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It is shown that when counterpropagating laser beams are incident on an array of parallel single-walled carbon nanotubes, strong interaction of waves is possible, accompanied by the amplification of one of the waves at the expense of another, more intense pump wave. The interaction is most efficient when the condition of phase matching of the incident waves and the slow plasmon polariton wave formed because of the laser-induced metallisation of nanotubes is satisfied. The dependence of the the signal wave gain on the geometric parameters of the array and the wave characteristics of the incident waves is studied numerically. A range of phase detuning values is found, in which the gain changes weakly near its maximum value.

The problem of recognising single sparsely located scatterers against the noise background in the image obtained by the method of optical coherence tomography (OCT) is considered. An identification method based on the use of specific scanning features upon OCT image registration and on the statistical analysis of image fragments is proposed. The efficiency of the method is demonstrated experimentally in the diagnosis of otitis media with effusion. The approach can be used in the development of automated algorithms for determining the presence of highly transparent effusion in the middle ear cavity of a human with acute otitis media with effusion, including postoperative one.

The paper describes the design of an optical coherence tomograph adapted for studying the state of the tympanic cavity of the human middle ear. We present the images obtained by the method of optical coherence tomography, which are characteristic of the norm and of the case of pathology – otitis media with effusion.

Attenuation coefficient estimation from optical coherent tomography (OCT) data is one of the emerging methods for additional information extraction from the OCT data. With the reasonable assumptions of uniform proportion of the light, scattered backwards, relative to the light, scattered in all directions and the assumption of complete light attenuation within the imaging depth range, the attenuation coefficient can be estimated in every pixel of the OCT data volume, i.e. with the depth resolution. In the present paper the numerically effective method for lifting the second assumption was proposed. With numerical simulations and experiments it was shown, that the proposed method allows attenuation coefficient estimation even if OCT signal was not completely attenuated within the imaging depth range. Since the proposed method lifts one of the requirements for depth-resolved attenuation coefficient estimation, it allows the extension of the depth-resolved attenuation estimation method to the new applications.

The Galactic B[e] supergiant MWC 137 is surrounded by a large-scale optical nebula. To shed light on the physical conditions and kinematics of the nebula, we analyze the optical forbidden emission lines [NII] 6548,6583 and [SII] 6716,6731 in long-slit spectra taken with ALFOSC at the Nordic Optical Telescope. The radial velocities display a complex behavior but, in general, the northern nebular features are predominantly approaching while the southern ones are mostly receding. The electron density shows strong variations across the nebula with values spreading from about zero to ~800 cm$^{-3}$. Higher densities are found closer to MWC~137 and in regions of intense emission, whereas in regions with high radial velocities the density decreases significantly. We also observe the entire nebula in the two [SII] lines with the scanning Fabry-Perot interferometer attached to the 6-m telescope of the Special Astrophysical Observatory. These data reveal a new bow-shaped feature at PA = 225-245 and a distance 80" from MWC 137. A new H$\alpha$ image has been taken with the Danish 1.54-m telescope on La Silla. No expansion or changes in the nebular morphology appear within 18.1 years. We derive a mass of 37 (+9/-5) solar masses and an age of $4.7\pm0.8$ Myr for MWC 137. Furthermore, we detect a period of 1.93 d in the time series photometry collected with the TESS satellite, which could suggest stellar pulsations. Other, low-frequency variability is seen as well. Whether these signals are caused by internal gravity waves in the early-type star or by variability in the wind and circumstellar matter currently cannot be distinguished., Comment: 18 pages, 12 figures, Table 1 is only available in electronic form, submitted to AJ

Half-disk lasers fabricated by cleaving initial full-disk lasers have an advantage of directional light outcoupling as well as increased output power and efficiency as compared to full-disk lasers of the same diameter. The continuous wave output power of a 200 µm diameter half-disk laser exceeds 70 mW. Quasi single-mode lasing with a high side-mode suppression ratio more than 20 dB is demonstrated for half-disk lasers of various diameters. A maximum 3 dB small signal modulation frequency of 4.9 GHz was measured for a 100 µm in diameter half-disk laser.

The article presents the design and first test results of the neutron spectrometer with count rate up to 7 × 106 events per second with remote detector based on artificial diamond, intended for use on burning plasma experiments. The spectrometer consists of the broadband low-noise amplifier and the data acquisition and processing unit. The design of the amplifier with characteristic impedance matching of the cable line by the dynamic resistance of the transistor base-emitter junction is considered. The data acquisition and processing unit is realized using a real-time event-processing algorithm based on harmonic data analysis. This algorithm includes effective techniques for detecting and excluding overlaps and suppression of fluctuations in the baseline level corresponding to zero signal.

Small laboratory animals (rats) are suitable objects for modelling acute mesenteric ischemia (AMI) and monitoring changes in the structural tissue and intramural blood flow using optical coherence tomography (OCT) and OCT angiography methods. Combined with evaluation of blood circulation the prevalence of a necrotic tissue is a key factor in assessing intestine viability during surgery and determining the resection margins. While the assessment of the blood vessels network is commonly performed visually by surgeons, the assessment of the necrosis within individual layers is quite challenging due to small thickness of each intestine layer in small objects. The study demonstrates that the construction of colour-coded maps of the tissue attenuation coefficient estimated from the OCT data, allows quick layer-by-layer evaluation of the intestine wall. Such maps in the AMI model make it possible to track changes separately in the serous-muscular, submucosa and mucosa layers of the intestine wall in vivo and to carry out a differential diagnosis between the inflammation and necrosis in these layers. Colour-coded mapping may be useful in other medical applications where layer-by-layer assessment of structural tissue changes is required in a small range of depths.

Epi-side down bonding on a silicon substrate of AlGaAs/GaAs microdisk lasers is presented. A heterostructure with coupled large optical cavities enables location of an InGaAs quantum dot active region at a distance of ∼1 µm from the heterostructure surface. The thermal resistance was reduced to 0.2 and 0.1 K mW−1 for disks of 30 and 50 µm in diameter, respectively. The maximum continuous-wave power limited by the thermal rollover is more than doubled after bonding.

The article presents the results of research in the field of diagnostics of a traction electric motor of the 1DT.003.11 type of the alternating current electric train of the EP3D series by simulating emergency modes of functioning of the fuzzy logic of a modular dynamical neural network. It is proposed to solve the problems of assessing the reliability of traction electric motors in railway transport with an increased service life using simulation modeling of the ANFIS modular neural network in the MATLAB package. The result of modeling the statistical diagnostic parameters of the traction motor is an assessment of the change in the linguistic coefficients of the residual life of the traction motor of the EP3D electric train and recommendations for the maintenance of traction electric motors, depending on their technical condition at the current time of operation.

We consider a protocol of broadband quantum memory on a controlled frequency comb of spectral lines of ring microwave resonators connected to a common strip waveguide. A prototype of this memory is manufactured, on which the room-temperature preservation of microwave pulses with an efficiency of about 3 % is demonstrated. The experimentally obtained efficiency can be enhanced to a level above 90 % using modern microwave technologies and conducting experiments at helium temperatures, which opens a new way for the development of integrated microwave quantum memory.