Projective filtering of a single spatial radiation eigenmode

Lossless filtering of a single coherent (Schmidt) mode from spatially multimode radiation is a problem crucial for optics in general and for quantum optics in particular. It becomes especially important in the case of nonclassical light that is fragile to optical losses. An example is bright squeezed vacuum generated via high-gain parametric down conversion or four-wave mixing. Its highly multiphoton and multimode structure offers a huge increase in the information capacity provided that each mode can be addressed separately. However, the nonclassical signature of bright squeezed vacuum, photon-number correlations, are highly susceptible to losses. Here we demonstrate lossless filtering of a single spatial Schmidt mode by projecting the spatial spectrum of bright squeezed vacuum on the eigenmode of a single-mode fiber. Moreover, we show that the first Schmidt mode can be captured by simply maximizing the fiber-coupled intensity. Importantly, the projection operation does not affect the targeted mode and leaves it usable for further applications.Comment: 10 pages, 9 figure

Bright squeezed vacuum in a nonlinear interferometer: frequency/temporal Schmidt-mode description

Control over the spectral properties of the bright squeezed vacuum (BSV), a highly multimode non-classical macroscopic state of light that can be generated through high-gain parametric down conversion, is crucial for many applications. In particular, in several recent experiments BSV is generated in a strongly pumped SU(1,1) interferometer to achieve phase supersensitivity, perform broadband homodyne detection, or tailor the frequency spectrum of squeezed light. In this work, we present an analytical approach to the theoretical description of BSV in the frequency domain based on the Bloch-Messiah reduction and the Schmidt-mode formalism. As a special case we consider a strongly pumped SU(1,1) interferometer. We show that different moments of the radiation at its output depend on the phase, dispersion and the parametric gain in a nontrivial way, thereby providing additional insights on the capabilities of nonlinear interferometers. In particular, a dramatic change in the spectrum occurs as the parametric gain increases

Properties of bright squeezed vacuum at increasing brightness

A bright squeezed vacuum (BSV) is a nonclassical macroscopic state of light, which is generated through high-gain parametric down-conversion or four-wave mixing. Although the BSV is an important tool in quantum optics and has a lot of applications, its theoretical description is still not complete. In particular, the existing description in terms of Schmidt modes with gain-independent shapes fails to explain the spectral broadening observed in the experiment as the mean number of photons increases. Meanwhile, the semiclassical description accounting for the broadening does not allow us to decouple the intermodal photon-number correlations. In this work, we present a new generalized theoretical approach to describe the spatial properties of a multimode BSV. In the multimode case, one has to take into account the complicated interplay between all involved modes: each plane-wave mode interacts with all other modes, which complicates the problem significantly. The developed approach is based on exchanging the (k, t ) and (ω, z) representations and solving a system of integrodifferential equations. Our approach predicts correctly the dynamics of the Schmidt modes and the broadening of the angular distribution with the increase in the BSV mean photon number due to a stronger pumping. Moreover, the model correctly describes various properties of a widely used experimental configuration with two crystals and an air gap between them, namely, an SU(1,1) interferometer. In particular, it predicts the narrowing of the intensity distribution, the reduction and shift of the side lobes, and the decline in the interference visibility as the mean photon number increases due to stronger pumping. The presented experimental results confirm the validity of the new approach. The model can be easily extended to the case of the frequency spectrum, frequency Schmidt modes, and other experimental configurations

Kinetics of grain refinemet in metallic materials during large strain deformation

The development of ultrafine grained microstructures in austenitic stainless steel and pure titanium subjected to large strain deformation was comparatively studied. The change in the volume fractions of newly developed ultrafine grains was used to quantify the progress in grain refinement during plastic deformatio

Optical Monitoring in Elaboration of Metal Matrix Composites by Direct Metal Deposition

AbstractDevelopment of composites with multi-functional properties is a challenging problem that could be solved by laser cladding. The objective of the present work is to demonstrate the advantages of optical monitoring in optimizing deposition of carbide-reinforced metal matrix composites. Multi-wavelength pyrometer and infrared camera are applied to analyse high temperature heat – and mass transfer in the cladding zone. The influence of laser power, laser cladding speed and powder feeding rate on the brightness temperature are studied. The thermal images of the molten pool obtained by infrared camera for different TiC contents in the powder blend are analysed as well as the beads geometry, microstructure and microhardness

Analysis of approaches to sterility testing of COVID-19 prevention vaccines

Preventive vaccination against SARS-CoV-2 infection is currently receiving close attention in the Russian Federation. Improving public confidence in immunisation with new vaccines largely depends on a guarantee of the absence of side effects caused by contamination. A high risk of contamination is inherent to biological products, including coronavirus prevention vaccines, due to their properties and the nature of raw materials used. This risk adds to the need for using effective contaminant detection approaches.The aim of the study was to evaluate the possibility to improve sterility testing of preventive vaccines against SARS-CoV-2 infection.This article presents an analysis of the procedures proposed by pharmaceutical developers for sterility testing of ten Russian vaccines approved in the country for COVID-19 prevention. The authors considered specific characteristics of these vaccines, including their physical and chemical properties, the presence of antimicrobial components, and other critical factors affecting the correctness of the experimental setup. The results suggest that it is possible to improve sterility testing. According to the authors, the main directions for its improvement are the proposal to develop an alternative procedure based on compendial method 2 (OFS.1.2.4.0003.15, Ph. Rus. XIV), as well as the use of a universal culture medium. If used for refining the established procedures and developing new ones, the authors’ recommendations will improve the reliability and applicability of sterility testing during both manufacturing and pre-approval regulatory assessment of updated coronavirus vaccines for subsequent release to the market. The proposed approaches can be applied to testing other medicinal products for sterility

Risk of fragility fractures in obese patients

The purpose of the study is to assess the association between BMI and the risk of fragility fractures in patients of the Fracture Liaison Service.Цель исследования – оценка связи между ИМТ и риском низкоэнергетических переломов у пациентов, обратившихся на прием по профилактике повторных переломов

Grain boundary assembly in a 316 L steel produced by selective laser melting and annealing

The effect of recrystallization annealing on the grain boundary assembly of a 316 L-type austenitic stainless steel produced by selective laser melting was studie