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We report a technique for studying the absorption of optical radiation in layers of a semiconductor heterostructure by the method of probe radiation coupling. The studies are carried out using specially made isotype samples based on AlGaAs/GaAs, simulating an n-type doped laser waveguide with a concentration of 1017 – 1018cm−3. The main features of the experimental setup and calculation methods are described. A high (up to 95%) efficiency of light coupling into the waveguide and an error in measuring the absorption coefficient at a level of 0.1 cm−1 are achieved. The possibilities of studying the polarisation and temperature dependences of radiation absorption by free carriers are experimentally demonstrated. It is shown that with an increase in temperature in the range 25 – 85°C, the absorption in the samples increases by 15%.

A laser source for bleaching passive Q-switches of erbium-ytterbium lasers is developed and studied. The developed and studied compact pulsed module (peak power exceeding 10 W in a pulse with a duration of 1 μs at a wavelength around 1550 nm) is made on the basis of a semiconductor lasers with an ultra-narrow waveguide integrated with a pulsed pump card. To optimise the output laser characteristics, a series resistance was used in the laser pump circuit. The powers of the free-space and fibre-coupled modules at a temperature of 25 °C are 15 and 12 W, respectively, at a pulse shape close to rectangular.

We investigated the effect of AlInAs energy barrier layers on the edge-emitting lasers of 1400–1600 nm spectral range. It was shown that the barrier layer at the waveguide-cladding heterojunction provides charge carrier accumulation in the waveguide and prevents the internal quantum efficiency from drop. The use of barrier layer enables increasing the pulse optical power from 9 to 13 W from 100 μm aperture.

The majority of deaths related to complications of liver cirrhosis would have been preventable with timely diagnosis and proper treatment. However, absence of the population-based screening programs for hepatitis, an asymptomatic course of the majority of liver disorders, failures in the registration of etiologically confirmed cases of liver cirrhosis, low population awareness of its risks and of current diagnostic and management opportunities do impede the collection of reliable epidemiological data on the incidence and prevalence of liver disorders including their end-stages, and on the related mortality of the population; as a consequence, all these factors hinder a comprehensive assessment of the medical and social burden of hepatic disorders. Medical registries are the single system for their registration and follow-up. Analysis of data from the Moscow Regional Registry of patients with liver disease has shown that the leading cause of liver cirrhosis is HCV infection (66%), with alcoholic liver cirrhosis ranking second (16.1%). There is a trend towards higher proportions of liver cirrhosis as an outcome of HCV hepatitis among newly referred patients (7.2% in 2012 and 10.6% in 2016). HCV genotype characteristics determine the rates of the disease progression: in those with genotype 3, liver cirrhosis would occur at an earlier age (51.8% of patients aged from 26 to 45) than with genotype 1 (58.7% of patients aged from 46 to 65). In older patients, various comorbidities can contribute to the development of liver cirrhosis. Among patients with HBV infection, 4.9% have liver cirrhosis, and most of patients receive antiviral treatment with nucleoside/nucleotide analogues. The highest percentage of liver cirrhosis has been found in the patients with chronic D hepatitis (46/116, 39.7%). In 10.3% of the patients with chronic D hepatitis, the aggressive course of the disease leads to primary liver cancer. Thus, the necessity of the development of prevention measures and early detection of liver disorders, as well as modernization of the public healthcare system at all stages of medical care should be recognized as the short-term goals, in addition to the search for highly effective etiologic treatment and making it available within the state-financed programs.

High-order surface diffraction gratings acting as a distributed Bragg reflector (DBR) in mesa stripe semiconductor lasers (λ = 1030 nm) have been studied theoretically and experimentally. Higher order interfering radiation modes (IRMs), which propagate off the plane of the waveguide, have been shown to have a crucial effect on the reflection and transmission spectra of the DBR. The decrease in the reflectivity of the DBR in response to the increase in the diffraction efficiency of these modes may reach 80% and more. According to theoretical analysis results, the intensity of the higher order IRMs is determined by the geometry of the DBR groove profile. Experimental data demonstrate that the noncavity modes are responsible for parasitic light leakage losses in the laser cavity. It has been shown that, in the case of nonoptimal geometry of the grating groove profile, the overall external differential quantum efficiency of the parasitic laser emission may exceed 45%, which is more than half of the laser output power. The optimal geometry of the DBR groove profile is trapezoidal, with the smallest possible lower base. Experimental evidence has been presented that this geometry considerably reduces the power of the higher order IRMs and minimises the parasitic light leakage loss.

A method of studying the absorption coefficient in layers of semiconductor lasers is proposed. Using lasers based on MOVPE-grown separate-confinement heterostructures with a broadened waveguide, the absorption coefficient is investigated under pulsed current pumping. It is found that when the pump current flows through the laser in question, an additional internal optical absorption arises in the heterostructure layers. It is shown that an increase in the pump current density up to 20 kA cm-2 leads to an increase in absorption up to 2.5 cm-1. The feasibility of studying free-carrier absorption in the active region is demonstrated.

It was studied in systems constituted by aqueous solutions of 1,2,4-triazole, and NiO and Fe2O3 adsorbents how the electrokinetic potential of the surface of the oxides, amount of adsorbed triazole, and its concentration in solution vary during a long time.

This study aimed to examine anti hepatitis C virus (HCV) antibody titres, their changes and differences in acute, chronic and past HCV infection and to examine them after IFN-alpha-therapy. Ninety five patients were studied in a cross-sectional investigation and 18 of them were followed long-term. Titres of IgM and IgG antibodies against core, NS3, NS4 (A + B), NS5A proteins were determined by the third generation enzyme immunoassays. Patients with acute hepatitis C developed IgG antibodies against core protein in titres 1/5-1/800 and against individual NS proteins at the same titres. During the first to second month of acute hepatitis C IgG antibody titres to HCV proteins were very low, but they had risen considerably by the fourth to sixth month. Anti-HCV IgM antibodies were found in half the acute hepatitis serum samples, titres were 1/5-1/40. Sixty individuals with chronic hepatitis C showed IgG antibodies against core in titres 1/800-1/40,000 and against individual NS proteins in titres 1/5-1/20,000. Eight patients with chronic hepatitis C had invariable anti-HCV IgG antibodies over 2-3 years. About 81.7% of chronically infected patients had anti-HCV IgM antibodies in titres 1/5-1/160. Patients with resolution of HCV infection showed only anti-core IgG antibodies (titres 1/5-1/200) or no virus-specific antibodies. Individuals with different response to IFN-alpha-therapy showed two distinct patterns of anti-HCV antibody titres. Acute and chronic HCV infection may be distinguished by anti-core titres.

To study effectiveness of recombinant interferon-alpha (Ifna) in patients with chronic hepatitis C with normal transaminases.26 patients with positive tests for abHCV and RNA HCV with a normal level of alaninaminotransferase (AlAT) entered the study. 16 patients of the test group received recombinant Ifna three times a week in a dose 3 mln IU. Mean duration of interferon therapy was 7.44 +/- 4.27 months. Control group consisted of 10 patients with natural course of the disease. Biochemical, virusological and morphological examinations were conducted in all the patients. The patients were followed up for 1.5-2 years, on the average.Treatment with recombinant Ifna was well tolerated. A persistent positive virusological response after the treatment was achieved in 25% of the test patients. They exhibited improvement of histological structure of the liver. In control group the dynamics was opposite.In patients with chronic hepatitis C with normal transaminases level interferon therapy improves structure of hepatic tissue. Puncture biopsy of the liver is the main method which determines the validity of the treatment and its efficacy.