A. V. Skripal

Complex permittivity of composites based on dielectric matrices with carbon nanotubes

The transmission spectra of microwave electromagnetic radiation interacting with a sample are used to determine the complex permittivity of a composite material based on a two-component epoxy adhesive having a certain volume fraction of inclusions in the form of multilayer carbon nanotubes or fine graphite particles. An inverse problem is solved for the dependence of the complex permittivity of the composite material on the volume fraction of carbon nanotubes, and their permittivity and average bulk electrical conductivity are determined.

Microstrip photonic crystals used for measuring parameters of liquids

Computer simulation and experimental study of the frequency dependences of the transmission and reflection coefficients of photonic crystals based on a microstrip structure are carried out in the case when the periodicity of the structure is violated by a change in the permittivity of the substrate of one of the alternating segments of the microstrip line. A method is developed for measuring parameters of the material playing the role of inhomogeneity in the open microwave photonic structure. The complex permittivity is determined for a number of polar and nonpolar liquids.

Waveguides containing frame elements with electrically controlled characteristics of permitted and forbidden bands

The feasibility of waveguide structures that have both forbidden and permitted transmission bands and are based on a diaphragm and frame coupling elements placed on both of its sides is shown experimentally and numerically using the finite element method. It is found out that the dynamic range of controlling the transmission coefficient by means of an n-i-p-i-n-structure placed in the gap between the post and the frame elements attains 23.5 dB, the transmission loss level not exceeding 1.5 dB.

Acoustic pressure induced period-doubling bifurcations in tympanic membrane oscillations

We demonstrate the possibility of using a quantum-confined semiconductor structure laser operating in the autodyne regime for the investigation of the amplitude-frequency characteristics of the tympanic membrane (TM). Using such a laser, it is established that an increase in the acoustic pressure leads to the appearance of subharmonics in the spectrum of TM oscillations at frequencies equal to one-half and one-quarter of the exciting signal frequency, which is evidence for period-doubling bufurcations.

Variation of the type of resonance reflection of electromagnetic radiation from metal nanolayer-dielectric layer structures

Two types of resonance reflection of electromagnetic radiation from metal nanolayer-dielectric layer structures have been theoretically predicted and observed in experiment. These structures can obey the conditions of a half-wave resonance at a small metal layer thickness, and a quarter-wave resonance at a greater metal layer thickness.

Optical control of semiconductor synchronized microwave oscillators in the signals subtraction scheme

The influence of optical radiation on the performance of the synchronized microwave oscillator in the scheme of the coherent signals (synchrosignal and oscillator output signal) subtraction on the common load has been described theoretically and investigated experimentally. The high sensitivity of the characteristics of investigated scheme on the base of synchronized Gunn-diode oscillator has been shown.

Optical control of semiconductor synchronized microwave oscillators in the power suppression mode

The influence of optical radiation on the performance of a synchronized microwave Gunn-diode oscillator in the coherent signals subtraction mode has been described theoretically and investigated experimentally. The high sensitivity of the oscillator characteristics to the change of the optical intensity affecting the semiconductor diode structure has been shown. It is suggested to use this mode for the creation of optoelectronic microwave systems with the controlled amplitude and phase of the output signal and for the high-accuracy indication of optical radiation.

Determination of mechanical vibration form of external reflector by response of autodyne interference system based on a semiconductor laser

The influence of parameters of external optical feedback on the character of autodyne signal of semiconductor laser has been investigated. For harmonic and non-harmonic mechanical vibrations the possibility of restoration of interference signal function for autodyne system has been shown.

Bragg microwave structures based on waveguide-slot lines

It is shown that a new type of the Bragg structure based on pieces of a waveguide-slot line can be created in the microwave band. The amplitude-frequency characteristics of such a structure are described theoretically and investigated experimentally in the frequency range 8–12 GHz. The regularities in the distribution of the electric field intensity in a standing wave appearing in the investigated Bragg structure are established. It is found that a resonance singularity appears in the forbidden zone of the investigated Bragg structure when a defect in the form of the changed length of the central section of a regular waveguide is made.

Control of the microwave characteristics of composite materials filled with carbon nanotubes using UV irradiation

The complex permittivities of composite materials that are based on the two-component epoxy binder with various volume concentrations of the UV-irradiated multilayer carbon nanotubes are determined using the microwave transmission spectra. The effect of the UV-irradiation time on the mean conductivity of the nanotubes in the composite in the microwave range is studied. It is demonstrated that the limitations on the working volume of the chamber in which the UV irradiation of the carbon nanotubes is performed substantially affects the electrophysical characteristics of the nanotubes.