47,667 results match your criteria Applied optics[Journal]


Switchable microwave photonic filter based on a dual-parallel Mach-Zehnder modulator.

Appl Opt 2018 Jun;57(16):4537-4541

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. Read More

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June 2018
2 Reads

Transport-based model for turbulence-corrupted imagery.

Appl Opt 2018 Jun;57(16):4524-4536

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. Read More

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June 2018
1 Read

Multifocus image fusion method for image acquisition of 3D objects.

Appl Opt 2018 Jun;57(16):4514-4523

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. Read More

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June 2018
1 Read

Calibration and validation of Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) polarization measurements.

Appl Opt 2018 Jun;57(16):4499-4513

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 ±0.005 in the degree of linear polarization (DoLP) at selected wavelengths. Read More

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June 2018
4 Reads

OPSR enhancement of high-temperature operating shallow-surface grating VCSELs.

Appl Opt 2018 Jun;57(16):4486-4490

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. Read More

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June 2018
2 Reads

Symbol-by-symbol exp-log transceiver design for SIMO FSO communication systems in correlated lognormal channels.

Appl Opt 2018 Jun;57(16):4477-4485

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. Different from existing symbol-by-symbol detection schemes, the proposed transceiver has a simple structure with asymptotical performance compared to maximum-likelihood (ML) detection and flexible modulation schemes. Read More

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June 2018
1 Read

Polarization-independent atomic prism filter for removing amplified spontaneous emission.

Appl Opt 2018 Jun;57(16):4472-4476

We create an optical frequency, polarization-independent, narrow bandpass filter of 1.3 GHz (3 dB bandwidth), using the steep dispersion near the rubidium D 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. Read More

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June 2018
1 Read

Pressure characteristics of a self-Q-switched distributed Bragg reflector fiber laser.

Appl Opt 2018 Jun;57(16):4467-4471

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. Read More

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June 2018
2 Reads

Addressable spatial light modulators for eye-tracking autostereoscopic three-dimensional display using a scanning laser.

Appl Opt 2018 Jun;57(16):4457-4466

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. The light beam is directed by the DDTS after transmission through FLC-SLMs, and left and right eye viewing zones are produced sequentially in accordance with the locations of clear apertures in the FLC-SLM that are controlled based on data from the eye-tracking system. Read More

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June 2018
1 Read

Transport-of-intensity computational ghost imaging.

Appl Opt 2018 Jun;57(16):4451-4456

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. Read More

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June 2018
1 Read

Perturbative solution to the two-component atmosphere DIAL equation for improving the accuracy of the retrieved absorption coefficient.

Appl Opt 2018 Jun;57(16):4440-4450

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. Read More

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June 2018
1 Read

Scalable and reconfigurable true time delay line based on an ultra-low-loss silica waveguide.

Appl Opt 2018 Jun;57(16):4434-4439

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. Read More

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June 2018
1 Read

Simultaneous measurement of group and phase refractive indices and physical thickness of transparent plates with low coherence Fabry-Perot interferometry.

Appl Opt 2018 Jun;57(16):4428-4433

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. The accuracy of the physical thickness of the samples was obtained within an order of 1 μm scale, while that of both the group and the phase refractive indices was within the third decimal point. Read More

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June 2018
2 Reads

Diffraction efficiency performance of random anti-reflecting subwavelength surface structures on prefabricated fused silica binary gratings.

Appl Opt 2018 Jun;57(16):4421-4427

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. Read More

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June 2018
1 Read

Experiment on the temporal evolution characteristics of a CCD multilayer structure irradiated by a 1.06  μm continuous laser.

Appl Opt 2018 Jun;57(16):4415-4420

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. Read More

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June 2018
1 Read

Analysis of the optical center position of an optical system of a camera lens.

Appl Opt 2018 Jun;57(16):4409-4414

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. Read More

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June 2018
2 Reads

Simultaneous sum-frequency and second-harmonic generation in a planar waveguide.

Appl Opt 2018 Jun;57(16):4402-4408

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. Read More

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June 2018
1 Read

Evaluation of the PMMA microlens efficiency for the realization of a solar micro-concentrator array.

Appl Opt 2018 Jun;57(16):4396-4401

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. Read More

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June 2018
1 Read

High-efficiency directional backlight design for an automotive display.

Appl Opt 2018 Jun;57(16):4386-4395

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. Read More

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June 2018
1 Read

Experimental investigation on a nonuniformly correlated partially coherent laser.

Appl Opt 2018 Jun;57(16):4381-4385

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. Read More

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June 2018
1 Read

Fabrication of chirped and tilted fiber Bragg gratings on large-mode-area doubled-cladding fibers by phase-mask technique.

Appl Opt 2018 Jun;57(16):4376-4380

We demonstrate here the inscription of chirped and tilted fiber Bragg gratings (CTFBGs), to the best of our knowledge, for the first time in hydrogen-loaded large-mode-area (LMA) double-cladding fibers using UV pulses and linearly chirped phase masks. High reflectivity wideband adjustable band-rejection filters are achieved in fibers like LMA-GDF-10/130-M and PS-GDF-20/400-M, with a wavelength coverage of more than 10 nm and suppression ratio around 20 dB. The spectrum and temperature properties are investigated. Read More

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June 2018
1 Read

Tunable multiband plasmonic response of indium antimonide touching microrings in the terahertz range.

Appl Opt 2018 Jun;57(16):4368-4375

In this paper, we propose a terahertz (THz) plasmonic structure that supports three resonance modes, including the charge transfer plasmon (CTP), the bonding dipole-dipole plasmon, and the antibonding dipole-dipole plasmon, which can be strongly tuned by geometrical parameters, passively, and the temperature, actively. The structure exhibits a considerable thermal sensitivity of more than 0.01 THz/K. Read More

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June 2018
1 Read

Lock-in technique for extraction of pulse rates and associated confidence levels from video.

Appl Opt 2018 Jun;57(16):4360-4367

We investigate the practical applicability of video photoplethysmography (VPPG) to extract heart rates of subjects using noncontact color video recordings of human faces collected under typical indoor laboratory conditions using commercial video cameras. Videos were processed following three previously described simple VPPG algorithms to produce a time-varying plethysmographic signal. These time signals were then analyzed using, to the best of our knowledge, a novel, lock-in algorithm that was developed to extract the pulsatile frequency component. Read More

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June 2018
1 Read

Optical parameters of human blood plasma, collagen, and calfskin based on the Stokes-Mueller technique.

Appl Opt 2018 Jun;57(16):4353-4359

A decoupled analytical technique based on the Stokes-Mueller matrix decomposition method extracts polarization properties of human blood plasma, collagen solution, and calfskin. The proposed method is applied initially to extract the nine effective optical parameters of human blood plasma samples containing D-glucose powder with concentrations ranging from 0-1 M. The optical rotation angle of circular birefringence (CB) increases linearly with the glucose concentration in human blood plasma samples (r=0. Read More

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June 2018
1 Read

Bessel beam generation using a segmented deformable mirror.

Appl Opt 2018 Jun;57(16):4677-4682

Bessel beams with tunable spot size are desirable for many applications such as laser material processing, optical trapping, and imaging. In this paper, we report experimental and simulation results of using a segmented deformable mirror to generate zero- and higher-order Bessel beams that have a controllable transverse and longitudinal shape. The tilt angle and piston position of the mirror segments are optimized to recreate the phase structure of a reflective axicon. Read More

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June 2018
1 Read

Spectral refractive index technique for monitoring the beer mashing process.

Appl Opt 2018 Jun;57(16):4672-4676

During beer production, the mashing process is fundamental for extraction of the main sugars from the starch. The quantification of these fermentable sugars during the process provides a measure of the alcoholic content of the final beer. Therefore, monitoring of the sugar composition during beer production is very important for obtaining a quality product. Read More

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June 2018
1 Read

Photometric optimization and comparison of hybrid white LEDs for mesopic road lighting.

Appl Opt 2018 Jun;57(16):4665-4671

The photometric model for the mesopic luminous efficacy (LE) of hybrid white LEDs, including the radiant efficiency of both blue and red LEDs as well as the overall quantum efficiency of the phosphor layer or the quantum dot (QD) film, was developed. The optimal spectral parameters of integrated with quantum dots (QD-WLED), phosphor-converted white LED (pc-WLED) with red LEDs instead of red phosphor (pc/R WLED) for both color fidelity index (R) and color rendering index (R) above 70, 80, and 90 at correlated color temperatures of 2700-6500 K were obtained by maximizing the average LE of four road lighting standards. By comparing among pc-WLED, QD-WLED, and pc/R WLED, it was suggested that the pc/R WLEDs make strong candidates for mesopic road lighting. Read More

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June 2018
1 Read

Water surface-clutter suppression method based on infrared polarization information.

Appl Opt 2018 Jun;57(16):4649-4658

Targeting star-like water surface clutter, a clutter suppression method based on infrared polarization information is proposed. First, the clutter is suppressed from a global perspective using infrared polarization imaging technology, and a basic clutter-suppressed image is obtained. Then, using the Reed-Xiaoli anomaly detection algorithm, the remaining clutter positions in the basic image are determined from the polarization intensity image and basic image. Read More

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June 2018
1 Read

Optical design of low-cost polarimetric back-scatter sondes.

Authors:
Murray Hamilton

Appl Opt 2018 Jun;57(16):4639-4648

The optical design of a simple low-cost polarimetric balloon-borne backscatter sonde for detecting cloud thermodynamic phase is described. Simulations are performed to determine the best choice of polarization as well as the layout of the detectors with respect to the emitter. The variety of scattering angles of the detected photons, due to finite size detectors, has at least as great an effect as multiple scattering in determining the ratio of cross-polarized to co-polarized signal. Read More

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June 2018
1 Read

Composited holograms for the generation of cylindrical optical lattices and flower modes.

Appl Opt 2018 Jun;57(16):4633-4638

We present composited holograms to realize the azimuthal interference of cylindrical optical lattices (COLs) and the flower modes (FMs) of Fourier transform-truncated Bessel beams (FT-TBB). Three types of binarization operations are evaluated for the composited holograms generated by two FT-TBB with independent topological charges l and l and the same radial index p=1. Both the numerical solutions and experimental results demonstrate that the four types of COLs and FMs, namely, the conventional COL, interleaved COL, flower-core FM, and polygon-core FM, can be produced by the Fourier transformation of the composited holograms with the same radial index p=1 and topological combinations ||l|-|l||<2, ||l|-|l||=2, ||l|-|l||=3, and ||l|-|l||=4, respectively. Read More

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June 2018
1 Read

Spatio-temporal analysis of glass volume processing using ultrashort laser pulses.

Appl Opt 2018 Jun;57(16):4618-4632

Ultrashort laser pulses allow for the in-volume processing of glass through non-linear absorption, resulting in permanent material changes and the generation of internal stress. Across the manifold potential applications of this technology, process optimization requires a detailed understanding of the laser-matter interaction. Of particular relevance are the deposition of energy inside the material and the subsequent relaxation processes. Read More

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June 2018
1 Read

Transmission-enabled fiber Fabry-Perot cavity based on a deeply etched slotted micromirror.

Appl Opt 2018 Jun;57(16):4610-4617

In this work, we report the analysis, fabrication, and characterization of an optical cavity built using a Bragg-coated fiber (BCF) mirror and a metal-coated microelectromechanical systems (MEMS) slotted micromirror, where the latter allows transmission output from the cavity. Theoretical modeling, using Fourier optics analysis for the cavity response based on tracing the propagation of light back and forth between the mirrors, is presented. Detailed simulation analysis is carried out for the spectral response of the cavity under different design conditions. Read More

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June 2018
1 Read

Determining the size and refractive index of homogeneous spherical aerosol particles using Mie resonance spectroscopy.

Appl Opt 2018 Jun;57(16):4601-4609

Methods for determining the size and refractive index of single, homogeneous, micrometer-sized aerosol particles using Mie resonance spectroscopy are studied using measurements from optically trapped particles and light-scattering calculations based on Mie theory. We consider both single-particle broadband light scattering and cavity-enhanced Raman scattering (CERS) and demonstrate that, when resonances observed in either type of spectroscopy are fitted using Mie theory, the accuracy of the best fits are similar. However, broadband measurements can yield more resonances than CERS, thus reducing the uncertainty in the retrieved parameters of best fit and increasing the range of particles that can be characterized. Read More

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June 2018
1 Read

Direct bleaching of a Cr:YAG saturable absorber in a passively Q-switched Nd:YAG laser.

Appl Opt 2018 Jun;57(16):4595-4600

In this work, the anisotropy of nonlinear absorption in a crystal Q-switch was considered when we established coupled rate equations of a passively Q-switched laser. A [100]-cut Cr:YAG crystal, with initial transmission T=40%, was used as the Q-switch to evaluate the theoretical model, and the results of the simulation were in good accordance with the experiment. In order to control timing jitter of the passively Q-switched laser, an actively Q-switched Nd:YAG laser was applied to directly bleach the [100]-cut Cr:YAG crystal. Read More

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June 2018
1 Read

Rapid scanning optical delay line based on a diffraction grating pair for a low-coherence reflectometer.

Appl Opt 2018 Jun;57(16):4542-4550

We present a simple low-coherence time-domain interferometric reflectometer with a rapidly scanning optical delay line (RSODL) based on a non-parallel diffraction grating (DG) pair. The novelty of the solution is that the lightwave in the reference channel is focused on a galvo-mirror in a sub-mm static spot, which allows implementation of fast microelectromechanical systems scan optics. It is shown that the DG pair can be operated as a non-dispersive element that provides dynamic group delay of a reference lightwave. Read More

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June 2018
2 Reads

Sky brightness and color measurements during the 21 August 2017 total solar eclipse.

Appl Opt 2018 Jun;57(16):4590-4594

The sky brightness was measured during the partial phases and during totality of the 21 August 2017 total solar eclipse. A tracking CCD camera with color filters and a wide-angle lens allowed measurements across a wide field of view, recording images every 10 s. The partially and totally eclipsed Sun was kept behind an occulting disk attached to the camera, allowing direct brightness measurements from 1. Read More

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June 2018
1 Read

Generating flat-top beams with extended depth of focus.

Appl Opt 2018 Jun;57(16):4583-4589

Two approaches for generating flat-top beams (uniform intensity profile) with extended depth of focus are presented. One involves two diffractive optical elements (DOEs) and the other only a single DOE. The results indicate that the depth of focus of such beams strongly depends on the phase distribution at the output of the DOEs. Read More

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June 2018
1 Read

Iterative calibration of a multiview 3D display with linear extrinsic crosstalk using camera feedback.

Appl Opt 2018 Jun;57(16):4576-4582

In this paper, we propose a multiview 3D display calibration algorithm that compensates for misalignment between constituent layers. To minimize distortion of the 3D image due to misalignment, we employ an iterative algorithm using camera feedback. We first establish a mathematical model for the multiview display and predict distortion of a test image pattern due to misalignment. Read More

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June 2018
3 Reads

40  km amplifier-less transmission of single wavelength 90  Gbps four-level pulse amplitude modulation signals enabled by an ultrabroadband directly modulated laser.

Appl Opt 2018 Jun;57(16):4570-4575

An ultrabroadband, high linearity directly modulated laser (DML) module operated at the O-band is proposed. The effect of the package network on the DML module is first investigated. In the package network, a wire bonding compensation method is used to improve the resonance at high frequency, which can be equivalent to the channel equalization technique. Read More

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June 2018
2 Reads

High-speed computer-generated hologram based on resource optimization for block-based parallel processing: publisher's note.

Appl Opt 2018 Jun;57(16):4569

This publisher's note corrects the author affiliations in Appl. Opt.57, 3511 (2018)APOPAI0003-693510. Read More

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June 2018
2 Reads

Application of Fresnel diffraction to fabrication and characterization of glass phase steps.

Authors:
Ali Mahmoudi

Appl Opt 2018 Jun;57(16):4558-4562

In this paper we used Fresnel diffraction in order to study the effects of hydrofluoric acid concentration and temperature on glass etching rate. The technique is very simple and accurate, and nanoscale change of the glass thickness can be detected and measured during etching. Using measured etching rates we have fabricated several glass phase steps. Read More

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June 2018
1 Read

Comparative study on fractal analysis of interferometry images with application to tear film surface quality assessment.

Appl Opt 2018 Jun;57(16):4491-4498

The purpose of this research was to evaluate the applicability of the fractal dimension (FD) estimators to assess lateral shearing interferometric (LSI) measurements of tear film surface quality. Retrospective recordings of tear film measured with LSI were used: 69 from healthy subjects and 41 from patients diagnosed with dry eye syndrome. Five surface quality descriptors were considered, four based on FD and a previously reported descriptor operating in a spatial frequency domain (M), presenting temporal kinetics of post-blink tear film. Read More

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June 2018
3 Reads

Broadband laser-tuned whispering gallery mode in a micro-structured fiber embedded with iron oxide nanoparticles.

Appl Opt 2018 Jun;57(16):4563-4568

A grapefruit microstructured fiber-based resonator embedded with iron oxide nanoparticles is demonstrated in this paper. Due to efficient photon-to-heat conversion and transfer of the magnetic nanoparticles, such a device possesses broadband all-optical wavelength tuning with high sensitivity. Experimental results show that the tuning range and sensitivity can be up to ∼5. Read More

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June 2018
1 Read

Time series modeling of the ring laser gyroscope's bias considering the temperature delay effect.

Appl Opt 2018 Jun;57(16):4551-4557

Due to the temperature delay effect, the coefficients of the traditional ring laser gyroscope's (RLG) bias temperature model usually change with environmental temperature. In order to improve the applicability of the temperature model in complex temperature-varying environments, a modified RLG bias modeling method based on the temperature delay effect is proposed. The time series model (TSM), whose coefficients are independent of the environmental temperature variation, is established through theoretical analysis according to the temperature delay effect. Read More

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June 2018
1 Read

Relaxation oscillation suppressed, narrow linewidth, high beam quality, 1319  nm long-pulsed duration laser.

Appl Opt 2018 Jun;57(16):4692-4695

We first report a 1319 nm long-pulsed duration laser with relaxation oscillation suppressed by placing lithium triborate crystals into the laser cavity. Two more etalons were added into the laser cavity to further increase the difference in cavity loss between oscillating and non-oscillating modes. With very little reduction in average output laser power, the smooth temporal profile laser pulse was obtained with a pulse duration of 150 μs. Read More

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June 2018
1 Read

Freeform imaging spectrometer design using a point-by-point design method.

Appl Opt 2018 Jun;57(16):4718-4727

In this paper, we present a novel design method of freeform imaging spectrometers. All the freeform surfaces including the grating surface are generated point-by-point. The rays coming from multiple wavelengths, multiple fields, and different pupil coordinates are all used, and the refraction/reflection as well as the diffraction of the grating are considered simultaneously in the design process. Read More

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June 2018
1 Read

Theoretical large positive and negative lateral beam shift of the metal cladding waveguide in the mid-infrared region.

Appl Opt 2018 Jun;57(16):4714-4717

A large negative and positive lateral beam shift is presented in the midinfrared region based on the penetration enhancement effect of the ultrahigh order modes in the metal-cladding waveguide. The characteristics of the lateral beam shift have been discussed in theory, and the performance of the ultrahigh order modes is confirmed in an experiment at 5.4 µm. Read More

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June 2018
2 Reads

Rb vapor-cell clock demonstration with a frequency-doubled telecom laser.

Appl Opt 2018 Jun;57(16):4707-4713

We employ a recently developed laser system, based on a low-noise telecom laser emitting around 1.56 μm, to evaluate its impact on the performance of an Rb vapor-cell clock in a continuous-wave double-resonance scheme. The achieved short-term clock instability below 2. Read More

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June 2018
1 Read

Directional coupler based on an elliptic cylindrical nanowire hybrid plasmonic waveguide.

Appl Opt 2018 Jun;57(16):4701-4706

We present what we believe is a novel directional coupler based on an elliptic cylindrical nanowire hybrid plasmonic waveguide. Using the finite element method, the electric field distributions of y-polarized symmetric and antisymmetric modes of the coupler are compared, and the coupling and transmission characteristics are analyzed; then the optimized separation distance between the two parallel waveguides, 100 nm, is obtained. This optimized architecture fits in the weak coupling regime. Read More

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June 2018
1 Read

Multi-channel optical fiber refractometer based on tree topology structure.

Appl Opt 2018 Jun;57(16):4696-4700

A multi-channel optical fiber refractometer based on S fiber taper (SFT) cascaded with fiber Bragg grating (FBG) is proposed and experimentally demonstrated. The compact SFT acts as an in-line Mach-Zehnder interferometer (MZI) to be used as a band-pass filter (BPF) to tailor the FBG reflection, whose transmission spectrum is sensitive to the surrounding refractive index (SRI). Thus, the peak power of the FBG reflection is modulated by the SRI. Read More

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June 2018
1 Read