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Applied Optics

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https://www.readbyqxmd.com/read/29877401/switchable-microwave-photonic-filter-based-on-a-dual-parallel-mach-zehnder-modulator
#1
Ling Wang, Chengwu Yang, Ming Li, Ninghua Zhu, Wei Li
We present a switchable and tunable microwave photonic filter (MPF) based on a dual-parallel Mach-Zehnder modulator (DPMZM) and a tunable optical bandpass filter (TOBPF). The MPF is switchable between low-pass and bandpass responses by simply tuning the bias voltage of the DPMZM. In addition, the MPF is widely tunable in terms of bandwidth and center frequency by adjusting the TOBPF.
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877400/transport-based-model-for-turbulence-corrupted-imagery
#2
J M Nichols, T H Emerson, L Cattell, S Park, A Kanaev, F Bucholtz, A Watnik, T Doster, G K Rohde
A new model for turbulence-corrupted imagery is proposed based on the theory of optimal mass transport. By describing the relationship between photon density and the phase of the traveling wave, and combining it with a least action principle, the model suggests a new class of methods for approximately recovering the solution of the photon density flow created by a turbulent atmosphere. Both coherent and incoherent imagery are used to validate and compare the model to other methods typically used to describe this type of data...
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877399/multifocus-image-fusion-method-for-image-acquisition-of-3d-objects
#3
Changsheng Li, Xianmin Zhang, Heng Wu
We propose a multifocus image fusion method for achieving all-in-focus images of three-dimensional objects based on the combination of transform domain and spatial domain techniques. First, the source images are decomposed into low-frequency and high-frequency components by the discrete wavelet transform technique. Next, a correlation coefficient is employed to obtain the maximum similarity among low-frequency components. Then, in order not to interrupt the correlations among decomposition layers, the comparison among high-frequency components is executed by transforming them to spatial domain...
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877398/calibration-and-validation-of-airborne-multiangle-spectropolarimetric-imager-airmspi-polarization-measurements
#4
Gerard van Harten, David J Diner, Brian J S Daugherty, Brian E Rheingans, Michael A Bull, Felix C Seidel, Russell A Chipman, Brian Cairns, Andrzej P Wasilewski, Kirk D Knobelspiesse
The Airborne Multiangle SpectroPolarimetric Imager (AirMSPI), a precursor to the future Multi-Angle Imager for Aerosols satellite instrument, is a remote-sensing instrument for the characterization of atmospheric aerosols and clouds. To help discriminate between different aerosol particle types, which is crucial to improve our understanding of their impact on climate and air quality, AirMSPI acquires imagery over multiple view angles in the ultraviolet, visible, and near-infrared, and it employs dual photoelastic modulators (PEMs) to target an uncertainty requirement of ±0...
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877397/opsr-enhancement-of-high-temperature-operating-shallow-surface-grating-vcsels
#5
Yingying Liu, Xing Zhang, Youwen Huang, Jianwei Zhang, Werner Hofmann, Yongqiang Ning, Lijun Wang
A polarization-stable single-mode 894 nm vertical cavity surface emitting laser (VCSEL) with an orthogonal polarization suppression ratio of 30 dB, even at a temperature up to 80°C, was achieved for atomic clock applications by utilizing shallow-surface gratings. An improved grating VCSEL fabrication technology for mass production was also proposed by taking advantage of the displacement Talbot lithography. The multi-mode grating VCSEL was also measured for other applications that need polarization stability, such as doubled-data-rate polarization multiplexed free-space links...
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877396/symbol-by-symbol-exp-log-transceiver-design-for-simo-fso-communication-systems-in-correlated-lognormal-channels
#6
Ru-Han Chen, Jian Zhang, Yan-Yu Zhang
In this paper, assuming only channel statistics information available at the receivers, we propose a transceiver design for single-input multiple-output (SIMO) free-space optical (FSO) systems over weak atmospheric turbulence, which is described by spatially correlated lognormal fading channels. To mitigate turbulence-induced spatially correlated lognormal fading, we investigate the symbol-by-symbol decision criterion and develop a low-complexity, energy-efficient transceiver by exploiting the joint spatial distribution of log irradiance...
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877395/polarization-independent-atomic-prism-filter-for-removing-amplified-spontaneous-emission
#7
Raphael David Cohen, Christopher A Mullarkey, John C Howell, Nadav Katz
We create an optical frequency, polarization-independent, narrow bandpass filter of 1.3 GHz (3 dB bandwidth), using the steep dispersion near the rubidium D1 atomic transitions within a prism-shaped vapor cell. This enables us to clean the amplified spontaneous emission from a laser by more than 3 orders of magnitude. Such a filter could find uses in fields such as quantum information processing and Raman spectroscopy.
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877394/pressure-characteristics-of-a-self-q-switched-distributed-bragg-reflector-fiber-laser
#8
Chengang Lyu, Xugeng Zhang, Shuai Zhang, Gan Fang, Jie Jin
Based on the study of self-Q-switching of a short cavity erbium-doped distributed Bragg reflector (DBR) fiber laser in time domain, the influence of pressure disturbance on the self-Q-switched output is analyzed. In the experiment, the erbium-doped DBR fiber laser (EDFL) was encapsulated with epoxy resin and curing agent to protect and sensitize the fiber. The EDFL sends out self-Q-switched laser pulses when the pump power of the 980 nm laser source is more than 110 mW. The external pressure is exerted on the DBR fiber and increased gradually from 0 g (0 N) to 120 g (1...
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877393/addressable-spatial-light-modulators-for-eye-tracking-autostereoscopic-three-dimensional-display-using-a-scanning-laser
#9
Zhenfeng Zhuang, Lei Zhang, Phil Surman, Weitao Song, Simon Thibault, Xiao Wei Sun, Yuanjin Zheng
A scanning laser-based back light three-dimensional (3D) display capable of rendering full-resolution, low crosstalk, and vivid 3D depth perception has been developed by incorporating time-sequential multiplexing and eye-tracking technologies. This system includes three main subsystems: a scanning laser module, a relay transfer unit created by combining multiple transmissive-type electrically addressed ferroelectric liquid crystal spatial light modulators (FLC-SLMs), and a dual-directional transmission screen (DDTS) unit that can produce different angular magnification factors in both the tangential and sagittal planes...
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877392/transport-of-intensity-computational-ghost-imaging
#10
Koshi Komuro, Yuya Yamazaki, Takanori Nomura
Computational ghost imaging (CGI) allows us to obtain a sample image under a low signal-to-noise-ratio (SNR) condition. However, phase information cannot be obtained by CGI; therefore, observation of transparent objects such as living cells is difficult. Although interferometry has been applied to CGI for phase retrieval, its optical setup is cumbersome. In this paper, an alternative approach, which is based on a transport-of-intensity equation, is proposed. Compared with conventional interferometric methods, the optical setup of the proposed method is robust because it does not require additional optical elements...
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877391/perturbative-solution-to-the-two-component-atmosphere-dial-equation-for-improving-the-accuracy-of-the-retrieved-absorption-coefficient
#11
Catharine E Bunn, Kevin S Repasky, Matthew Hayman, Robert A Stillwell, Scott M Spuler
Thermodynamic profiling using ground-based remote sensing instruments such as differential absorption lidar (DIAL) has the potential to fill observational needs for climate and weather-related research and improve weather forecasting. The DIAL technique uses the return signal resulting from atmospherically scattered light at two closely spaced wavelengths to determine the range-resolved absorption coefficient for a molecule of interest. Temperature profiles can be retrieved using a temperature-sensitive absorption feature of a molecule with a known mixing ratio such as oxygen...
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877390/scalable-and-reconfigurable-true-time-delay-line-based-on-an-ultra-low-loss-silica-waveguide
#12
Qian Qian Song, Zhe Feng Hu, Kai Xin Chen
A scalable and reconfigurable on-chip optical true time delay line consisting of Mach-Zehnder interferometer (MZI) switches and delay waveguides is proposed and demonstrated with the ultra-low-loss silica waveguide platform. The MZI switches provide the reconfiguration of the light traveling paths and hence different delays. Our proposed structure can be easily scaled to an M bit delay line with a slight increase in dimensions. The footprint of our fabricated 1 bit delay line is 33  mm×13  mm (length×width) and can provide a delay of 6...
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877389/simultaneous-measurement-of-group-and-phase-refractive-indices-and-physical-thickness-of-transparent-plates-with-low-coherence-fabry-perot-interferometry
#13
David J Bang, Yudeuk Kim, Yoohan Kim, Myung-Jik Kim, Kyong Hon Kim
We introduce a new method for simultaneously measuring group and phase refractive indices, the dispersion profile, and the physical thickness of transparent plates by using low coherent Fabry-Perot (FP) interferometry without using any mechanical scanning and sample rotation. A broadband infrared light source was used for a fiber-type FP interferometer, and the Fourier transform analysis on the measured interference spectra was performed to determine the refractive indices and thickness of BK7, quartz, and fused silica samples over its wavelength range...
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877388/diffraction-efficiency-performance-of-random-anti-reflecting-subwavelength-surface-structures-on-prefabricated-fused-silica-binary-gratings
#14
Karteek Kunala, Menelaos K Poutous
Random anti-reflecting subwavelength surface structures have been reported to enhance transmission of optical windows and lenses. Specifically, for fused silica substrates, 99.9% specular transmission has been verified by various groups. Diffractive optical elements, such as gratings, also experience net Fresnel losses on both their planar and structured surfaces. We investigated the performance of prefabricated 50% duty-cycle, binary, fused silica linear gratings, with a period of 1.6 μm, before and after application of random anti-reflecting subwavelength surface structures, in order to reduce their initial Fresnel reflectivity...
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877387/experiment-on-the-temporal-evolution-characteristics-of-a-ccd-multilayer-structure-irradiated-by-a-1-06-%C3%AE-m-continuous-laser
#15
Min Han, Jinsong Nie, Ke Sun, Xi Wang, Xian'an Dou
In this study, an experiment of a CCD detector irradiated by a 1.06 μm continuous laser is established. Factors including the microlens focusing beam, microlens carbonization at high temperature, shading aluminum film opening rate, low shading aluminum film absorption rate, and different materials' absorption to the laser are comprehensively considered. By combining the irradiation time, the output image of the CCD detector, surface morphology of the damage area, the optical micrograph, and regional energy spectrogram, the damage mechanism of the CCD is explored...
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877386/analysis-of-the-optical-center-position-of-an-optical-system-of-a-camera-lens
#16
Antonín Mikš, Jiří Novák
A theory of an optical center of a camera lens is described. The concept of an optical center (a camera center) is used widely in various methods dedicated to the calibration of optical imaging and measuring systems in photogrammetry, computer vision, triangulation sensors, fringe projection techniques, surveying, and machine vision, where the so-called pinhole camera model is used as the camera's basic model. It is shown that the optical center of the optical system with a fixed position does not exist generally, even for an ideal optical system...
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877385/simultaneous-sum-frequency-and-second-harmonic-generation-in-a-planar-waveguide
#17
Pragati Aashna, K Thyagarajan
In this paper, we analyze second-harmonic (SH) generation and sum-frequency (SF) generation in a planar waveguide configuration using 2D quasi-phase-matching (QPM) gratings and show possibility of simultaneous generation of sum frequency and second harmonic. It is shown that it is possible for the two generated frequencies to be noncollinear with respect to the incident pump waves with the SF and SH frequencies exiting at different angles along the planar waveguide, leading to ease of collection. Numerical simulations are performed in a potassium titanyl phosphate planar waveguide, and it is shown that the proposed planar waveguide configuration provides wavelength tunability and has greater conversion efficiencies than bulk configuration and larger bandwidth than channel waveguide configuration...
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877384/evaluation-of-the-pmma-microlens-efficiency-for-the-realization-of-a-solar-micro-concentrator-array
#18
F Loffredo, F Villani, C Cancro, G Nenna, A Borriello, R Miscioscia, C Minarini, F Roca
In order to assess the performance of solar micro-concentrators, specific methods and protocols need to be developed, tested, and applied. In detail, as in conventional concentration modules, one of the fundamental parameters to consider is the efficiency of optical concentrators. In fact, optical concentrators give fundamental information on the current potentially generated from solar microcells that receive the concentrated light radiation. To develop a measurement method for micrometer-size optical components, a suitable optical system was implemented and used...
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877383/high-efficiency-directional-backlight-design-for-an-automotive-display
#19
Bo-Tsuen Chen, Jui-Wen Pan
We propose a high-efficiency directional backlight module (DBM) for automotive display applications. The DBM is composed of light sources, a light guide plate (LGP), and an optically patterned plate (OPP). The LGP has a collimator on the input surface that serves to control the angle of the light emitted to be in the horizontal direction. The OPP has an inverse prism to adjust the light emission angle in the vertical direction. The DBM has a simple structure and high optical efficiency. Compared with conventional backlight systems, the DBM has higher optical efficiency and a suitable viewing angle...
June 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29877382/experimental-investigation-on-a-nonuniformly-correlated-partially-coherent-laser
#20
Chengcheng Chang, Xudong Chen, Ziyang Chen, Zhili Lin, Xiaoyan Li, Jixiong Pu
We demonstrate, to the best of our knowledge, a new kind of laser, called a partially coherent digital laser, producing nonuniformly correlated partially coherent light beams by "playing a video" inside the cavity directly. In this laser, a spatial light modulator (SLM) with dynamic phase modulation acts as a cavity mirror. The coherence degree distribution of the output beams can be controlled simply by varying the waists of the computer-generated holograms on the SLM. The experimental results show that the coherence degree between two points on the observation plane is not only dependent on the distance between them, but also on the positions that are observed across the beam...
June 1, 2018: Applied Optics
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