D. A. Usanov

Determination of the metal nanometer layer thickness and semiconductor conductivity in metal-semiconductor structures from electromagnetic reflection and transmission spectra

Interaction of electromagnetic radiation with metal-semiconductor nanometer structures is studied theoretically and experimentally. A technique for nondestructive multiparametric control of the electrophysical parameters of metal nanometer layers and semiconductor conductivity in metal-semiconductor structures using electromagnetic reflection and transmission spectra is proposed and tested experimentally.

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.

Measurements of thickness of metal films in sandwich structures by the microwave reflection spectrum

The method for measurements of the thickness of nanometer metal films in sandwich structures by the microwave reflection spectrum had been proposed and implemented experimentally

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.

Dielectric matrices with air cavities as a waveguide photonic crystal

Frequency dependences of the transmission coefficient of a microwave photonic crystal that represents a structure containing alternating layers of ceramic material (Al2O3) with a relatively large number of cavities and foam plastic are studied in the presence and absence of distortions of the periodicity of a photonic structure. The frequency dependences of the transmission coefficient can be analyzed using a model of effective medium that makes it possible to consider the interaction of electromagnetic wave and photonic crystal using a transfer matrix of a 1D photonic crystal. The band character of the frequency dependence of the transmission coefficient of the photonic crystal related to the periodicity of the photonic crystal in the transverse plane for the waveguide with a standard cross section is not manifested in a certain range of material permittivities.

Autodyne interferometry for range-finding under laser radiation wavelength modulation

The results of solution of the inverse problem of determining the distance to the reflector in the case of current modulation of the laser radiation wavelength are presented. It is shown that current modulation of the autodyne signal amplitude can reduce the inverse problem of finding the distance to the reflector to a state of affairs characteristic only of phase modulation. The technique that we propose provides a higher range-finding accuracy than does direct analysis of the autodyne signal.

Dynamics of nanoparticle agglomeration in a magnetic fluid in a varying magnetic field

It is found that the dependence of the magnetic nanoparticle agglomerate length in a magnetic fluid on the applied magnetic field has three characteristic segments: a substantial increase in the agglomerate length with the magnetic field in the range of weak fields, a segment with an insignificant increase in the average length of agglomerates upon an increase in the field, and a sharp increase in the agglomerate length with a further increase in the field. It is shown that the agglomerate length increases in the range of strong magnetic fields due to a decrease in the spacing between adjacent agglomerates down to their complete coalescence. The total number of agglomerates decreases thereby.

Reconstruction of the form of complex motion of an object from the autodyne detection signal of a semiconductor laser

The possibility of reconstructing the shape of an interference signal on the basis of the autodyne detection signal of a semiconductor laser is demonstrated in cases of harmonic and nonharmonic vibrations of the object of study. The shape of the interference signal coincides with the shape of the signal of an interference system decoupled from the radiation source. It is shown that the form of nonharmonic vibrations can be reconstructed from the values of the autodyne signal function at four varying distances from the external vibrating reflector. Numerical simulation of the procedure of reconstruction of the shape of the interference signal was performed. The main limitations of the method under consideration are discussed.

Centimeter- and millimeter-wavelength matched loads based on microwave photonic crystals

Novel, small-sized broadband matched loads in the form of disordered photonic crystals containing nanometer metallic and insulating layers have been developed. It has been proposed to form insulating layers with different permittivities and low dissipation factors in both centimeter and millimeter wavelength ranges from the composites that consist of insulating matrices filled with air inclusions.

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.