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7 µm and the measurement time is less than 1 h. The number of sampling points can reach about 50 million. To the best of our knowledge, our proposed system is the first to achieve full-surface defects detection of ICF capsules with such high efficiency and high resolution at the same time.In a digital hologram, the maximum viewing angle of a computer-generated hologram (CGH) is limited by pixel pitch due to the diffraction grating equation. Since reducing pixel size of display panel is challenging and costly, we propose a method to expand the viewing angle of a digital hologram by attaching an aligned pixelated random phase mask (PRPM) onto the CGH pattern based on analysis of simulation results. By introducing a phase-averaging process to the widely used iterative Fourier transform algorithm, an optimized CGH pattern can be obtained in conjunction with a PRPM. Based on scalar diffraction theory, viewing angle enhancement characteristics were verified by comparing the perspective views of a two-plane hologram using a virtual eye model. In addition, we performed full electromagnetic simulations that included effects due to potential fabrication errors such as misalignment, thickness variation, and internal reflections and diffractions between the CGH and random mask patterns. From the simulation results, by attaching a 1.85 µm-sized pixel pitch PRPM to a 3.7 µm CGH, the viewing angle can be easily expanded almost identical to that of a CGH with 1.85 µm-pixel pitch.Spatial light modulators (SLMs), which generate varying phase modulation, are widely used in coherent diffraction imaging. Random patterns are uploaded on the SLM to modulate the measured wavefront. However, a random pattern is highly complex and requires a reliable SLM. In addition, the uncorrelated terms generated from the random modulations need to be sufficiently captured using an imaging sensor with a high signal-to-noise ratio (SNR) to avoid stagnation during iterations. We propose an alternative structured phase modulation (ASPM) method. The modulations are composed of orthogonally placed phase bars that introduce uncorrelated modulations. The ASPM modulation can act as the phase grating; in addition, the modulated intensities are concentrated, which can be captured with a high SNR. The complexity of the ASPM patterns is significantly reduced, which is helpful for utilizing the SLM to generate reliable phase modulation.We devise an inline digital holographic imaging system equipped with a lightweight deep learning network, termed CompNet, and develop the transfer learning for classification and analysis. It has a compression block consisting of a concatenated rectified linear unit (CReLU) activation to reduce the channels, and a class-balanced cross-entropy loss for training. The method is particularly suitable for small and imbalanced datasets, and we apply it to the detection and classification of microplastics. Our results show good improvements both in feature extraction, and generalization and classification accuracy, effectively overcoming the problem of overfitting. This method could be attractive for future in situ microplastic particle detection and classification applications.In recent years, research efforts in the field of digital holography have expanded significantly, due to the ability to obtain high-resolution intensity and phase images. The information contained in these images have become of great interest to the machine learning community, with applications spanning a wide portfolio of research areas, including bioengineering. In this work, we seek to demonstrate a high-fidelity simulation of holographic recording. By accurately and numerically simulating the propagation of a coherent light source through a series of optical elements and the object itself, we accurately predict the optical interference of the object and reference wave at the recording plane, including diffraction effects, aberrations, and speckle. We show that the optical transformation that predicts the complex field at the recording plane can be generalized for arbitrary holographic recording configurations using a matrix method. In addition, we provide a detailed description of digital phase reconstruction and aberration compensation for a variety of off-axis holographic configurations. Reconstruction errors are presented for the various holographic recording geometries and complex field objects. While the primary objective of this work is not to evaluate phase reconstruction approaches, the reconstruction of simulated holograms provides validation of the generalized simulation method. The long-term goal of this work is that the generalized holographic simulation motivates the use of phase reconstruction of the simulated holograms to populate databases for training machine-learning algorithms aimed at classifying relevant objects recorded through a variety of holographic setups.In this paper, we present a confocal laser scanning holographic microscope for the investigation of buried structures. The multimodal system combines high diffraction limited resolution and high signal-to-noise-ratio with the ability of phase acquisition. The amplitude and phase imaging capabilities of the system are shown on a test target. For the investigation of buried integrated semiconductor structures, we expand our system with an optical beam induced current modality that provides additional structure-sensitive contrast. We demonstrate the performance of the multimodal system by imaging the buried structures of a microcontroller through the silicon backside of its housing in reflection geometry.We present spatially resolved measurements of the below-band-gap carrier-induced absorption and concurrent phase change in a semiconductor with the help of transmission digital holography. The application is demonstrated for a bulk GaAs sample, while the holograms are recorded with a conventional CMOS sensor. We show that the phase information enables spatially resolved monitoring of excess carrier distributions. Based on that, we discuss a phase-based approach for separation of carrier and heat related effects in the semiconductor optical response.Fiber imaging bundles are widely used as thin, passive image conduits for miniaturized and endoscopic microscopy, particularly for confocal fluorescence imaging. Selleck Crenolanib Holographic microscopy through fiber bundles is more challenging; phase conjugation approaches are complex and require extensive calibration. This paper describes how simple inline holographic microscopy can be performed through an imaging bundle using a partially coherent illumination source from a multimode fiber. The sample is imaged in transmission, with the intensity hologram sampled by the bundle and transmitted to a remote camera. The hologram can then be numerically refocused for volumetric imaging, achieving a resolution of approximately 6 µm over a depth range of 1 mm. The scheme does not require any complex prior calibration and hence is insensitive to bending.Based on the acousto-optic effect, we propose a new method to directly measure water sound velocity that avoids the error-like phase ambiguity brought by the piezoelectric effect that is broadly adopted in current methods. In the experimental setup we designed, the laser signal modulated by the propagating acoustic wave changes its phase suddenly when the wave crosses the two or more intercepting laser lines simultaneously. This new design creatively realizes the possibility to capture time information at the phase level in sound velocity measurement, which is hardly realized in the piezoelectric-effect-based methods. Utilizing the above principle and the derived mathematical calculation, the accuracy of sound velocity with good traceability can be obtained. The experimental results show that the repeatability of the measurement results is less than 0.0159 m/s, and the accuracy compared with the commercial sound velocity profiler is better than 0.02 m/s.A method for deriving the optical constants (n/k) of organic powdered materials using pressed pellets in the mid-infrared spectral range is introduced that combines variable angle spectroscopic ellipsometry and transmission spectroscopy. The approach is applied to anhydrous lactose, in which three different forms of pellets were pressed and measured a pure lactose pellet and a mixed lactose/potassium bromide (KBr) pellet with a large analyte percentage were used for ellipsometric measurements, and a KBr transmission pellet with only a small analyte percentage was used for transmission measurements. The transmittance data provide an initial set of oscillators and improve the spectral fitting of weak absorption features (k less then 0.01). Ellipsometric data for the pure and mixed pellets are then fit simultaneously to derive the final n/k values for lactose from 6000-400cm-1. An alternative method just using the ellipsometric data from the mixed pellet and the transmittance data is also presented and shows good agreement with the multi-sample analysis, providing a simpler method for powders that do not press easily into pure pellets. Finally, the derived optical constants were used to model the reflectance data, demonstrating a good match with the measured reflectance spectra if non-idealities are included.A switchable metasurface with dual functions of polarization conversion and filtering is proposed in this paper. The designed structure is composed of a medium-metal-medium-metal-medium structure, and VO2 is embedded in the metal metasurface. When VO2 is an insulated state, this structure can perform linear polarization conversion under terahertz wave normal incidence, and it has good asymmetric transmission capabilities. At the range from 2.01 to 2.86 THz, the polarization conversion rate is higher than 93%. When VO2 is in the metallic state, the structure becomes a broadband band-stop filter with a 3 dB bandwidth of 1.73 THz. The polarization conversion and filtering functions of the proposed structure can be converted to each other by changing the external temperature. This switchable multifunction structure provides a new way for the design of terahertz devices.In this paper, a Si3N4-CaF2 hybrid plasmonic waveguide (HPW) with an asymmetric metal cladding is designed for the mid-infrared polarization rotator (PR). The mode characteristics and polarization rotation performances of the Si3N4-CaF2 HPW-based PR are simulated by using the finite element method. Operating at the wavelength of 3.5 µm, the polarization conversion efficiency between two polarization modes (PM 1 and PM 2) is larger than 99% at a Si3N4-CaF2 HPW length of 104 µm. The Si3N4-CaF2 HPW-based PR maintains good polarization rotation performances within fabrication tolerances from -10 to 10 nm. The polarization rotator based on the Si3N4-CaF2 HPW paves the way to achieve integrated waveplates, driving many important optical functions from free space onto a chip.A periodic planar metamaterial sensor in the terahertz band based on surface plasmon polariton resonances is proposed and studied. The unit cell includes four half-elliptical graphene rings located on a three-layer substrate including a SiO2 layer, an air gap, and another SiO2 layer. The embedded air gap between the two layers of SiO2 improves the sensitivity of the sensor. Parametric study is performed, and the effects of the dimensions of the elliptical rings, the air gap thickness, and the Fermi energy of graphene on resonant frequency, sensitivity, and figure of merit (FoM) are investigated and graphically illustrated. The parameters of the sensor are optimized to provide a high sensitivity with a suitable FoM. By changing the refractive index of the sensing environment from 1.2 to 2, maximum sensitivity of 21.1 µm/RIU with FoM 5.14 is provided. The performance of the sensor is compared with previous works, and it is shown that a considerable improvement in sensitivity is achieved. The proposed sensor is suitable for biosensing applications.
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