Том 82, № 12 (2018)

The results are presented from investigating the light bullet spectrum in the filamentation of femtosecond pulses in calcium fluoride. A physical scenario is proposed for the generation of the anti-Stokes wing of the supercontinuum during the formation of the light bullet in the process of femtosecond filamentation in the mid-IR range.

We have studied the ultrafast response of a Bi₂Se₃ crystal to femtosecond laser pulses. We have observed an increase in the rise time of the electronic signal and the simultaneous increase in the amplitude of coherent phonons that occur when the central wavelength of the pump laser pulse is tuned from 1500 to 600 nm. These effects are interpreted as a result of screening of the electron–electron interaction by optical phonons.

The advantages of thin textured films over other resonant media that allow detection of the effect produced by the non-Faraday polarization twisting of photon echoes at room temperature are demonstrated. The possibility is discussed of using this effect to record record-short femtosecond time intervals, and for optical processors operating with quaternion algebra in order to effectively solve navigation problems in both aviation and medicine.

Principles of signal formation in analytical devices are considered. The similarity between requirements for signal processing systems is shown. Approaches are proposed that ensure the processing of overlapping peaks of a signal due to the use of original means of resolving and estimating the parameters of closely spaced peaks. The effectiveness of the proposed techniques and those used in analytical equipment is compared.

The physical principles of the operation of time-of-flight (ToF) cameras used for forming three-dimensional images are considered. Estimates of ToF camera characteristics are obtained using the example of a Kinect device. Algorithms for processing of three-dimensional images in a system of intraoperative navigation are described. Estimates of the accuracy of identifying the position of a surgical instrument are obtained.

Reasons for limitations in the transmittance of communication lines are considered. Ways of increasing the rate of data transfer and their shortcomings are described. It is proposed that coding sequences based on elementary circuits be used to make channels of communication denser.

A comparative analysis is performed of modern means of complexing images in laparoscopic surgery. A way of increasing the accuracy of complexing multispectral images using three-dimensional means, and of solving the problem of anatomical deformation via the application of augmented reality based on biophotonics, is proposed. The coincidence between additional information and a laparoscopic image is one advantage of approaches to augmented reality that are based on biophotonics, since the data originate from the same endoscope. Calibration of the camera is in this case not required, since the lens is naturally distorted in both augmented reality and the image.

The Liouville equation describing the time development of the density matrix of a single-photon packet propagating in an optical fiber is investigated. The Hamiltonian of the dynamic system and the relaxation operator depend on the phenomenological parameters: chromatic dispersion, polarization mode dispersion, polarization mode loss, and differential group delay. The patterns of distortion of a quantum packet are compared to the laws known from classical representations.

The planar form and two types of distorted molecular conformations in the ground electronic state for a number of metalloporphyrins in solid matrices exist simultaneously. A comparison of experimental data and results from quantum chemical calculations is discussed in order to analyze the structure of distorted porphyrin macrocycles at cryogenic temperatures.

The pseudo-Stark shift in the optical frequency of the ⁴F_9/2–⁴I_15/2 transition of an Er³⁺ ion in a Y₂SiO₅ matrix under the action of a weak pulsed electric field is measured from changes in the amplitude and temporal shape of the photon echo.

A family of precision power supplies designed for highly inductive superconducting magnets used in particle physics experiments is described. The power supplies have a rated output current in the ranges 0‒500 and 0–1300 A and are adapted to nonlinear highly inductive load behavior while maintaining high stability and output current parameters. Aspects of the safe extraction and recuperation of the accumulated reactive energy are considered.

Dense short electron bunches produced by state-of-the-art photoinjector-based accelerators are used to create sources of powerful electromagnetic pulses of terahertz frequency range based on spontaneous coherent emission by these bunches. However, there is a problem of stabilizing the phase dimension of a bunch along the space of electron wave interaction. In this work, two means of such stabilization are considered that are based on using the intrinsic electromagnetic fields (quasi-static and radiation) of bunches.

An efficient mode of the multistage capture and deceleration of particles in a sectioned undulator system for use in free electron lasers. This scheme is based on using a series of RF undulators with profiled resonant parameters that are powered by the independent powerful pulsed RF oscillators. The proposed mode allows efficiency to be obtained at a level of several percent in short-wavelength free electron lasers based on using dense bunches of electrons with relatively high energy spreads, formed in state-of-the-art laser plasma accelerators.

A compact THz FEL with a microtron as an electron source is currently under development at KAERI. It is based on a hybrid planar undulator with magnetic coils and a waveguide optical resonator. The dielectric coating of the waveguide and its lenticular cross section are used to reduce radiation losses and improve the efficiency of the optical resonator. The FEL uses an innovative scheme for the injection of electrons and outcoupling.