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Applied Optics

L Cheng, T Chick, J Chapman, E F C Dreyer, C D Nie, S Bera, J A Harrington, S C Rand
Erbium-doped yttrium aluminum garnet (Er3+:YAG) rods were inserted inside undoped tubes and grown into single-crystal fibers of a diameter of 300 μm using the laser-heated pedestal growth technique. Growth at various rates resulted in radially graded distributions of Er3+ dopant ions, as observed using laser-induced fluorescence imaging. Profiles of the refractive index were measured using cross-sectional reflectometry in a microscope. Dopant distributions and the corresponding index profiles were compared with thermal diffusion theory to determine the inter-diffusion coefficient of Y3+ and Er3+ ions at 2000°C, yielding an estimated value of D=(9...
January 10, 2018: Applied Optics
Ce Bian, Manli Hu, Ruohui Wang, Tingting Gang, Rongxin Tong, Lisong Zhang, Teng Guo, Xiaobo Liu, Xueguang Qiao
An optical fiber humidity sensor based on an optical Fabry-Perot interferometer is proposed and experimentally demonstrated. The sensor is constructed by a short section of hollow-core fiber coated with a polyimide (PI) film. Taking advantage of the direct response of the PI film, a sensitivity of up to 1.309 nm/%RH can be achieved in the humidity change range from 40% RH to 80% RH. The temperature sensitivity is measured to be 43.57 pm/°C when the temperature changes from 25°C to 55°C. Because of its simple structure, fast response time, convenient production, and good reproducibility, the proposed sensor will be competitive in the field of cultural relic humidity monitoring and pharmaceutical storage...
January 10, 2018: Applied Optics
Jonas Gienger, Markus Bär, Jörg Neukammer
A method is presented to infer simultaneously the wavelength-dependent real refractive index (RI) of the material of microspheres and their size distribution from extinction measurements of particle suspensions. To derive the averaged spectral optical extinction cross section of the microspheres from such ensemble measurements, we determined the particle concentration by flow cytometry to an accuracy of typically 2% and adjusted the particle concentration to ensure that perturbations due to multiple scattering are negligible...
January 10, 2018: Applied Optics
Viktória Csajbók, Zsolt Bedőházi, Benedek J Nagy, Péter Dombi
Laser-induced damage threshold is a fundamental figure of merit of femtosecond optical components used in large-scale laser systems. We tested a series of ultrafast mirrors featuring high band-gap dielectric materials as well as improved design and coating techniques. In a broad range of the damage test pulse train involving between 10 and 100,000 pulses (40 fs, 800 nm), pure dielectric high reflectors exhibit around 1.5  J/cm2 and hybrid Ag-multilayer mirrors can exhibit well above 1.2  J/cm2 damage threshold...
January 10, 2018: Applied Optics
Jan Matrisch, Stefan Altmeyer
Simultaneous holographic multiplexing methods are used to store multiple holograms concurrently into one holographic volume. Compared to serial exposure, one advantage is the higher processing speed. Additionally, for parallel exposure the different gratings develop in a linear relation to one another, although the developing process itself is nonlinear caused by the holographic photopolymer. A mechano-optical modulator using a rotating optical flat is introduced to enable economic single-shot exposure of centimeter to decimeter-sized holograms utilizing only one laser...
January 10, 2018: Applied Optics
Sankaraganesh Jonna, Sukla Satapathy, Rajiv R Sahay
Today's smartphones/phablets/tablets are equipped with cameras that have enabled people to capture their favorite moments. However, images or videos taken at public places using inexpensive low-resolution cameras are often degraded by the presence of occlusions such as fences/barricades. In order to reconstruct a fence-free high-resolution image, we use a video of a scene captured by panning a hand-held camera and model the effects of various degradations. Initially, we obtain the spatial locations of fences by semantic segmentation and subsequently estimate the subpixel motion between the degraded low-resolution frames...
January 10, 2018: Applied Optics
Han Jia, Lijun Lu, Yiqing Cao
A calculation program of the modulation transfer function (MTF) of a fish-eye lens is developed with the autocorrelation method, in which the sixth-order wave aberration theory of ultra-wide-angle optical systems is used to simulate the wave aberration distribution at the exit pupil of the optical systems. The autocorrelation integral is processed with the Gauss-Legendre integral, and the magnification chromatic aberration is discussed to calculate polychromatic MTF. The MTF calculation results of a given example are then compared with those previously obtained based on the fourth-order wave aberration theory of plane-symmetrical optical systems and with those from the Zemax program...
January 10, 2018: Applied Optics
Juncheng Qiu, Jianqi Shen
Three methods for calculating the beam shape coefficients (the quadrature, the angular spectrum decomposition (ASD), and the localized approximation methods) are studied. The normalized associated Legendre function is employed in the calculation so as to prevent overflow. The two-dimensional integrations in the quadrature and the ASD methods are developed to the one-dimensional integration to speed up the calculation. The Gaussian beams reconstructed with different methods are compared, showing the difference in the remodeling effects of these methods...
January 10, 2018: Applied Optics
I Rehan, M Zubair Khan, K Rehan, A Mateen, M Aamar Farooque, S Sultana, Z Farooq
A spectrometer based on pulsed nanosecond laser-induced breakdown spectroscopy (LIBS) was employed for the quantitative determination of heavy and essential metals in salts from various sources available in Pakistan. Six salt samples were collected from sea salt and rock salt. Toxic metals (Cu, Cd, and Ni) and other microessentials (Fe, Ca, Co, Mg, Mn, S, and Zn) were investigated from the recorded spectra. The detection system was calibrated using a parametric dependence study. The quantitative analyses were accomplished under the assumption of local thermodynamic equilibrium and optically thin plasma...
January 10, 2018: Applied Optics
Fan Yang, Cheng Han, Bao-Xing Bai, Chao Zhang
In this paper, a projection correction method is proposed for autonomous-perception depth anisotropic surfaces, in order to improve the adaptive perceptual projection of the projection equipment under different circumstances. During the parameter calibration process of a projector-camera system with low recognition precision, as well as low noise resistance at angular points, an angular-point subpixel detection algorithm based on color information guidance was proposed to effectively improve the identification precision of the angular-point detection...
January 10, 2018: Applied Optics
Nazmi A Mohammed, Hatem O El Serafy
This work targets a remarkable quasi-distributed temperature sensor based on an apodized fiber Bragg grating. To achieve this, the mathematical formula for a proposed apodization function is carried out and tested. Then, an optimization parametric process required to achieve the remarkable accuracy that is based on coupled mode theory (CMT) is done. A detailed investigation for the side lobe analysis, which is a primary judgment factor, especially in quasi-distributed configuration, is investigated. A comparison between elite selection of apodization profiles (extracted from related literatures) and the proposed modified-Nuttal profile is carried out covering reflectivity peak, full width half maximum (FWHM), and side lobe analysis...
January 10, 2018: Applied Optics
Hee Jung Ryu, Jiyong Hwang, Jongyoon Kim, Ji-Hoon Lee
We investigated the dependence of the birefringence of polystyrene (PS) film with a negative optical birefringence on the stretching conditions. We varied the stretching ratio (SR), stretching speed (SS), and stretching temperature (ST), and measured the inplane birefringence and the Nz coefficient of the PS film. The inplane birefringence was increased with greater SR and SS but decreased with greater ST. The Nz coefficient of the stretched PS film was around zero and showed similar dependence on the stretching conditions like inplane birefringence...
January 10, 2018: Applied Optics
Qun Yuan, Zhishan Gao, Yimeng Dou, Yanxia Yao, Lu Chen
The ideal mapping geometry in a Fizeau interferometer is to map equal height increments on a flat object and equal angle increments on a spherical surface to equal heights on the detector. So the initial intent of the optical design of Fizeau transmission spheres (TSs) is to provide R-θ mapping geometry for equal angle increments. The corresponding unequal heights mapping will introduce retrace error as coma when linear carrier fringes exist. On the contrary, equal heights mapping with R-sin θ mapping geometry will avoid linear carrier fringes induced coma error...
January 10, 2018: Applied Optics
Xiaoliang Wang, Daru Chen, Haitao Li, Lijuan She, Qiong Wu
The random fiber laser (RFL), which is a milestone in laser physics and nonlinear optics, has attracted considerable attention recently. Most previously reported RFLs are based on distributed feedback of Rayleigh scattering amplified through the stimulated Raman-Brillouin scattering effect in single-mode fibers, which require long-distance (tens of kilometers) single-mode fibers and high threshold, up to watt level, due to the extremely small Rayleigh scattering coefficient of the fiber. We proposed and demonstrated a half-open-cavity RFL based on a segment of an artificially controlled backscattering single-mode fiber with a length of 210 m, 310 m, or 390 m...
January 10, 2018: Applied Optics
Qiliang Li, Shanshan Lu, Qi Bao, Dewang Chen, Miao Hu, Ran Zeng, Guowei Yang, Shuqin Li
In this paper, we propose a chaos-based scheme allowing for trilateral communication among three mutually coupled chaotic semiconductor lasers. The coupling through a partially transparent optical mirror between two lasers induces the chaotic dynamics. We numerically solve the delay rate equations of three lasers and demonstrate that the dynamics is completely synchronous. Herein, each laser is not only a transmitter but a receiver; three different messages are encoded by simultaneously modulating bias current of the three lasers...
January 10, 2018: Applied Optics
Yu Lee, Chanki Yu, Sang Wook Lee
We present a sequential fitting-and-separating algorithm for surface reflectance components that separates individual dominant reflectance components and simultaneously estimates the corresponding bidirectional reflectance distribution function (BRDF) parameters from the separated reflectance values. We tackle the estimation of a Lafortune BRDF model, which combines a nonLambertian diffuse reflection and multiple specular reflectance components with a different specular lobe. Our proposed method infers the appropriate number of BRDF lobes and their parameters by separating and estimating each of the reflectance components using an interval analysis-based branch-and-bound method in conjunction with iterative K-ordered scale estimation...
January 10, 2018: Applied Optics
Fangzhou Wang, Guoguo Kang
An improved bull's eye nanostructure is proposed as a substrate for surface-enhanced fluorescence. Optimized by finite-difference time-domain, annular corrugation on both upper and lower surfaces is placed around a nanobow tie in the middle. The whole structure is designed for the excitation and emission process of a certain fluorescence simultaneously, which can enhance the fluorescence intensity enormously (35 times for an excitation field and 120 times for radiation, independently). Meanwhile, it is able to confine the far-field emission energy within a divergence angle of ±3...
January 10, 2018: Applied Optics
Ning Wang, Ran Wang, Di Mo, Guangzuo Li, Keshu Zhang, Yirong Wu
A long-distance inverse synthetic aperture LADAR (ISAL) imaging experiment outdoors over 1 km for cooperative targets is demonstrated, which gets a two-dimensional high-resolution image with resolution exceeding 2.5 cm. The system utilizes an electro-optic in-phase and quadrature modulator to output a linear frequency-modulated continuous waveform (LFMCW) with a bandwidth of 6 GHz and pulse repetition frequency (PRF) of 16.7 KHz. For the problem of the coherence of the laser, the effects of the coherent processing interval (CPI) and time delay of the local oscillator (LO) on the coherence are discussed...
January 10, 2018: Applied Optics
Kayori Takahashi, Seika Ohuchi, Keizo Saito, Makoto Hirasawa, Hiromu Sakurai
The preparation of nanoscale fine bubbles in water is an innovative technology, but no precise method for simultaneously measuring the size and concentration of such bubbles had previously been developed. We have developed a method for simultaneously determining the size and concentration of fine bubbles in water by a light-scattering technique. Dynamic light scattering gives the diffusion constant and particle size of fine bubbles, whereas static light scattering provides their concentration or molar mass...
January 10, 2018: Applied Optics
L M Riobo, F E Veiras, M G Gonzalez, M T Garea, P A Sorichetti
This paper describes the design and performance of a phase demodulation scheme based on software-defined radio (SDR), applied in heterodyne interferometry. The phase retrieval is performed in real time by means of a low-cost SDR with a wideband optoelectronic front-end. Compared to other demodulation schemes, the system is quite simpler, versatile, and of lower cost. The performance of the demodulator is demonstrated by measuring the displacement per volt of a thin-film polymeric piezoelectric transducer based on polyvinylidene fluoride for ultrasonic applications...
January 10, 2018: Applied Optics
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