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Recently, orbital angular momentum (OAM) rays passing through free space have attracted the attention of researchers in the field of free-space optical communication systems. Throughout free space, the OAM states are subject to atmospheric turbulence (AT) distortion leading to crosstalk and power discrepancies between states. In this paper, a novel chaotic interleaver is used with low-density parity-check coded OAM-shift keying through an AT channel. Moreover, a convolutional neural network (CNN) is used as an adaptive demodulator to enhance the performance of the wireless optical communication system. The detection process with the conjugate light field method in the presence of chaotic interleaving has a better performance compared to that without chaotic interleaving for different values of propagation distance. Also, the viability of the proposed system is verified by conveying a digital image in the presence of distinctive turbulence conditions with different error correction codes. The impacts of turbulence strength, transmission distance, signal-to-noise ratio (SNR), and CNN parameters and hyperparameters are investigated and taken into consideration. The proposed CNN is chosen with the optimal parameter and hyperparameter values that yield the highest accuracy, utmost mean average precision (MAP), and the largest value of area under curve (AUC) for the different optimizers. The simulation results affirm that the proposed system can achieve better peak SNR values and lower mean square error values in the presence of different AT conditions. By computing accuracy, MAP, and AUC of the proposed system, we realize that the stochastic gradient descent with momentum and the adaptive moment estimation optimizers have better performance compared to the root mean square propagation optimizer.On-the-fly remote laser processing plays an increasingly important role in modern fabrication techniques. These processes require guiding of the focus of a laser beam along the contours of the workpiece in three dimensions. State-of-the-art galvanometer scanners already provide highly dynamic and precise transverse x-y beam steering. However, longitudinal focus shifting ("z-shifting") relying on conventional optics is restricted to a bandwidth of a few hundred Hz. see more We have developed and manufactured a fast piezo-based z-shifting mirror with diffraction-limited surface fidelity providing a focus shift of Δz>60mm with an actuation rate of 2 kHz.In this work, a generic exhaust gas test bench is introduced on which reproducible experiments can be performed to gain a deeper understanding of processes during exhaust gas aftertreatment of internal combustion engines. We present the design and initial flow characterization as well as tomographic measurement results of gaseous water distributions. The aim of the development was to provide a generic geometry as well as highly reproducible process boundary conditions for numerical simulation of exhaust aftertreatment phenomena. The presented initial measurements are intended to demonstrate the qualification of the test bench for extensive experimental characterization ranging from measurements of the spray injection, film evaporation, and reaction kinetics to the highly complex multiphase flow conditions during selective catalytic reduction (SCR) processes, which are characterized by high mass flows and temperatures, pronounced transients, and a corrosive atmosphere.A novel two-step method for manufacturing microlens array molds by combining microindentation and precision polishing is proposed. Compared with conventional manufacturing methods, such as single-point diamond turning, this two-step method, as an alternative method, presents great advantages on cost and flexibility on spherical microlens array mold fabrication. Various curvatures of radii and arrangements for microlens array molds can be fabricated in the same way. In this paper, a hexagonal microlens array with 1.58 mm curvature radius was demonstrated to prove the feasibility of the proposed method. First, a large number of precise steel balls were organized in hexagonal arrangement and pressed into the mold's surface to generate multiple microdimples. Second, the pileups around the microdimples were removed from the mold surface by precision polishing. The geometrical accuracy and surface quality were investigated by an optical surface profiler. The measurement indicated that, compared with the initial surface, the surface inside the dimple had significantly higher hardness and better surface quality than that of the steel balls. Then the microlens array on the mold was further replicated to poly(methyl methacrylate) substrates by a precision compression molding process. The experimental results showed that the fabricated mold and the polymer replicas have high fidelity, great uniformity, and good surface roughness. The proposed two-step, low-cost mold fabrication method can produce highly uniform microlens arrays and is therefore suitable for high-volume fabrication of precise optical elements such as integrated light-emitting diodes and other similar micro-optics.The microlens array has been widely applied in LED lighting source due to its special optical properties, but most of the research lacks the analysis and optimization of the complete mathematical models. Hence, the new design method of a free-form surface microlens array optical system is proposed in this paper. Based on the characteristics of TIR and the law of refraction, a complete mathematical model of the free-form microlens is established. By numerically solving a set of differential equations, the profile of the free-form surface microlens is obtained. Then we rotate the profile to get the free-form surface microlens. Finally, the proposed microlens array is simulated and analyzed in near-field and far-field situations, respectively. We also discuss the influence of microlens array characteristics on illumination performance. The result shows the uniformity and efficiency have been improved, both of which can reach more than 90%.A simple reservoir computing (RC) system based on a solitary semiconductor laser under an electrical message injection is proposed, and the performances of the RC are numerically investigated. Considering the lack of memory capacity (MC) in such a system, some auxiliary methods are introduced to enhance the MC and optimize the performances for processing complex tasks. In the pre-existing method, the input information is the current input data combined with some past input data in a weighted sum in the input layer (named as M-input). Another auxiliary method (named as M-output) is proposed to introduce the output layer for optimizing the performances of the RC system. The simulated results demonstrate that the MC of the system can be improved after adopting the auxiliary methods, and the effectiveness under adopting the M-input integrated with the M-output (named as M-both) is the most significant. Furthermore, we analyze the system performances for processing the Santa Fe time series prediction task and the nonlinear channel equalization (NCE) task after adopting the above three auxiliary methods. Results show that the M-input is the most suitable for the prediction task while the M-both is the most appropriate for the NCE task.Papillary carcinoma is the most prevalent type of thyroid cancer. Its diagnosis requires accurate and subjective analyses from expert pathologists. Here we propose a method based on the Hough transform (HT) to detect and objectively quantify local structural differences in collagen thyroid nodule capsules. Second harmonic generation (SHG) microscopy images were acquired on non-stained histological sections of capsule fragments surrounding the healthy thyroid gland and benign and tumoral/malignant nodules. The HT was applied to each SHG image to extract numerical information on the organization of the collagen architecture in the tissues under analysis. Results show that control thyroid capsule samples present a non-organized structure composed of wavy collagen distribution with local orientations. On the opposite, in capsules surrounding malignant nodules, a remodeling of the collagen network takes place and local undulations disappear, resulting in an aligned pattern with a global preferential orientation. The HT procedure was able to quantitatively differentiate thyroid capsules from capsules surrounding papillary thyroid carcinoma (PTC) nodules. Moreover, the algorithm also reveals that the collagen arrangement of the capsules surrounding benign nodules significantly differs from both the thyroid control and PTC nodule capsules. Combining SHG imaging with the HT results thus in an automatic and objective tool to discriminate between the pathological modifications that affect the capsules of thyroid nodules across the progressions of PTC, with potential to be used in clinical settings to complement current state-of-the-art diagnostic methods.Practical formulas are derived for calculating the far-field radiation pattern and coupling coefficient of a rectangular dielectric resonator (cuboid) with free space as well as mutual coupling coefficients between two cuboids for their different orientations relative to each other. An approach is developed using the coupled mode theory and the perturbation theory for the Maxwell equations. The correctness of obtained formulas is checked against the full-wave numerical simulations performed by the COMSOL Multiphysics electromagnetic solver. In particular, the obtained formulas can be used for revealing optical features of realistic (i.e., consisting of a finite number of resonators) all-dielectric metasurfaces with arbitrary curved shapes.Current methods to retrieve optically relevant properties from ocean color observations do not explicitly make use of prior knowledge about property distributions. Here we implement a simplified Bayesian approach that takes into account prior probability distributions on two sets of five optically relevant parameters, and conduct a retrieval of these parameters using hyperspectral simulated water-leaving reflectances. We focus specifically on the ability of the model to distinguish between two optically similar phytoplankton taxa, diatoms and Noctiluca scintillans. The inversion retrieval gives most-likely concentrations and uncertainty estimates, and we find that the model is able to probabilistically predict the occurrence of Noctiluca scintillans blooms using these metrics. We discuss how this method can be expanded to include a priori covariances between different parameters, and show the effect of varying measurement uncertainty and spectral resolution on Noctiluca scintillans bloom predictions.In this paper, a novel and efficient approach for solving the beam propagation method (BPM) governing equation is proposed. The approach is based on the reformulation of the beam propagation equation to solve real system matrices only at each propagation step. The reformulated equation utilizes a leap-frog (LF) technique to couple the real and imaginary components of the field in an iterative scheme. The method yields higher processing speed by at least 30% more than that of the conventional BPM method. To validate the proposed LF-BPM method, different photonic systems, including directional couplers and multimode interferometers, are simulated. Results have been experimentally verified by comparing them with results measured for fabricated micro-photonic structures. A stability analysis was performed to study the effect of the design parameters on the performance of the proposed scheme. The proposed LF-BPM approach is considered a promising technique for efficient modeling of optical structures.