Electromagnetic Multi–Gaussian Speckle

Generalizing our prior work on scalar multi-Gaussian (MG) distributed optical fields, we introduce the two-dimensional instantaneous electric-field vector whose components are jointly MG distributed. We then derive the single-point Stokes parameter probability density functions (PDFs) of MG-distributed light having an arbitrary degree and state of polarization. We show, in particular, that the intensity contrast of such a field can be tuned to values smaller or larger than unity. We validate our analysis by generating an example partially polarized MG field with a specified single-point polarization matrix using two different Monte Carlo simulation methods. We then compute the joint PDFs of the instantaneous field components and the Stokes parameter PDFs from the simulated MG fields, while comparing the results of both Monte Carlo methods to the corresponding theory. Lastly, we discuss the strengths, weaknesses, and applicability of both simulation methods in generating MG fields.

COMPARATIVE ANALYSIS OF THE PROPERTIES OF SODIUM NIOBATE AND SODIUM - LITHIUM NIOBATE CERAMICS

Авторами исследовано влияние температуры синтеза ниобата натрия, на состояние поляризации в образцах керамики чистого ниобата натрия и модифицированного литием. Проведено сравнительное исследование структуры и пироэлектрических свойств полученных образцов. Показано, что введение в качестве модификатора лития приводит к существенному изменению структуры в глубине образцов керамики на основе ниобата натрия. Если в глубине образцов чистого ни ниобата натрия, как и на поверхности, различаются отдельные зерна, то центральная часть керамики ниобата натрия-лития представляет собой сплошной массив, в котором отдельные зерна не наблюдаются. Во всех образцах, кроме чистого ниобата натрия, синтезированного двойным синтезом (первый при 650 °C, второй при 700 °C), установлено существование градиента поляризации по толщине образцов, направленного от стороны, соответствующей положительному концу вектора поляризации к стороне, соответствующей отрицательному концу вектора поляризации. The authors studied the effect of the temperature of sodium niobate synthesis on the state of polarization in ceramic samples of pure sodium niobate and modified with lithium. A comparative study of the structure and pyroelectric properties of the obtained samples has been carried out. It is shown that the introduction of lithium as a modifier leads to a significant change in the structure in the depth of ceramic samples based on sodium niobate. If in the depth of the pure sodium niobate samples, as well as on the surface, there are individual grains, then the central part of the sodium niobate-lithium niobate ceramics is a continuous mass in which individual grains are not observed. In all samples, except for pure sodium niobate, which was synthesized by double synthesis (the first at 650 °C, the second at 700 °C), the existence of a polarization gradient along the thickness of the samples was established. The gradient is directed from the side corresponding to the positive end of the polarization vector to the side corresponding to the negative end of the polarization vector.

Detection and study of polarized pulsed photoluminescence of diamonds for mapping of natural diamond

The bulk mapping of natural diamond poses problems where it is required to characterize various defects and measure their optical properties in volume. The combination of photoluminescence spectroscopy methods and methods for detecting the state of polarization in the volume will expand the functionality for mapping natural and artificial diamonds. The implemented methods will be an effective tool for the structural description of diamond optical centers.

Melanin concentration and depolarization metrics measurement by polarization-sensitive optical coherence tomography

Imaging of melanin in the eye is important as the melanin is structurally associated with some ocular diseases, such as age-related macular degeneration. Although optical coherence tomography (OCT) cannot distinguish tissues containing the melanin from other tissues intrinsically, polarization-sensitive OCT (PS-OCT) can detect the melanin through spatial depolarization of the backscattered light from the melanin granules. Entropy is one of the depolarization metrics that can be used to detect malanin granules in PS-OCT and valuable quantitative information on ocular tissue abnormalities can be retrived by correlating entropy with the melanin concentration. In this study, we investigate a relationship between the melanin concentration and some depolarization metrics including the entropy, and show that the entropy is linearly proportional to the melanin concentration in double logarithmic scale when noise bias is corrected for the entropy. In addition, we also confirm that the entropy does not depend on the incident state of polarization using the experimental data, which is one of important attributes that depolarization metrics should have. The dependence on the incident state of polarization is also analyzed for other depolarization metrics.