48,839 results match your criteria Applied optics[Journal]


Supervised spatio-spectral classification of fused images using superpixels.

Appl Opt 2019 Mar;58(7):B9-B18

The low spatial resolution of hyperspectral (HS) images generally limits the classification accuracy. Therefore, different multiresolution data fusion techniques have been proposed in the literature. In this paper, a method for supervised classification of spectral images from data fusion measurements is proposed. Read More

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http://dx.doi.org/10.1364/AO.58.0000B9DOI Listing

Computational requirements for real-time ptychographic image reconstruction.

Appl Opt 2019 Mar;58(7):B19-B27

Ptychographic imaging techniques can be coupled with tomographic image reconstruction techniques to obtain cross-sectional 3D images with resolution on the nanometer scale. However, such ptychographic x-ray computed tomography (PXCT) techniques require the collection of a large number of diffraction patterns. This work derives a set of equations that can be used to calculate the rate at which data can be collected given an experimental setup. Read More

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http://dx.doi.org/10.1364/AO.58.000B19DOI Listing

Wollaston prism-based structured illumination microscope with tunable frequency.

Appl Opt 2019 Mar;58(7):B1-B8

This work proposes an alternative structured illumination (SI) system based on a Wollaston prism (WP) illuminated by the diffracted field of an incoherent linear source. The proposed WP-based SI system presents several advantages. First, the generated fringes can be approximated by a pure sinusoidal pattern; thereby, computational methods developed for sinusoidal SI can be used without the need for additional processing. Read More

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http://dx.doi.org/10.1364/AO.58.0000B1DOI Listing
March 2019
2 Reads

Golden anniversary of Fourier optics: guest editorial.

Authors:
Edmund Y Lam

Appl Opt 2019 Mar;58(7):ED1-ED2

In 1968, Professor Joseph W. Goodman published the first edition of Introduction to Fourier Optics, which also laid the foundation of this field. For half a century, the book has been the definitive teaching and reference text, well known in particular for its clear and insightful writing. Read More

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http://dx.doi.org/10.1364/AO.58.000ED1DOI Listing

Prediction of lifetime by lumen degradation and color shift for LED lamps, in a non-accelerated reliability test over 20,000  h.

Appl Opt 2019 Mar;58(7):1855-1861

Although the predicted lifetime of the classical 6000 h test given by Energy Star is taken as the normal lifetime of LED products in most research and applications, the aim of this study is to explore the error in lifetime prediction of LED lamps based on the 6000 h test. A non-accelerated aging test with 10 LED lamps is conducted for 20,000 h (from March 2016 to now) under room temperature, which is long enough for this kind of lamp reaching the real lifetime with the normalized luminous flux dropping to 70% naturally. At different aging periods, the correspondent lifetime of each sample is predicted by the lumen degradation, and the median lifetime τ of 10 samples is obtained by applying the Weibull distribution. Read More

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http://dx.doi.org/10.1364/AO.58.001855DOI Listing
March 2019
2 Reads

Phase-shifting interferometry-based Fourier transform channeled spectropolarimeter.

Appl Opt 2019 Mar;58(7):1830-1840

Channeled spectropolarimetry is a snapshot technique for measuring the spectral dependence of the state of polarization of light. However, it suffers from two major limitations, namely, its high sensitivity to environmental perturbations and its susceptibility to channel crosstalk. These limitations reduce the polarimetric reconstruction accuracy of the spectropolarimeter. Read More

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http://dx.doi.org/10.1364/AO.58.001830DOI Listing
March 2019
1 Read

Computational optical sensing and imaging: introduction.

Appl Opt 2019 Mar;58(7):COS1-COS2

The OSA Topical Meeting on Computational Optical Sensing and Imaging (COSI) was held June 25-June 28, 2018 in Orlando, Florida, USA, as part of the Imaging and Applied Optics Congress. In this feature issue, we present several papers that cover the techniques, topics, and advancements in the field presented at the COSI meeting highlighting the integration of opto-electric measurement and computational processing. Read More

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http://dx.doi.org/10.1364/AO.58.00COS1DOI Listing

Self-referenced technology for refractive index measurement under mechanical vibration and temperature fluctuation.

Appl Opt 2019 Mar;58(7):1862-1867

A novel critical angle refractometer with self-referenced performance (SRCAR) under mechanical vibration and temperature fluctuation is presented. In a traditional CAR, mechanical vibrations and temperature fluctuations always exist and cause errors. To reduce these errors, a CAR is redesigned by introducing a reference glass with a known refractive index so that an exact calibration curve can always be determined, even though intense mechanical vibrations exist. Read More

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http://dx.doi.org/10.1364/AO.58.001862DOI Listing
March 2019
1 Read

Influence of asymmetric grating structures on measurement accuracy in integrated phase grating interference-based metrology.

Appl Opt 2019 Mar;58(7):1847-1854

We present an analysis of the position error caused by asymmetry in phase grating measurement systems, demonstrating that such error is dependent on the structure of the grating and the measurement order. The asymmetry-induced error varies as a function of diffraction order, with the nature of this variation depending on the grating structure. We verify our analysis by comparing the average error obtained with a multiorder interferometer to the error simulated using an atomic force microscopy scanning profile. Read More

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https://www.osapublishing.org/abstract.cfm?URI=ao-58-7-1847
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http://dx.doi.org/10.1364/AO.58.001847DOI Listing
March 2019
16 Reads

Method for measuring the resonant absorption coefficient of rare-earth-doped optical fibers.

Appl Opt 2019 Mar;58(7):1841-1846

A nondestructive method for measuring the resonant absorption coefficient of rare-earth-doped optical fibers is introduced. It can be applied to a broad range of fiber designs and host materials. The method compares the side-collected spontaneous emission at two arbitrary locations along the fiber as a function of the pump wavelength to extract the absorption coefficient. Read More

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http://dx.doi.org/10.1364/AO.58.001841DOI Listing

Surface plasmon resonance biosensor based on graphene and grating excitation.

Appl Opt 2019 Mar;58(7):1824-1829

A surface plasmon resonance biosensor based on a graphene-decorated grating excitation structure is proposed in this paper. The biosensor consists of a three-layer structure, including a graphene layer, a grating layer, and a high refractive index layer. The material of the grating layer is silica. Read More

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http://dx.doi.org/10.1364/AO.58.001824DOI Listing

Polarization dependence of a graphene-optical fiber hybrid Mach-Zehnder interferometer.

Appl Opt 2019 Mar;58(7):1808-1812

Graphene exhibits a particular optical polarization dependence property, which is that supporting optical polarization states of graphene can be readily altered through tuning the polarity of the imaginary part of its conductivity. The in-fiber Mach-Zehnder interferometer (MZI) possesses extremely high sensitivity to the surrounding refractive index through cladding modes. Combining graphene and the in-fiber interferometer, a graphene-optical fiber hybrid MZI is constructed. Read More

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http://dx.doi.org/10.1364/AO.58.001808DOI Listing
March 2019
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Vignetted-aperture correction for spectral cameras with integrated thin-film Fabry-Perot filters.

Appl Opt 2019 Mar;58(7):1789-1799

Spectral cameras with integrated thin-film Fabry-Perot filters have become increasingly important in many applications. These applications often require the detection of spectral features at specific wavelengths or to quantify small variations in the spectrum. This can be challenging since thin-film filters are sensitive to the angle of incidence of the light. Read More

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http://dx.doi.org/10.1364/AO.58.001789DOI Listing

Pattern recognition system based on photoanisotropic copies.

Appl Opt 2019 Mar;58(7):1778-1788

In this paper, we present a method of pattern recognition based on obtaining the photoanisotropic copies of object images. Such copies are induced on the dynamic polarization-sensitive material when the amplitude image of the object formed by a spatial light modulator is transilluminated by linearly polarized light with a wavelength actinic for the used material. In this case, the distribution of the intensities over the amplitude image is converted into the distribution of photoanisotropy over the sample of a polarization-sensitive material. Read More

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http://dx.doi.org/10.1364/AO.58.001778DOI Listing

Parabolic-cylinder-like long-period fiber grating sensor based on refractive index modulation enhancement effect.

Appl Opt 2019 Mar;58(7):1772-1777

A parabolic-cylinder-like long-period fiber grating (PCL-LPFG) is designed and experimentally fabricated successfully by a CO laser for the first time, to the best of our knowledge. The PCL-LPFG consists of an array of nonplanar PCL-shaped grids. The theoretical model of the PCL-LPFG shows that the PCL grid enables enhancement of the refractive index (RI) modulation efficiency and changes the mode coupling characteristics. Read More

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http://dx.doi.org/10.1364/AO.58.001772DOI Listing
March 2019
1 Read

General silicon-on-insulator higher-order mode converter based on substrip dielectric waveguides.

Appl Opt 2019 Mar;58(7):1763-1771

A general silicon mode-converter waveguide that converts a fundamental mode to any higher-order mode is proposed. Specifically, dielectric substrip waveguides are inserted in the fundamental mode propagation path so that the conversion is done directly in the same propagation waveguide, without coupling the power into another waveguide as it happens in traditional mode converters. The device has a very small footprint compared to traditional converters. Read More

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http://dx.doi.org/10.1364/AO.58.001763DOI Listing
March 2019
1.784 Impact Factor

Computational image speckle suppression using block matching and machine learning.

Appl Opt 2019 Mar;58(7):B39-B45

We develop an image despeckling method that combines nonlocal self-similarity filters with machine learning, which makes use of convolutional neural network (CNN) denoisers. It consists of three major steps: block matching, CNN despeckling, and group shrinkage. Through the use of block matching, we can take advantage of the similarity across image patches as a regularizer to augment the performance of data-driven denoising using a pre-trained network. Read More

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http://dx.doi.org/10.1364/AO.58.000B39DOI Listing

Image contrast enhancement method based on display and human visual system characteristics.

Appl Opt 2019 Mar;58(7):1813-1823

At the present time, there are many image contrast enhancement methods where the main considerations are detail enhancement, noise suppression, and high contrast suppression. Traditional methods ignore the characteristics of the display or merely consider the display as a whole. However, due to the limited dynamic range of most display devices on the market, the difference between two adjacent grayscales of the display is often below the just noticeable difference of the human visual systems, which causes many image details to be invisible on the display. Read More

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http://dx.doi.org/10.1364/AO.58.001813DOI Listing
March 2019
1.784 Impact Factor

Modified constellation reshaping method for PAPR reduction of PDM CO-OFDM based on a SLM algorithm.

Appl Opt 2019 Mar;58(7):1800-1807

In this paper, we propose a modified constellation reshaping method for peak-to-average power ratio (PAPR) reduction in polarization division multiplexing (PDM) coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems based on the selective mapping (SLM) method. A modified quadrature amplitude modulation (M-QAM) constellation is generated that has the same minimum distance as that of the conventional QAM (C-QAM) constellation. The M-SLM method is denoted as the M-QAM constellations combining with the traditional SLM method. Read More

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http://dx.doi.org/10.1364/AO.58.001800DOI Listing
March 2019
2 Reads

Bloch surface waves at the telecommunication wavelength with lithium niobate as the top layer for integrated optics.

Appl Opt 2019 Mar;58(7):1757-1762

Lithium niobate (LN)-based devices are widely used in integrated and nonlinear optics. This material is robust and resistive to high temperatures, which makes the LN-based devices stable, but challenging to fabricate. In this work, we report on the design, manufacturing, and characterization of engineered dielectric media with thin-film LN (TFLN) on top for the coupling and propagation of electromagnetic surface waves at telecommunication wavelengths. Read More

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http://dx.doi.org/10.1364/AO.58.001757DOI Listing
March 2019
2 Reads

Effects of end surface and angle coupling on mode splitting and suppression in a cylindrical microcavity.

Appl Opt 2019 Mar;58(7):1752-1756

A cylindrical microcavity conventionally has the characteristics of simple fabrication and high Q factor, where the rich physics of mode splitting and suppression caused by mode excitation, coupling, and interference have been realized for highly sensitive sensing and cavity quantum electrodynamics. In this paper, we show experimentally and theoretically a simple method to tailor these two mechanisms via near-end surface and angle coupling in a single-mode fiber cylindrical microcavity. Mode splitting can be enhanced due to the interference between localized and axial modes as the effect of near-end surface coupling, validated by the coupled-mode model. Read More

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http://dx.doi.org/10.1364/AO.58.001752DOI Listing

Self-beating resonant optical gyroscope with a "reflector": the possibility of high sensitivities at reduced costs.

Appl Opt 2019 Mar;58(7):1699-1706

Using simulations and theoretical analysis, we present an innovative readout technique that uses the change in a beat frequency signal for sensing rotation in the resonant fiber gyroscope with a "reflector." Unlike traditional fiber optic gyros, this gyroscope uses an embedded reflecting element that deliberately couples the clockwise and counter-clockwise propagating waves for sensing rotation. Our analytical results predict increased immunity to the degrading effects of backscattering, Kerr nonlinearities, and ambient variations at an optimum nonreciprocal bias. Read More

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http://dx.doi.org/10.1364/AO.58.001699DOI Listing

Tm-doped silica-glass fiber for ∼2-μm fiber laser.

Appl Opt 2019 Mar;58(7):1747-1751

Tm-doped silica-glass preforms were fabricated by the modified chemical vapor deposition process combined with the solution doping technique. Its spectroscopic properties were evaluated according to the detected absorption spectrum and the fluorescence spectrum. The calculated maximum emission cross section of Tm ions in this core glass is 5. Read More

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https://www.osapublishing.org/abstract.cfm?URI=ao-58-7-1747
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http://dx.doi.org/10.1364/AO.58.001747DOI Listing
March 2019
3 Reads
1.784 Impact Factor

Simultaneous measurement of phase transmission and linear or circular dichroism of an object under test.

Appl Opt 2019 Mar;58(7):1739-1746

This publication presents a novel interferometric method for the simultaneous spatially resolved analysis of an object under test regarding the phase transmission function and the magnitude and orientation of dichroism. Analogous to the classical phase-shifting interferometry, the measurement strategy is based on the variation of phase and polarization in an interferometer. This procedure allows one to analyze simultaneously and spatially resolved the dichroic properties of the object and its impact on the phase of the incoming light in one measurement cycle. Read More

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http://dx.doi.org/10.1364/AO.58.001739DOI Listing

Compact low-noise passively mode-locked Er-doped femtosecond all-fiber laser with 2.68  GHz fundamental repetition rate.

Appl Opt 2019 Mar;58(7):1733-1738

A passively mode-locked Er-doped fiber laser with a fundamental repetition rate of 2.68 GHz is reported. The oscillator operating at a central wavelength of 1558. Read More

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http://dx.doi.org/10.1364/AO.58.001733DOI Listing
March 2019
2 Reads

Enhanced left/right asymmetry in reflection and transmission due to a periodic multilayer of a topological insulator and an anisotropic dielectric material.

Appl Opt 2019 Mar;58(7):1724-1732

Very weak left/right asymmetry in reflection and transmission is offered by a layer of a topological insulator on top of a layer of an anisotropic dielectric material, but it can be enhanced very significantly by using a periodic multilayer of both types of materials. This is an attractive prospect for realizing one-way terahertz devices, because both types of materials can be grown using standard physical-vapor-deposition techniques. Read More

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http://dx.doi.org/10.1364/AO.58.001724DOI Listing

Lidar algorithms in 3D scanning for atmospheric layering and planetary boundary layer height retrieval: comparison with other techniques: publisher's note.

Appl Opt 2019 Mar;58(7):1723

This publisher's note amends the Funding section of Appl. Opt.57, 8199 (2018)APOPAI0003-693510. Read More

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http://dx.doi.org/10.1364/AO.58.001723DOI Listing
March 2019
1 Read

Numerical investigations of synchronization and communication based on an electro-optic phase chaos system with concealment of time delay.

Appl Opt 2019 Mar;58(7):1715-1722

A modified electro-optic phase chaos system that can conceal time delay (TD) and allows for unidirectional message transmission, is numerically investigated. The configuration includes two cascaded delay loops, and the parallel-coupled microresonators (PCMRs) in one of two loops result in a frequency-dependent group delay. The largest Lyapunov exponent (LLE), Lempel-Ziv complexity (LZC) and permutation entropy (PE) are used to distinguish the chaotic behavior and the degree of complexity in a time series, and the autocorrelation function (ACF) and the delayed mutual information (DMI) are plotted to extract the TD. Read More

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http://dx.doi.org/10.1364/AO.58.001715DOI Listing

Coupling efficiency of light intensity from the blackbody cavity into a cone-shaped optical fiber.

Appl Opt 2019 Mar;58(7):1707-1714

High-temperature blackbody radiation can provide the light source for broadband fiber sensing systems. To improve coupling efficiency, a coupling model of light intensity from the blackbody cavity into a cone-shaped optical fiber was proposed. Influence of parameters of cone-shaped fiber and the blackbody cavity on coupling efficiency of light intensity were analyzed. Read More

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http://dx.doi.org/10.1364/AO.58.001707DOI Listing
March 2019
1 Read
1.784 Impact Factor

Dual-wavelength terahertz sensing based on anisotropic Fano resonance metamaterials.

Appl Opt 2019 Mar;58(7):1667-1674

Higher order Fano resonance metamaterials provide a desirable platform for biosensing applications. In this work we exhibit higher order Fano modes by designing an elliptical metallic ring. The simulation results show that for Fano resonant metamaterials, the higher order modes lead to improved sensitivity to refractive index change and larger frequency shifts. Read More

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http://dx.doi.org/10.1364/AO.58.001667DOI Listing

Advances and challenges of soft contact lens design for myopia control.

Appl Opt 2019 Mar;58(7):1639-1656

Myopia has shown a rapid increase during the past decades around the world, posing great threat to ocular health. Myopia is mostly attributed to an overgrowth of the axial length of the eye, which is an abnormal growth of the sclera that is attributed to a series of environmental and genetic factors and their interactions. Soft contact lenses have the potential to be an ideal method of correction for slowing myopic progression. Read More

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https://www.osapublishing.org/abstract.cfm?URI=ao-58-7-1639
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http://dx.doi.org/10.1364/AO.58.001639DOI Listing
March 2019
6 Reads

Shifting colored coded aperture design for spectral imaging.

Appl Opt 2019 Mar;58(7):B28-B38

Compressive spectral imaging (CSI) systems sense 3D spatio-spectral data cubes with just a few two-dimensional (2D) projections by using a coded aperture, a dispersive element, and a focal plane array (FPA). The coded apertures in these systems, whose main function is the modulation of the data cube, are often implemented through photomasks attached to piezoelectric devices. A remarkable improvement on this configuration has been recently proposed, the replacement of the block-unblock coded apertures by patterned optical filter arrays, referred to as "colored" coded apertures, which allow spatial and spectral modulation. Read More

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http://dx.doi.org/10.1364/AO.58.000B28DOI Listing

Performance analysis of the infrared imaging system for aircraft plume detection from geostationary orbit.

Appl Opt 2019 Mar;58(7):1691-1698

In view of the optical detection requirements of wide-area and continuous surveillance of air targets, the detection ability of an infrared imaging system in geostationary orbit for aircraft plumes is studied. The point spread model of the subpixel imaging of the full chain, including the aircraft plume, the sea surface, the environmental atmosphere, the optical system, and the imaging detector is established. The detection ability of the typical imaging system in geostationary orbit is analyzed from the signal-to-noise ratio (SNR) and the detection range in combination with the effect of the point spread function (PSF) of the optical system. Read More

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http://dx.doi.org/10.1364/AO.58.001691DOI Listing

Enhancement of electric and magnetic dipole transition of rare-earth-doped thin films tailored by high-index dielectric nanostructures.

Appl Opt 2019 Mar;58(7):1682-1690

We propose a simple experimental technique to separately map the emission from electric and magnetic dipole transitions close to single dielectric nanostructures, using a few-nanometer thin film of rare-earth-ion-doped clusters. Rare-earth ions provide electric and magnetic dipole transitions of similar magnitude. By recording the photoluminescence from the deposited layer excited by a focused laser beam, we are able to simultaneously map the electric and magnetic emission enhancement on individual nanostructures. Read More

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http://dx.doi.org/10.1364/AO.58.001682DOI Listing

Design of a head-up display based on freeform reflective systems for automotive applications.

Appl Opt 2019 Mar;58(7):1675-1681

Automotive head-up display (HUD), a typical application in augmented reality (AR), has gained popularity in recent years. In this paper, we propose a novel design configuration of freeform off-axis three-mirror systems for automotive head-up display (HUD) application. In the configuration, the image source, the flat mirror, and the freeform mirror are allocated on the same horizontal level to guarantee a compact structure as well as to make the optical elements easy to be assembled. Read More

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https://www.osapublishing.org/abstract.cfm?URI=ao-58-7-1675
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http://dx.doi.org/10.1364/AO.58.001675DOI Listing
March 2019
5 Reads

Fiber-optic Fabry-Perot pressure sensor based on sapphire direct bonding for high-temperature applications.

Appl Opt 2019 Mar;58(7):1662-1666

In this study, a fiber-optic Fabry-Perot (FP) high-temperature pressure sensor based on sapphire direct bonding is proposed and experimentally demonstrated. The sensor is fabricated by direct bonding of two-layer sapphire wafers, including a pressure diaphragm wafer and a cavity-etched wafer. The sensor is composed of a sensor head that contains a vacuum-sealed cavity arranged as an FP cavity and a multimode optical fiber. Read More

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http://dx.doi.org/10.1364/AO.58.001662DOI Listing

Highly coherent, watt-level deep-UV radiation via a frequency-quadrupled Yb-fiber laser system.

Appl Opt 2019 Mar;58(7):1657-1661

We demonstrate a 1.4 W continuous-wave (CW) laser at 243.1 nm. Read More

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http://dx.doi.org/10.1364/AO.58.001657DOI Listing

Rapid identification of rice species by laser-induced breakdown spectroscopy combined with pattern recognition.

Appl Opt 2019 Mar;58(7):1631-1638

Laser-induced breakdown spectroscopy (LIBS) combined with pattern recognition was proposed to discriminate rice species. LIBS spectra in the range of 210-480 nm wavelength from 11 different rice species were collected and preprocessed. Principal component analysis was applied to extract the characteristic variables from LIBS spectral data. Read More

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http://dx.doi.org/10.1364/AO.58.001631DOI Listing

Turbine blade temperature error as measured with an optical pyrometer under different wavelengths and blade TBC thickness.

Appl Opt 2019 Mar;58(7):1626-1630

The optical pyrometer is a widely used instrument for measuring the temperature of gas turbine blade targets. However, one of the limitations of this instrument is the measurement error caused by reflected radiation from the high-temperature surrounding environment. This paper presents an analysis of such measurement error with consideration of a wavelength detection range of 2. Read More

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http://dx.doi.org/10.1364/AO.58.001626DOI Listing

Bismuth quantum dots as an optical saturable absorber for a 1.3  μm Q-switched solid-state laser.

Appl Opt 2019 Mar;58(7):1621-1625

Two-dimensional bismuth has attracted extensive attention for its unique properties, such as a moderate bandgap, high carrier mobility, and high stability. In this work, a uniform bismuth quantum dots saturable absorber (BiQDs-SA) was successfully fabricated by the liquid-phase exfoliation method. It was successfully employed in a passively Q-switched bulk laser operating at the telecommunication wavelength of 1. Read More

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http://dx.doi.org/10.1364/AO.58.001621DOI Listing

Dual-channel inline coherent imaging.

Appl Opt 2019 Mar;58(7):1614-1620

We present a dual-channel inline coherent imaging system for laser machining monitoring using a single spectrometer. Sensitivity enhancement due to the added signal of the two input channels is demonstrated with a maximum sensitivity of 99 dB at a 73 kHz acquisition rate. We also treat, theoretically and experimentally, dual-channel detection in the case of signal saturation. Read More

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http://dx.doi.org/10.1364/AO.58.001614DOI Listing

Image-guided vibrometry system integrated with spectral- and time-domain optical coherence tomography.

Appl Opt 2019 Mar;58(7):1606-1613

Vibrometry using optical coherence tomography (OCT) can provide valuable information for investigating either the mechanical properties or the physiological function of biological tissues, especially the hearing organs. Real-time imaging of the measured tissues provides structure imaging and spatial guidance for and is thus highly demanded by such vibrometry. However, the traditional time-domain OCT (TD-OCT) systems, although capable of subnanometric vibrometry at large ranges of frequencies, are unable to offer an imaging speed that is high enough to acquire depth-resolved images for guidance. Read More

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http://dx.doi.org/10.1364/AO.58.001606DOI Listing
March 2019
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Reduction of non-uniformity for a 16  ×  16 arrayed waveguide grating router based on silica waveguides.

Appl Opt 2019 Feb;58(4):1139-1145

Here, a newly designed 16×16 cyclic arrayed waveguide grating router, capable of achieving loss uniformity across the whole free spectral range (FSR), is fabricated and experimentally demonstrated. This device is based on commonly used silica waveguides, which are compatible with basic planar lightwave circuit technology. The design, simulation, and experimental verification of the proposed method are presented, with the experimental results showing that the loss non-uniformity of FSR reduced from 2. Read More

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http://dx.doi.org/10.1364/AO.58.001139DOI Listing
February 2019

Homography based identification for automatic and robust calibration of projection integral imaging displays.

Appl Opt 2019 Feb;58(4):1200-1209

Recent advances in the creation of microlens arrays as holographic optical elements allow the creation of projector-based see-through light field displays suitable for augmented reality. These systems require an accurate calibration of the projector with relation to the microlens array, as any small misalignment causes the 3D reconstruction to fail. The methods reported so far require precise placement of the calibration camera w. Read More

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http://dx.doi.org/10.1364/AO.58.001200DOI Listing
February 2019

Symbol error rate of soft-decision multiple pulse position modulation over turbulent channels.

Authors:
Dima Bykhovsky

Appl Opt 2019 Feb;58(4):1193-1199

Soft-decision multiple-pulse-position modulation (MPPM) is one of the favored free-space optical communication modulations. This paper derives theoretical expressions for the symbol error rate of both fast and slow fading conditions applied for soft-decision MPPM without channel state information at the receiver as a particular case of nonmemoryless channel conditions. The theoretical expressions for lognormal and gamma-gamma modeled turbulence were successfully verified by simulation. Read More

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http://dx.doi.org/10.1364/AO.58.001193DOI Listing
February 2019

Broadband LP-LP mode converter for O-, E-, S-, C-, L-, and U-bands.

Appl Opt 2019 Feb;58(4):1185-1192

This paper proposes a novel all-optical fiber mode converter for mode conversion from LP to LP and vice versa. The mode converter is formed by connecting a single-mode fiber, a taper-core multi-mode fiber, and a few-mode fiber (FMF) together. The taper fiber core is designed to convert LP mode to LP. Read More

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http://dx.doi.org/10.1364/AO.58.001185DOI Listing
February 2019
1 Read

Field stabilization control of the European Extremely Large Telescope under wind disturbance.

Appl Opt 2019 Feb;58(4):1174-1184

This paper discusses the field stabilization control of the M5 unit under wind disturbances. The first part is a literature survey of the spectral content of the wind disturbance. Next, a simplified model of a tip/tilt mirror control system is used to analyze the conditions for control-structure interaction. Read More

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http://dx.doi.org/10.1364/AO.58.001174DOI Listing
February 2019
1 Read

Automatic morphological filtering algorithm for airborne lidar data in urban areas.

Appl Opt 2019 Feb;58(4):1164-1173

Filtering is a key step for most airborne lidar post-applications in urban areas. To solve the problems of complex parameter settings and low filtering accuracy in complicated urban environments, an automatic morphological filter was proposed. In this paper, the optimal maximum filtering window can be determined automatically by applying a series of morphological top-hat operations. Read More

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http://dx.doi.org/10.1364/AO.58.001164DOI Listing
February 2019
2 Reads
1.784 Impact Factor

External right-angle measurement using a two-autocollimator system.

Appl Opt 2019 Feb;58(4):1158-1163

We report on a non-contact method for external right-angle measurement using two autocollimators. A precise mathematical model is deduced to evaluate and deduct the measuring error. The values measured with our method are very coincident compared with the results measured by a ZYGO interferometer. Read More

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http://dx.doi.org/10.1364/AO.58.001158DOI Listing
February 2019

Broadband light absorption enhancement in randomly rotated elliptical nanohole arrays for photovoltaic application.

Appl Opt 2019 Feb;58(4):1152-1157

Semiconducting nanohole arrays have been considered as a promising candidate for high-efficiency solar cells. In this paper, the optical absorption property of randomly rotated elliptical nanohole arrays consisting of 1×1, 2×2, and 4×4 cells has been investigated. It is found that the average ultimate efficiency of the arrays increases with the increase of the size of the supercell. Read More

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http://dx.doi.org/10.1364/AO.58.001152DOI Listing
February 2019
3 Reads