The suggested composite channel model offers reference data for the development of a more reliable and inclusive underwater optical wireless communication link.

Coherent optical imaging utilizes speckle patterns to furnish important characteristic information about the scattering object. Speckle patterns are typically captured using Rayleigh statistical models, in conjunction with angularly resolved or oblique illumination geometries. A two-channel, polarization-sensitive, portable imaging device is employed to directly visualize terahertz speckle fields within a collocated telecentric backscattering configuration. The polarization state of the THz light, measured using two orthogonal photoconductive antennas, can be expressed as the Stokes vectors associated with the interaction of the THz beam with the sample. The method's validation, applied to surface scattering from gold-coated sandpapers, reveals a strong link between the polarization state, surface roughness, and the frequency of broadband THz illumination. We additionally illustrate non-Rayleigh first-order and second-order statistical characteristics, such as degree of polarization uniformity (DOPU) and phase difference, to ascertain the randomness of the polarization. This technique provides an expedient broadband THz polarimetric method for field-based measurements, with the potential for detecting light depolarization in various applications ranging from biomedical imaging to non-destructive testing scenarios.

For the security of many cryptographic operations, randomness, often in the form of random numbers, is an indispensable prerequisite. Adversaries, despite their complete awareness and control of the randomness source and the protocol, cannot prevent the extraction of quantum randomness. However, an aggressor can exploit the randomness by meticulously designing attacks to blind detectors, specifically targeting protocols that employ trusted detectors. Employing non-click events as valid data points, we present a quantum random number generation protocol capable of addressing both source vulnerabilities and sophisticatedly designed detector blinding attacks. The method's versatility allows for its application in high-dimensional random number generation. read more Experimental demonstration showcases our protocol's capability to generate random numbers for two-dimensional measurements, processing at a speed of 0.1 bit per pulse.

The acceleration of information processing in machine learning applications is a key driver of the growing interest in photonic computing. Computational applications utilizing reinforcement learning can benefit from the mode-competition mechanics of multimode semiconductor lasers, specifically in tackling the multi-armed bandit problem. Employing numerical methods, this study examines the chaotic mode competition dynamics of a multimode semiconductor laser, influenced by both optical feedback and injection. Longitudinal mode competition is observed and controlled by introducing an external optical signal into one of the modes. The dominant mode, defined by its superior intensity, is the one we identify; the proportion of the injected mode in the mix rises proportionally with the increased power of optical injection. The optical injection strength's influence on the dominant mode ratio's characteristics is mode-dependent, a consequence of varying optical feedback phases. We propose a control method which precisely adjusts the initial optical frequency mismatch between the optical injection signal and injected mode, thus impacting the dominant mode ratio characteristics. We further analyze how the area characterized by the largest dominant mode ratios correlates with the injection locking range. Dominant mode ratios, while prominent in a certain region, do not align with the injection-locking range. Multimode lasers' control technique, using chaotic mode-competition dynamics, presents promising applications for both reinforcement learning and reservoir computing in the field of photonic artificial intelligence.

Grazing incident small angle X-ray scattering, a surface-sensitive reflection-geometry scattering technique, is commonly used to provide an averaged statistical structural characterization of surface samples when studying nanostructures on substrates. If a highly coherent beam is utilized, grazing incidence geometry allows for the investigation of a sample's absolute three-dimensional structural morphology. Coherent surface scattering imaging (CSSI) employs a non-invasive methodology, mirroring coherent X-ray diffractive imaging (CDI), but utilizing small angles and grazing-incidence reflection geometry. A significant hurdle in CSSI processing stems from the incompatibility between conventional CDI reconstruction techniques and Fourier-transform-based forward models, which are unable to accurately model the dynamical scattering near the critical angle of total external reflection in substrate-supported samples. Our developed multi-slice forward model successfully simulates the dynamical or multi-beam scattering stemming from surface structures and the underlying substrate. Utilizing CUDA-assisted PyTorch optimization with automatic differentiation, the forward model effectively reconstructs an elongated 3D pattern from a solitary scattering image within the CSSI geometry.

For minimally invasive microscopy, an ultra-thin multimode fiber is an ideal choice due to its advantages of high mode density, high spatial resolution, and compact size. Practical applications demand a long and flexible probe, but this unfortunately compromises the imaging abilities of the multimode fiber. We introduce and experimentally demonstrate sub-diffraction imaging utilizing a flexible probe designed with a unique multicore-multimode fiber. The multicore part is comprised of 120 single-mode optical cores configured in a Fermat's spiral design. optical biopsy Optimal structured light illumination for sub-diffraction imaging is provided by the stable light delivery from each core to the multimode component. Fast sub-diffraction fiber imaging, which is impervious to perturbations, is accomplished by computational compressive sensing.

Manufacturing at the highest levels has always required the stable transmission of multi-filament arrays in transparent bulk materials, where the distance between individual filaments can be controlled and modified. The generation of a volume plasma grating (VPG), induced by ionization, is described here, stemming from the interaction of two collections of non-collinearly propagating multiple filament arrays (AMF). Employing spatial reconstruction of electrical fields, the VPG can externally direct the propagation of pulses along precisely structured plasma waveguides, which is differentiated from the spontaneous and random self-organization of multiple filaments stemming from noise. Pulmonary Cell Biology Readily adaptable crossing angles of excitation beams enable precise control over the filament separation distances observed in VPG. Through laser modification, utilizing VPG, a groundbreaking method for efficiently creating multi-dimensional grating structures within transparent bulk media was showcased.

The design of a tunable, narrowband thermal metasurface is reported, characterized by a hybrid resonance, produced from the interaction of a graphene ribbon with tunable permittivity and a silicon photonic crystal. A proximitized gated graphene ribbon array, coupled to a high-quality-factor silicon photonic crystal resonating in a guided mode, demonstrates tunable narrowband absorbance lineshapes with a quality factor exceeding 10000. Fermi level modulation in graphene, achieved through the application of gate voltage and fluctuating between high and low absorptivity states, produces absorbance on/off ratios exceeding 60. Coupled-mode theory provides a computationally efficient approach to metasurface design elements, leading to an exceptional speed boost compared to finite element analysis.

Numerical simulations and the angular spectrum propagation method are applied in this paper to a single random phase encoding (SRPE) lensless imaging system, allowing for a quantification of spatial resolution and a determination of its dependence on the system's physical parameters. Our miniature SRPE imaging system incorporates a laser diode to illuminate a sample positioned on a microscope slide, a diffuser to modify the light field traversing the input object, and an image sensor to record the intensity of the resultant modulated field. We have undertaken a detailed study of the optical field, propagated from two-point source apertures, as registered by the image sensor. Analysis of captured output intensity patterns at each lateral separation between input point sources involved correlating the overlapping point-sources' output pattern with the intensity of the separated point sources' output. The lateral resolution of the system was computed from the lateral separation of those point sources for which the correlation dropped below the 35% threshold, a value mirroring the Abbe diffraction limit of a corresponding lens-based system. Comparing the SRPE lensless imaging system to a similar lens-based imaging system with analogous system parameters, the results show that the SRPE system maintains equivalent lateral resolution performance despite its lensless design. The impact on this resolution of alterations in the parameters of the lensless imaging system has also been investigated. The robustness of the SRPE lensless imaging system to object-to-diffuser-to-sensor distances, image sensor pixel sizes, and image sensor pixel counts is evident in the obtained results. To the best of our information, this study presents the first work that explores the lateral resolution of a lensless imaging system, its tolerance to various system-related physical parameters, and a comparative analysis to lens-based imaging systems.

The efficacy of satellite ocean color remote sensing fundamentally depends on the atmospheric correction procedure. However, the majority of atmospheric correction algorithms in use presently overlook the consequences of Earth's curvature.