Features of thermal radiation of one-dimensional photonic structures on an absorbing substrate

The dependences of the thermal radiation (TR) lines contrast and amplitude of the systems (photonic structure)/substrate on the optical characteristics of both the photonic structure and the substrate have been investigated theoretically and experimentally. As it has been ascertained, these dependences demonstrate non-monotonic behavior, and the characteristics of the system TR can both increase and decrease depending on the ratio of individual optical parameters of the system components. The results of theoretical research were confirmed by experimental studies of TR systems Ge/GaAs, Ge/GaAs/Al, GaAs/Au and GaAs/(opaque substrate). The results of the research can be used in the development of narrow-band emitters for the middle and far IR range, which can be applied in the optical infrared devices for a wide range of applications.

Coexistence of light-induced thermocapillary and orientational effects in thin nematic films with a free surface

The effect of nonlinear light action on a thin (∼10 µm) films of the nematic liquid crystal deposited onto the absorbing substrate is experimentally investigated. The dynamics of the orientational and thermocapillary effects is directly studied. The two types of orientational processes were found out. The first one appears for several hundreds of milliseconds when the light beam irradiation is turned on or off. The second one develops much slowly and does not relax during the light beam irradiation.

Determination of the parameters of coherent magneto-optical layers on a finite absorbing substrate from thermal radiation spectra

A possibility of determining the parameters of a coherent magneto-optical layer on a finite incoherent absorbing substrate by analyzing the spectra of its thermal radiation (TR) has been investigated. On the example of a plane-parallel InAs semiconductor plate silver-coated on the back surface, it has been shown that a complex analysis of TR spectra, both without and with the presence of magnetic field, makes it possible to determine the thickness, optical, magneto-optical and electric parameters of the layer. Algorithms for the calculation and analysis of TR spectra are adduced, which simplify determination of layer parameters and increase the accuracy of results. Comparing the position of the extremes of the experimental zero-field spectrum with the theoretical calculations, the thickness of the sample and the plasma oscillation frequency in the used semiconductor have been determined. The analysis of the relative contrast of interference oscillations in the TR spectrum in the magnetic field using previously defined parameters enabled to ascertain the spectral dependence of the Faraday rotation angle and to determine the concentration, effective mass and type of current carriers. It has been assumed, that such analysis of luminescence spectra also allows determining the parameters of magneto-optical layers and structures.

Brewster angles for a dissipative film structure

The conditions of converting the reflection coefficients of plane TM or TE for a film-substrate dissipative structure are determined. As a result, the possibilities to maximize the measurement sensitivity by the THz spectroscopy method of the protein concentration in an aqueous solution are established, and the analytical solution to the inverse optical problem of determining the complex permittivity and thickness of a weakly absorbing film located on a weakly absorbing substrate is obtained.