov 2015  View: PDF

Abstract: This paper demonstrates the application of filtered Rayleigh scattering (FRS) for quantitative two-dimensional fuel vapor and fuel vapor/air mixing measurements in an evaporating hydrocarbon fuel spray flow. Using the FRS approach, gas-phase measurements are made in the presence of liquid-phase droplets without interference. Effective suppression of the liquid-phase droplet scattering using FRS is enabled by the ultra-high spectral purity output of the current Nd:YAG laser system. Simultaneous Mie scattering imaging is used to visualize the droplet field and illustrate the level of droplet loading under which the FRS imaging is applied in the current evaporating spray flows. The initial quantification of the FRS imaging is based on calibration measurements from a flow cell of known fuel vapor/air mixtures, while future work targets the utilization of a Rayleigh-Brillouin spectral model for quantification of the FRS signals. Initial results using the Tenti S6 spectral model for select hydrocarbon fuels is presented.

Terahertz far-field super-resolution imaging through spoof surface plasmons illumination

Liu Pu-Kun and Heng-He Tang

Doc ID: 250855 Received 28 Sep 2015; Accepted 27 Oct 2015; Posted 03 Nov 2015  View: PDF

Abstract: The applications of terahertz (THz) imaging are always restricted by the low resolution. We introduce here a new way to realize far-field super-resolution imaging at THz frequency. Assisted by a new spoof surface plasmons (SSP) probe illumination, the images of two subwavelength separated slits can be reconstructed by a single shot. Although only 0.06λ resolution is numerically demonstrated at 0.3 THz, the resolution can be potentially further enhanced by scaling down the size of the SSP probe. Deep subwavelength focusing is also achieved by the SSP probe. Our work may open a new avenue for SSP-based super-resolution at longer wavelengths.

Enhanced upconversion of NaYF4:Er3+/Yb3+ phosphors prepared via the rapid microwave-assisted hydrothermal route at low temperature: phase and morphology control

Chung-Hsin Lu, Sudipta Som, SUBRATA DAS, and CHE-YUAN YANG

Doc ID: 250411 Received 21 Sep 2015; Accepted 25 Oct 2015; Posted 26 Oct 2015  View: PDF

Abstract: Monophasic NaYF4:Er3+/Yb3+ crystals were synthesized via the microwave-assisted hydrothermal route at 180°C. Microwave heating during the hydrothermal process substantially reduces the duration of reaction for the formation of cubic-NaYF4:Er3+/Yb3+ nanocrystals from 6 h to 30 min. As the duration of the reaction increases, cubic-NaYF4:Er3+/Yb3+ nanocrystals are transformed to uniform hexagonal-NaYF4:Er3+/Yb3+ microprisms because of the enhanced reaction kinetics. Bright upconverted emission from NaYF4:Er3+/Yb3+ crystal, obtained by the efficient two-photon excitation, is related to crystal structure and morphology. The hexagonal microprisms exhibit better upconversion and are employed in security applications.

Experimental demonstration of nonlinear pulse propagation in a fiber Bragg grating written in a fiber amplifier

Yuval Shapira, Vladimir Smulakovsky, and Moshe Horowitz

Doc ID: 250459 Received 21 Sep 2015; Accepted 25 Oct 2015; Posted 19 Nov 2015  View: PDF

Abstract: We study experimentally nonlinear propagation of sub-nanosecond optical pulses in a fiber Bragg grating written in a Ytterbium-doped fiber amplifier (YD-FBG). The magnitude and the sign of of group velocity dispersion (GVD) in YD-FBG can be controlled by adjusting the fiber tension. In case of anomalous GVD, pulse break-up was observed due to modulation instability. However, for the same input pulse power, in the normal GVD regime, the output pulse duration was increased and pulse break-up was not observed. The deterioration of pulse spectrum due to Raman and four wave mixing effect was also reduced in the normal GVD regime. Since GVD in YD-FBA is six orders of magnitude higher than in standard fibers, theadvantages of normal GVD in fiber amplifiers that were demonstrated in previous works for femtosecond and picosecond pulses can be exploited for amplifying sub-nanosecond pulses. The experimental results are in a good agreement with numerical simulations. We have also demonstrated a gain coefficient enhancement by a factor of 1.7 due to slow-light propagation in the YD-FBG.

Dual accelerating Airy-Talbot recurrence effect

Yiqi Zhang, Xing Liu, Milivoj Belic, Wei-Ping Zhong, Yanpeng Zhang, Min Xiao, and Hua Zhong

Doc ID: 250076 Received 15 Sep 2015; Accepted 23 Oct 2015; Posted 10 Nov 2015  View: PDF

Abstract: We demonstrate the dual accelerating Airy-Talbot recurrence effect, i.e., the self-imaging of accelerating optical beams, by propagating a superposition of Airy beams with successively changing transverse displacements. The dual Airy-Talbot effect is a spontaneous recurring imaging of the input and of the specific modulation of the input. An input composed of finite-energy Airy beams can also display the dual Airy-Talbot effect, but it demands a large transverse displacement and diminishes fast along the propagation direction. In fact, the Airy-Talbot effect is not strictly a Talbot effect, because a genuine Talbot requires the transverse periodicity, which is absent in Airy beams. Rather, the Airy-Talbot effect results from the constructive interference of Airy wave functions, which is also responsible for other kinds of Airy beams, for example, Airy breathers.

Spatial Resolution-Preserving Retroreflection for Gas-Phase Laser Scattering Measurements in Turbulent Flames Using a Phase Conjugate Mirror

Jeffrey Sutton, Daniel Marrinan, and Frederik Fuest

Doc ID: 247573 Received 11 Aug 2015; Accepted 14 Oct 2015; Posted 16 Oct 2015  View: PDF

Abstract: This paper reports on the demonstration of a stimulated Brillouin scattering phase conjugate mirror (SBS-PCM) for multi-pass laser-based scattering measurements in turbulent flames. Retro-reflective measurements using the SBS-PCM shows substantial improvements in spatial resolution preservation as compared to measurements using a conventional mirror as a multi-pass reflector. The results using the SBS-PCM indicate an insensitivity to large index-of-refraction gradients and preserves the original spatial resolution as defined by the laser beam under reacting flow conditions. This approach offers the possibility of increasing collected signals and signal-to-noise ratios within low-signal gas-phase scattering measurements such as Rayleigh and Raman scattering.

Actively mode-locked all fiber laser with cylindrical vector beam output

Anting Wang, Yong Zhou, Chun Gu, Lixin Xu, Feng Li, Dick Chung, and Qiwen Zhan

Doc ID: 247719 Received 14 Aug 2015; Accepted 12 Oct 2015; Posted 14 Oct 2015  View: PDF

Abstract: We demonstrated an all fiber actively mode-locked laser that emits cylindrical vector beam. An intra-cavity few-mode fiber Bragg grating inscribed in short section of four-mode fiber is employed to provide mode selection and spectrum filtering functions. Mode coupling is achieved by offset splicing between the single-mode fiber and the four-mode fiber in the laser cavity. A LiNbO3 Mach-Zehnder modulator is used to achieve active mode locking in the laser. The laser operates at 1547 nm with 30 dB spectrum width of 0.2 nm. The mode-locked pulses have a duration of 0.2 ns and repetition of 12.06 MHz. Through adjusting the polarization state in the laser cavity, both radially and azimuthally polarized beams have been obtained with high mode purity.

Design of 8-Mode Polarization-Maintaining Few-Mode Fiber for MIMO-free Spatial Division Multiplexing

Lixian Wang and Sophie LaRochelle

Doc ID: 250523 Received 22 Sep 2015; Accepted 29 Sep 2015; Posted 11 Nov 2015  View: PDF

Abstract: We propose a novel polarization-maintaining few-mode fiber that features an elliptical ring-shaped core with a high refractive index contrast ~0.03 between the core and the cladding. This fiber design alleviates the usual trade-off between the number of guided modes and the achievable birefringence that is usually observed in conventional elliptical-core few mode fibers. Through numerical simulations, we show that this fiber design can support up to ten guided vector modes over the entire C band while providing large birefringence. Except for the two fundamental modes, the eight higher-order vector modes are all separated from their adjacent modes by effective index differences >10-4, which is the typical birefringence value of single-mode polarization maintaining fibers. The designed fiber targets applications in spatial division multiplexing of optical channels, without multiple-input multiple-output digital signal processing, for short-reach optical interconnects.

Enhanced light extraction efficiency in organic light-emitting diode with randomly dispersed nanopattern

Yang Doo Kim, Kyung-Hoon Han, Yung-Hoon Sung, Jung-Bum Kim, Hak-Jong Choi, Heon Lee, and Jang-Joo Kim

Doc ID: 246919 Received 06 Aug 2015; Accepted 01 Sep 2015; Posted 16 Nov 2015  View: PDF

Abstract: An optical scattering layer comprising randomly dispersed nanorods was introduced in an organic light-emitting diode (OLED) to increase the out-coupling efficiency. A randomly dispersed nanopattern (RDNP) was fabricated by direct printing on a glass substrate. Owing to its low haze and high transmittance, the RDNP acted as light extraction layer in the OLED. The RDNP OLEDs showed higher current density and luminance, at the same voltage, than the reference device. The current and power efficiencies of the RDNP OLED increased by 25% and 34%, respectively, without electrical degradation. Furthermore, the RDNP devices achieved an external quantum efficiency of 27.5% at 1 mA/cm2.

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