53,581 results match your criteria Applied Optics[Journal]

Tunable depth of focus with modified complex amplitude modulation of an optical field.

Appl Opt 2022 Apr;61(12):3502-3509

Bessel beams have nondiffraction and self-healing properties in the propagation direction and are widely used in particle optical manipulation and optical microscopy. Bessel beams can be generated by axicons or spatial light modulators, which can produce a zero-order or high-order Bessel beam with different parameters depending on the specific application. The modulation of Bessel beams achieved in the spatial spectrum domain by optimization algorithms has a low light energy utilization rate due to the small effective modulation region. Read More

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Elliptically polarized sum-frequency generation by total-internal-reflection-based optical rotation quasi-phase-matching technique.

Appl Opt 2022 Apr;61(12):3494-3501

This work demonstrates the elliptically polarized radiation of sum-frequency generation by the total-internal-reflection-based optical rotation quasi-phase-matching technique that allows polarization rotation in the presence of an external electric field across a rectangular-shaped, -coated, MgO-doped crystal. This thin film is employed to control the phase shifts generated by - and -polarized light propagation at each bounce point of the slab-film interface. The computer-aided simulation yielded a high conversion efficiency of 7. Read More

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Scanning force sensing at micrometer distances from a conductive surface with nanospheres in an optical lattice.

Appl Opt 2022 Apr;61(12):3486-3493

The center-of-mass motion of optically trapped dielectric nanoparticles in a vacuum is extremely well decoupled from its environment, making a powerful tool for measurements of feeble subattonewton forces. We demonstrate a method to trap and maneuver nanoparticles in an optical standing wave potential formed by retroreflecting a laser beam from a metallic mirror surface. We can reliably position a ∼170 diameter silica nanoparticle at distances of a few hundred nanometers to tens of micrometers from the surface of a gold-coated silicon mirror by transferring it from a single-beam tweezer trap into the standing wave potential. Read More

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In situ areal mass measurement of laser shock-loaded aluminum using point-projection x-ray backlighting.

Appl Opt 2022 Apr;61(12):3480-3485

X-ray backlighting is been widely used today in dynamic phenomena observation. By applying proper synchronizing techniques, the in-situ data of the intensity distribution of the fragments in laser-driven shock-loaded aluminum were obtained for a particular moment using x-ray backlighting imaging. The image resolution was better than 40 µm in this context by introducing a pinhole. Read More

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Enhanced performance of a reservoir computing system based on a dual-loop optoelectronic oscillator.

Appl Opt 2022 Apr;61(12):3473-3479

Time-delayed reservoir computing (RC) is a brain inspired paradigm for processing temporal information, with simplification in the network's architecture using virtual nodes embedded in a temporal delay line. In this work, a novel, to the best of our knowledge, RC system based on a dual-loop optoelectronic oscillator is proposed to enhance the prediction and classification. The hardware is compact and easy to implement, and only a section of fiber compared to the traditional optoelectronic oscillator reservoir is added to conform the dual-loop scheme. Read More

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Robust Risley prism control based on disturbance observer for system line-of-sight stabilization.

Appl Opt 2022 Apr;61(12):3463-3472

In this paper, a robust control based on disturbance observer is proposed to improve the tracking accuracy of the Risley prism system (RPS). Applying the flexible thin-wall ring mechanism in the RPS causes a series of tracking and pointing challenges. Disturbances such as friction, shaft deformation, and model perturbation significantly deteriorate the tracking and pointing accuracy of the RPS. Read More

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Detection of captan residues in apple juice using fluorescence spectroscopy combined with a genetic algorithm and support vector machines.

Appl Opt 2022 Apr;61(12):3455-3462

The captan residues in apple juice were detected by fluorescence spectrometry, and the content level of captan was predicted based on a genetic algorithm and support vector machines (GA-SVMs). According to the captan concentration in apple juice, the experimental samples were divided into four levels, including no excess, slight excess, moderate excess, and severe excess. A GA was used to select the characteristic wavelength and optimize SVM parameters, and SVM was applied to train the classification model. Read More

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Long distance high resolution FMCW laser ranging with phase noise compensation and 2D signal processing.

Appl Opt 2022 Apr;61(12):3443-3454

A long distance high resolution frequency-modulated continuous wave (FMCW) laser rangefinder with phase noise compensation and two-dimensional (2D) data processing skills is developed. Range-finding ladar consists of a continuously chirped laser source, an auxiliary reference interferometer, and a monostatic optical transceiver for target illumination and return photon collection. To extend the range unambiguity and lower the electronic processing bandwidth, a two-step laser frequency chirping scheme is adopted, where a long pulse width, small frequency bandwidth laser chirping signal are used in step 1 for coarse distance estimation, and a short pulse width and large frequency bandwidth laser chirping signal are applied afterwards for step 2 high resolution distance realization. Read More

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Circular dichroic metasurface based on a "double L" structure.

Appl Opt 2022 Apr;61(12):3435-3442

Based on the theory of circular polarization dichroism in electromagnetic fields, this paper studies the circular dichroism (CD) characteristics of metasurfaces. Using a stable silicon material, an innovative "double L-shaped" composite structure formed by two L crosses is proposed to improve CD. Under a wide spectrum with wavelengths of 1000-1500 nm, the left circularly polarized (LCP) and right circularly polarized (RCP) lights pass through the structure, and we study the influence of different structural parameters on the CD, in order to obtain the best structural parameters. Read More

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Internal phase control of coherent fiber laser array without ambiguous phase based on double wavelength detection.

Appl Opt 2022 Apr;61(12):3429-3434

High-power fiber lasers have been widely utilized in manufacturing, medical care, and many other fields. Due to mode instability, nonlinear effects, and so on, the output power of a monolithic fiber laser is limited. Coherent beam combining (CBC) of fiber lasers is a promising way to obtain higher output power. Read More

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Nondestructive determination of SSC in an apple by using a portable near-infrared spectroscopy system.

Appl Opt 2022 Apr;61(12):3419-3428

The soluble solids content (SSC) is an important factor in the internal quality detection of apples. It is essential to have reliable and high-speed measurement of the SSC. However, almost all traditional equipment is inconvenient and expensive. Read More

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Annular illumination in 2D quantitative phase imaging: a systematic evaluation.

Appl Opt 2022 Apr;61(12):3409-3418

Quantitative phase imaging (QPI) is an invaluable microscopic technology for definitively imaging phase objects such as biological cells and optical fibers. Traditionally, the condenser lens in QPI produces disk illumination of the object. However, it has been realized by numerous investigators that annular illumination can produce higher-resolution images. Read More

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Incoherent broadband cavity-enhanced absorption spectroscopy for sensitive measurement of nutrients and microalgae.

Appl Opt 2022 Apr;61(12):3400-3408

Incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) can achieve sensitive measurements at trace concentrations for liquid phase marine samples. The IBBCEAS system consists of a cavity-enhancement module (CEM) and a transmission hyperspectral module (THM). The CEM has cavity-enhancement factors up to 78 at 550 nm. Read More

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Analysis of crosstalk in spectral beam combining of diode laser bar.

Appl Opt 2022 Apr;61(12):3390-3399

Spectral beam combining (SBC) of laser diodes has been proven to be an effective method to improve beam brightness. The crosstalk between different emitters in the SBC system will significantly affect the beam-combining efficiency and output beam properties without effective control. The interfering factors of the crosstalk beam intensity in semiconductor laser SBC have been theoretically analyzed, and experiments have been built to carry out the SBC of a semiconductor laser bar with a high filling factor of 80%. Read More

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Design of channeled spectropolarimeters.

Nathan Hagen

Appl Opt 2022 Apr;61(12):3381-3389

I present design and tolerancing guidelines for constructing channeled spectropolarimeter systems employing high-order retarders. The discussion includes how to select appropriate retarder thicknesses, how to accurately align the elements, how to tolerance the retarders, and how to analyze the effect of different polarizer types on the system performance. Read More

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Wideband, high spectral resolution UV convex grating imaging spectrometer based on an Offner structure.

Appl Opt 2022 Apr;61(12):3371-3380

Ultraviolet is an effective electromagnetic spectrum in material detection, which has wide application prospects in aerospace and environmental monitoring. A conventional imaging spectrometer has a narrow UV band and low spectral resolution. To solve this problem, a convex grating imaging spectrometer based on an Offner structure with F#2. Read More

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Super-resolution reconstruction of terahertz images based on a deep-learning network with a residual channel attention mechanism.

Appl Opt 2022 Apr;61(12):3363-3370

To date, the existing terahertz super-resolution reconstruction methods based on deep-learning networks have achieved noteworthy success. However, the terahertz image degradation process needs to fully consider the blur and noise of the high-frequency part of the image during the network training process, and cannot be replaced simply by interpolation, which has high complexity. The terahertz degradation model is systematically investigated, and effectively solves the above problems by introducing the remaining channel mechanism into the deep-learning network. Read More

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Maximum bandwidth of a composite achromatic quartz half-wave plate.

Appl Opt 2022 Apr;61(12):3357-3362

To investigate the characteristics of the achromatic bandwidth of composite achromatic quartz half-wave plates (QHWPs), three kinds of multi-element achromatic QHWPs with central wavelengths at 1000-3000 nm and relative deviation of the maximum phase retardation () of 1%-5% are discussed. Based on the particle swarm optimization algorithm, the maximum bandwidth of the composite achromatic QHWPs at room temperature is obtained. The results show that the achromatic bandwidth increases with . Read More

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Optomechanical design of a wide-field auroral imager on Fengyun-3D.

Appl Opt 2022 Apr;61(12):3349-3356

We present the optomechanical design and development of a wide-field auroral imager (WAI) on board the satellite Fengyun-3D. The optomechanical system of the WAI features a combination of a large field of view and a single-axis scanning mechanism. The combination makes the WAI perform better than its counterparts in temporal resolution in a low Earth orbit. Read More

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3D time-lapse imaging of a mouse embryo using intensity diffraction tomography embedded inside a deep learning framework.

Appl Opt 2022 Apr;61(12):3337-3348

We present a compact 3D diffractive microscope that can be inserted directly in a cell incubator for long-term observation of developing organisms. Our setup is particularly simple and robust, since it does not include any moving parts and is compatible with commercial cell culture containers. It has been designed to image large specimens (>100×100×100µ) with subcellular resolution. Read More

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Machine-learning reinforcement for optimizing multilayered thin films: applications in designing broadband antireflection coatings.

Appl Opt 2022 Apr;61(12):3328-3336

The design and fabrication of nanoscale multilayered thin films play an essential role in regulating the operation efficiency of sensitive optical sensors and filters. In this paper, we introduce a packaged tool that employs flexible electromagnetic calculation software with machine learning in order to find the optimized double-band antireflection coatings in intervals of wavelength from 3 to 5 µm and 8 to 12 µm. Instead of computing or modeling an extremely enormous set of thin film structures, this tool enhanced with machine learning can swiftly predict the optical properties of a given structure with >99. Read More

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Planar polishing process method based on real-time dressing of a polishing pad surface.

Appl Opt 2022 Apr;61(12):3319-3327

Planar polishing is an important manufacturing process for high-precision planar components. In this study, a real-time dresser and a planar polishing process based on real-time dressing for large-aperture optical plane components were developed. Efficient dressing of a polishing pad surface can be achieved with the real-time dresser. Read More

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Picosecond laser microwelding of AlSi-YAG for laser system assembly.

Appl Opt 2022 Apr;61(12):3312-3318

We report the successful picosecond laser welding of AlSi and YAG. This material combination is of significant interest to the field of laser design and construction. Parameter maps are presented that demonstrate the impact of pulse energy and focal position on the resultant weld. Read More

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UAV system with trinocular vision for external obstacle detection of transmission lines.

Appl Opt 2022 Apr;61(12):3297-3311

External obstacle detection is a significant task in transmission line inspection and is related to the safe operation of the power transmission grid. In recent years, unmanned aerial vehicles (UAVs) equipped with different devices have been widely used for transmission line inspection. However, because of the complex environment of transmission lines and weak power line textures in the obtained images, most existing methods and systems cannot meet the requirements for real-time and high-accuracy external obstacle detection of transmission lines. Read More

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Method of calculation of initial design parameters of microscope objective lenses with a long working distance.

Appl Opt 2022 Apr;61(12):3288-3296

We describe an analytic method of the initial design of microscope objectives with a long working distance. The optical system of a microscope objective is composed of two thin optical elements and a frontal optical element from several thick lenses. The paper describes formulas that make it possible to calculate fundamental parameters of the objective, namely Seidel aberration coefficients, radii of curvature, refractive indices of individual lenses of the microscope objective, etc. Read More

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Adaptive neuro fuzzy selection of important factors for prediction of plasmons in silver nanorods.

Appl Opt 2022 Apr;61(10):2864-2868

The major goal of this study was to find predictors of plasmon positions in silver nanorod (NR) optical absorption spectra. The goal of this study is to use an adaptive neural fuzzy inference system to identify the various input parameters for longitudinal surface plasmon resonance (LSPR) and transverse surface plasmon resonance (TSP). A seed strategy has been used for preparation of the silver NRs. Read More

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Underwater image restoration by red channel compensation and underwater median dark channel prior.

Appl Opt 2022 Apr;61(10):2915-2922

Underwater images often show low contrast, blurring, and color distortion due to the absorption and scattering of light. In contrast to existing underwater image restoration methods, we propose an underwater image restoration method with red channel compensation and blue-green channel restoration. First, a proposed approach relies on the hue and attenuation differences between different color channels of the underwater image to estimate the background light. Read More

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Resolution enhancement in random illumination microscopy using photon correlations.

Penghuan Liu

Appl Opt 2022 Apr;61(10):2910-2914

Random illumination microscopy (RIM) could surpass the diffraction barrier in fluorescence microscopy by illuminating an object with unknown speckle patterns. It has been demonstrated that the resolution in RIM using second-order statistics is as good as that of conventional structured illumination microscopy (SIM) from the asymptotic point of view. Compared to classical SIM, RIM is more robust to optical aberrations and scattering introduced by thick samples. Read More

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Resolution-enhanced ptychography framework with an equivalent upsampling and precise position.

Appl Opt 2022 Apr;61(10):2903-2909

As a lensless imaging technique, ptychography provides a new way to resolve the conflict between the spatial resolution and the field of view. However, due to the pixel size limit of the sensor, a compromise has to be reached between the spatial resolution and the signal-to-noise ratio. Here, we propose a resolution-enhanced ptychography framework with equivalent upsampling and subpixel accuracy in position to further improve the resolution of ptychography. Read More

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