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This verifies the accuracy of the model and the effectiveness of the optimization method.Vacuum chambers are frequently used in high-energy, high-peak-power laser systems to prevent deleterious nonlinear effects, which can result from propagation in air. In the vacuum sections of the Allegra laser system at ELI-Beamlines, we observed degradation of several optical elements due to laser-induced contamination (LIC). This contamination is present on surfaces with laser intensity above 30GW/cm2 with wavelengths of 515, 800, and 1030 nm. It can lead to undesired absorption on diffraction gratings, mirrors, and crystals and ultimately to degradation of the laser beam profile. Because the Allegra laser is intended to be a high-uptime source for users, such progressive degradation is unacceptable for operation. Here, we evaluate three methods of removing LIC from optics in vacuum. One of them, the radio-frequency-generated plasma cleaning, appears to be a suitable solution from the perspective of operating a reliable, on-demand source for users.Light absorption by the water column plays an important role in the spatial and temporal distribution of light attenuation, mixed layer heating, primary productivity, and phytoplankton biomass in the water column. The absorption properties of water components are the main influences of the underwater light field and surface spectrum. The study of the absorption properties of the water body contributes to the understanding of its optical properties and the remote sensing inversion of water quality parameters. The effects of light source polarization on the spectral absorption coefficient measurements of colored dissolved organic matter (CDOM) and total particulate matter (TPM) in water were investigated by measuring the polarization of the light source in a UV-Vis spectrophotometer. The results show that the light source of the UV-Vis spectrophotometer is significantly polarized, but the effect of the polarization of the light source on the measurement of the spectral absorption coefficients of CDOM and TPM in water is very small and almost negligible.Flame chemiluminescence tomography (FCT) is a non-intrusive method that is based on using cameras to measure projections, and it plays a crucial role in combustion diagnostics and measurement. Mathematically, the inversion problem is ill-posed, and in the case of limited optical accessibility in practical applications, it is rank deficient. Therefore, the solution process should ideally be supported by prior information, which can be based on the known physics. In this work, the total variation (TV) regularization has been combined with the well-known algebraic reconstruction technique (ART) for practical FCT applications. The TV method endorses smoothness while also preserving typical flame features such as the flame front. Split Bregman iteration has been adopted for TV minimization. Five different noise conditions and the chosen regularization parameter have been tested in numerical studies. Additionally, for the 12 perspectives, an experimental FCT system is demonstrated, which is utilized to recover the three-dimensional (3D) chemiluminescence distribution of candle flames. Both the numerical and experimental studies show that the typical line artifacts that appear with the conventional ART algorithm when recovering the continuous chemiluminescence field of the flames are significantly reduced with the proposed algorithm.To circumvent elaborate conventional lithographic methods for realizing metallic nanostructures, it is necessary to develop self-organized nanofabrication methods for suitable template structures and their optical characterization. We demonstrate the potential of ion bombardment with impurity co-deposition to fabricate terraced or quasi-blazed nanostructure templates. Self-organized terraced nanostructures on fused silica were fabricated using Ar+ ion bombardment with iron impurity co-deposition and subsequent Au shadow deposition. The aspect ratios are enhanced threefold, and the range of nanostructure period variation is significantly increased with respect to that of conventional nanostructures realized by pure ion bombardment. We reveal the key features of the method via atomic force microscopy and optical characterization. Variable-profile quasiperiodic nanostructures with periods of 100-450 nm, heights of 25-180 nm, and blaze angles of 10°-25° were fabricated over an area of 20×40mm2, and these exhibited tunable and broadening optical anisotropy across the nanostructured area. Thus, the proposed method is a viable technique for rapid, cost-effective, and deterministic fabrication of variable nanostructure templates for potential optical applications.Laser-induced breakdown spectroscopy was used to determine the relationship between the spectral line intensity and surface hardness of 3D printed 18Ni300 maraging steel. Research found that there is a linear relationship between the spectral intensity ratio of ion line to atomic line and the surface hardness of the samples. This linear relationship is closely related to the selected elements and spectral lines. Selleck TBK1/IKKε-IN-5 The weak self-absorption spectrum of minor elements can obtain a better linear relationship. We study the effect of the number of laser pulses on the linear relationship. The results show that the ideal results can be obtained by using 100 pulses, which can minimize the damage to the sample.We propose a new nonlinear amplifying loop mirror (NALM)-based phase-preserving amplitude regenerator (so-called NP-NALM) by introducing a nonreciprocal phase shifter to further improve the regeneration performance. The theoretical model of the NP-NALM structure and the amplitude regeneration and phase-preserving conditions are presented. It is shown that the optimal working point power reduces with the increase of the nonreciprocal phase shift in the available range and the first working point power can be as low as 115 mW by optimizing the nonreciprocal phase shifter. We also investigate the cascaded NP-NALM transmission system for quadrature phase-shift keying signals with amplified spontaneous emission noise and the output error vector magnitude (EVM) can reduce to 23% from the EVM limit of 30%, corresponding to bit error ratio of 10-3 for the cascaded system without regeneration.Silicon-based optical phased arrays (OPAs) have been widely explored, while the design of the structure with high sidelobe level reduction, remains a big challenge. This work investigated the optimization of the optical path-modulated 3D OPAs with Si3N4 as the core layer and SiO2 as the cladding layer. We used the particle swarm optimization algorithm to optimize high-performance random distributed OPAs. Our study provides an effective pathway to optimize the random distributed OPAs within a controllable time frame among a vast number of parameters.Altering wavelength via fluorescent particles is used in various applications. The solution of the broadband radiative transfer equation (RTE) for absorbing and anisotropically scattering a fluorescent medium is presented in this study considering fluorescent cascade, along with a Monte-Carlo-method-based solution of the equation. The path-length-based Monte Carlo method, the dual-stage method, and its modified version, the multi-stage method, which are used for solving the RTE in a fluorescent medium for biomedical and lighting applications, are not capable of accurately solving the broadband RTE with fluorescent cascade. Therefore, a collision-based Monte Carlo method is applied to overcome the limitations of these approaches. An accuracy comparison with the alternative methods is presented along with the flow chart and codes of the proposed method.A new autofocusing algorithm for digital holography is proposed based on the eigenvalues of the images reconstructed at different distances in the measurement volume. An image quality metric evaluated based on the distribution of its eigenvalues is compared in function of the reconstruction distance to identify the location of the focal plane. The proposed automatic focal plane detection algorithm is capable of working with amplitude objects, phase objects, and mixed type objects. A performance comparison of the proposed algorithm with some previously reported representative algorithms is provided. The simulation and experimental results demonstrate the practical applicability of the proposed algorithm.In this paper, we present a noniterative method for 3D computer-generated holography based on deep learning. A convolutional neural network is adapted for directly generating a hologram to reproduce a 3D intensity pattern in a given class. We experimentally demonstrated the proposed method with optical reproductions of multiple layers based on phase-only Fourier holography. Our method is noniterative, but it achieves a reproduction quality comparable with that of iterative methods for a given class.Field spectral sensors provide real-time, reliable, quantitative monitoring of crop growth. Fitting the continuous growth in the entire growing period from the measurements of limited frequency is helpful to the comparative analysis of interannual growth and fertilizer management in the field. To exploit this capacity, our work presents a model that uses the normalized difference red edge (NDRE) index derived from the field spectral sensor for real-time monitoring of the canopy growth of winter wheat in the whole growing period. We developed this model from experiments in three counties in Hebei province, China, where we obtained the near-infrared and red edge reflectance, grain yield, and canopy parameters for eight growth stages and for various nitrogen (N) rates. Given the correlation between effective accumulated temperature and crop growth, we used the growing degree-days as an adjustment parameter to develop models for dynamic monitoring of the NDRE of the winter wheat canopy during the entire growing period. The results show that high determination coefficients (R2=0.89 to 0.96) are obtained from all models based on relative NDRE and effective accumulative temperature (independent of N fertilization rates). The model based on the rational function is the best of all models tested, with the accuracy for normal and high N fertilization rates being slightly greater than that for low N fertilization rates. Therefore, a relative-NDRE model with the accumulative growing degree-days since sowing could allow monitoring canopy NDRE of winter wheat at any time, which could be helpful for overcoming the shortage of incomparable growth derived from the differences of sensing date, sowing date, and fertilizer, etc.In this study, we developed a line-field Fourier domain optical coherence tomography (LF-FDOCT) system that performs lateral scanning using a two-dimension spatial light modulator and detects multiple channels of spectral domain OCT signal in parallel using a two-dimensional sensor. The LF-FDOCT system eliminates the need for mechanical scanning to acquire volumetric OCT data. It allows parallel acquisition of signal for B mode scan imaging through snapshot detection and offers unprecedented flexibility to select a fast scanning dimension. In this work, we describe the principle of LF-FDOCT imaging and present experimental results to demonstrate the effectiveness of this technology.