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Applied Optics

Wen Chen
Computer-generated holograms (CGHs) have attracted more and more attention in some application fields, such as 3D displays, optical security, and beam shaping. In this paper, a strategy is presented for optical information verification based on CGH using binary phase (1 bit) with an aperture. The input is encoded into the cascaded phase-only masks based on CGH via iterative phase retrieval, and one extracted phase mask is binarized in which one part is selected according to an aperture and further embedded into a random binary-phase host mask...
November 10, 2017: Applied Optics
Jing Chen, Jin Hu, Xiao-Bo Yang, Xiang-Yang Lu
Estimating the chirpiness of a spatial chirp signal is important in many optical engineering applications. With the help of transformation optics, a new kind of fractional Fourier transform lens is designed by deforming the conventional graded index lens through conformal mapping, which can manipulate the chirpiness of the input chirp signal. The low-input chirpiness is magnified by the transformation material, and the error of the detection is kept approximately the same; thus, the designed lens has enhanced chirpiness detection precision and distinguishability for low chirpiness...
November 10, 2017: Applied Optics
Junjie Sun, Zefeng Wang, Meng Wang, Zhiyue Zhou, Ni Tang, Jinbao Chen, Xijia Gu
A watt-level tunable 1.5 μm narrow linewidth fiber ring laser using a temperature tuning π-phase-shifted fiber Bragg grating (π-PSFBG) is demonstrated here, to the best of our knowledge, for the first time. The π-PSFBG is employed as both a narrow band filter and a wavelength tuning component, and its central wavelength is thermally tuned by a thermo-electric cooler. The maximum laser power is about 1.1 W with a linewidth of ∼318  MHz (∼2.57  pm) and a power fluctuation of less than 3%. The wavelength tuning range of the laser is about 1...
November 10, 2017: Applied Optics
V V Marinyuk, S V Sheberstov
We study the total bulk reflectance of a turbid medium with large (as compared to the light wavelength) inhomogeneities at grazing angles of light incidence. To model highly forward scattering in the medium, we take advantage of the Reynolds-McCormick scattering phase function. Using the scaling analysis for the small-angle radiative transfer equation, we derive simple analytical formulas for the total reflectance. For grazing incidence angles, we find a range of values of the medium transport coefficients where the total reflectance proves to be a universal function of a single parameter, which is expressed in terms of the incidence angle, the absorption coefficient, and the transport scattering one...
November 10, 2017: Applied Optics
Longxiang Li, Donglin Xue, Weijie Deng, Xu Wang, Yang Bai, Feng Zhang, Xuejun Zhang
In deterministic computer-controlled optical surfacing, accurate dwell time execution by computer numeric control machines is crucial in guaranteeing a high-convergence ratio for the optical surface error. It is necessary to consider the machine dynamics limitations in the numerical dwell time algorithms. In this paper, these constraints on dwell time distribution are analyzed, and a model of the equal extra material removal is established. A positive dwell time algorithm with minimum equal extra material removal is developed...
November 10, 2017: Applied Optics
Maria I Comanici, Lawrence R Chen, Peter Kung
Fiber optic sensors based on fiber Bragg gratings (FBGs) find potential use in condition monitoring because their spectral properties change according to external environmental and/or physical factors. We propose and demonstrate a technique for interrogating multiple FBG-based sensors based on microwave photonic (MWP) filtering. In particular, we exploit the spectrum-slicing properties of two different FBG Fabry-Perot cavities to implement a double passband MWP filter. Each sensor spectrum results in a unique MWP filter passband...
November 10, 2017: Applied Optics
Guo Xia, Su Wu, Guodong Wang, Mingyong Hu, Jinyu Xing
A modified optical design for a broadband, high resolution, astigmatism-free Czerny-Turner spectrometer is proposed. Astigmatism is corrected by using cylindrical mirrors over a broad spectral range. The theory and method for astigmatism correction are thoroughly analyzed. The comparison between the modified Czerny-Turner spectrometer and the traditional Czerny-Turner spectrometer is also described in detail. The ray-tracing results show that the RMS spot radius has decreased to 4.2 μm at the central wavelength and 17 μm at the wedge wavelength...
November 10, 2017: Applied Optics
Zhenfeng Zhuang, Phil Surman, Simon Thibault
An iterative optimization algorithm is introduced to address the surface iterative errors as well as source extension issues in a freeform illumination system for producing satisfactory illumination distribution. A unique two-parameter coordinate system is utilized to represent the emitted ray directions. Then, the direction vector for the incident rays, which propagate through several surfaces, is obtained using ray-tracing techniques. Based on the mapping between the incoming rays and a target grid, a freeform surface is generated as a good starting design...
November 10, 2017: Applied Optics
Maïté Louisy, Chen Guo, Lana Neoričić, Shiyang Zhong, Anne L'Huillier, Cord L Arnold, Miguel Miranda
We present a compact implementation of the ultrashort pulse measurement technique based on dispersion scans (d-scan), allowing single-shot measurement of few-cycle pulses. The main novelty in our design, making our setup extremely compact and simple, is the use, after a prism, of a spherical mirror in an off-axis geometry. The intentionally introduced strong astigmatism makes it possible to image the output of the crystal in one direction while focusing it in the other direction, resulting in the output face of the prism being imaged into a line in the second-harmonic crystal...
November 10, 2017: Applied Optics
Haiyang Xu, Man Jiang, Pu Zhou, Guomin Zhao, Xijia Gu
Sustained self-pulsing and self-mode-locking (SML) are detrimental to the performance of continuous-wave (CW) fiber lasers. We demonstrate an all-fiber method to eliminate SML pulsing by employing a low-reflectivity fiber Bragg grating (FBG) outside of a laser cavity to provide feedback. A narrow-bandwidth FBG is used to form an external cavity with the output coupler FBG, which suppresses the SML up to a certain output power level, at which point, the laser emission linewidth is still within the bandwidth of the FBG...
November 10, 2017: Applied Optics
Christian Lemmerz, Oliver Lux, Oliver Reitebuch, Benjamin Witschas, Christian Wührer
We report on the design and performance of the laser deployed in the airborne demonstrator Doppler wind lidar for the Aeolus mission of the European Space Agency (ESA). The all-solid-state, diode-pumped and frequency-tripled Nd:YAG laser is realized as a master oscillator power amplifier (MOPA) system, generating 60 mJ of single-frequency pulses at 355 nm wavelength, 50 Hz repetition rate and 20 ns pulse duration. For the measurement of the Doppler frequency shift over several accumulated laser shots, the frequency stability of the laser is of crucial importance...
November 10, 2017: Applied Optics
Thomas Bennett, Matthew Proctor, Jon Forster, Eleni Perivolari, Nina Podoliak, Matthew Sugden, Roger Kirke, Thomas Regrettier, Thomas Heiser, Malgosia Kaczmarek, Giampaolo D'Alessandro
We track the non-uniformity of a wide area liquid crystal device using multiple cross-polarized intensity measurements. They give us not only accurate estimates of the core physical liquid crystal parameters, such as elastic constants, but also spatial maps of the device properties, including the liquid crystal thickness and pretilt angle. A bootstrapping statistical analysis, coupled with the multiple measurements, gives us reliable error bars on all the measured parameters.
November 10, 2017: Applied Optics
Cheng Feng, Yijun Zhang, Jian Liu, Yunsheng Qian, Xinxin Liu, Feng Shi, Hongchang Cheng
The graded bandgap AlxGa1-xAs/GaAs photocathode with graded composition and exponential doping structure has shown great potential for improving photoemission capability. In order to better study the performance of transmission-mode AlxGa1-xAs/GaAs photocathode with the complex graded bandgap structure, the experimental optical properties and quantum efficiency are measured by comparison with uniform composition and exponential doping Al0.7Ga0.3As/GaAs photocathode. The theoretical optical properties of the multilayer AlxGa1-xAs/GaAs photocathode modules are calculated by matrix formula on the basis of thin-film optical principles...
November 10, 2017: Applied Optics
Shlomi Lightman, Gilad Hurvitz, Raz Gvishi, Ady Arie
Conversion of a Gaussian beam into a top-hat beam or to an annular beam is demonstrated using 3D direct laser printing. Micron-scale refractive phase elements were designed and printed directly on standard commercially available lenses. These structures modify the phase of the incoming beam into either three intensity-flattened profiles, having line, square, or circular shapes, or to an annular beam profile. This method to functionalize lenses opens new and exciting opportunities for compact and robust beam shaping, as well as for reduction of the aberrations of the lens itself...
November 10, 2017: Applied Optics
Hieu Nguyen, Zhaoyang Wang, Patrick Jones, Bing Zhao
Consumer-grade red-green-blue and depth (RGB-D) sensors, such as the Microsoft Kinect and the Asus Xtion, are attractive devices due to their low cost and robustness for real-time sensing of depth information. These devices provide the depth information by detecting the correspondences between the captured infrared (IR) image and the initial image sent to the IR projector, and their essential limitation is the low accuracy of 3D shape reconstruction. In this paper, an effective technique that employs the Kinect sensors for accurate 3D shape, deformation, and vibration measurements is introduced...
November 10, 2017: Applied Optics
J Pablo La Torre, Nathan Mayes, Nabeel A Riza
Proposed is a laser projection display system that uses an electronically controlled variable focus lens (ECVFL) to achieve sharp and in-focus image projection over multi-distance three-dimensional (3D) conformal screens. The system also functions as an embedded distance sensor that enables 3D mapping of the multi-level screen platform before the desired laser scanned beam focused/defocused projected spot sizes are matched to the different localized screen distances on the 3D screen. Compared to conventional laser scanning and spatial light modulator (SLM) based projection systems, the proposed design offers in-focus non-distorted projection over a multi-distance screen zone with varying depths...
November 10, 2017: Applied Optics
Chen Xu, Dewen Cheng, Yongtian Wang
The degree of automation in optical design has always been improving, and several human-competitive automatic lens design programs have been developed. However, to the best of our knowledge, no such work on off-axis systems has been reported, which we think is largely due to the complicated unfeasible conditions caused by obscuration. Here, we propose a model to detect and evaluate the degree of obscuration for off-axis mirror systems and also a method to automatically eliminate the obscuration by structural optimization...
November 10, 2017: Applied Optics
Hongpeng Liu, Dan Yu, Ke Zhou, Shichan Wang, Suhua Luo, Weibo Wang, Qinggong Song
A novel thermo-sensitive N-isopropylacrylamide photopolymer was developed for improving the temperature and humidity responses of holographic sensors. Diffraction spectra of holographic volume gratings recorded in the materials were characterized to explore the sensing response capacity. A dependence of peak wavelength on the temperature was observed and provided a quantitative strategy for holographic sensing applications. Expansion of the humidity range induced a strong extension of wavelength shift. Finally, the temperature response reversibility was demonstrated experimentally...
November 10, 2017: Applied Optics
Juanjuan Zheng, Peng Gao, Xiaopeng Shao, G Ulrich Nienhaus
Opposed-view digital holographic microscopy (OV-DHM) with autofocusing and out-of-focus background suppression was demonstrated and applied to measure the refractive index (RI) of suspended HeLa cells. In OV-DHM, a specimen is illuminated from two sides in a 4π-like configuration. The generated two opposite-view object waves, which have orthogonal polarization orientations, interfere with a common reference wave, and the generated holograms are recorded by a CMOS camera. The image plane of the sample was determined by finding the minimal variation between the two object waves...
November 10, 2017: Applied Optics
Yusuke Nagai, Chen Shao-Chieh, Kotaro Kajikawa
A random laser of a photonic crystal fiber (PCF) with holes filled with laser dye-doped nematic liquid crystal (NLC) is reported. When the excitation polarization was along the PCF axis, the measured laser threshold was 80  μJ/mm(2) per pulse, which is much lower than the previously reported random laser of PCF filled with laser dye-doped organic solvent. This low threshold is due to the high refractive index of the NLC, which produces a greater scattering efficiency. In contrast, when the excitation polarization is perpendicular to the PCF axis, the threshold was much higher or the laser oscillation was absent...
November 10, 2017: Applied Optics
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