ИСТИНА

Surface diagnostics and optical communication are also a practical implementation of terahertz devices. Surface plasmon polaritons (SPPs) are widely exploited in these applications. In contrast to the visible spectral range with a very short length of SPP propagation, the experimentally measured propagation lengths of THz SPPs appeared to be macroscopic. THz plasmons can be used for thin layer detection and for information transmission in integrated optical systems. We thoroughly studied THz SPP formation, transport and diffraction at edges. In the latter case, the emerging radiation was found to be highly directional, which can be employed for remote probing, for instance. Surface plasmon characteristics are very sensitive to surface conditions and enable sensing of even sub-micron scale films. Another technique, which is now under development at the user station, involves a terahertz ellipsometer. Terahertz spectroscopy is a subject of special interest in biomedicine, chemistry and material science. FEL radiation is monochromatic, but, in contrast to other lasers, it can be continuously tuned within a wide spectral range. This feature enables developing spectroscopy techniques that require neither dispersion elements nor inverse Fourier transform processing. The advantage of high throughput is automatically applied to the FEL- based spectrometer. Since most substances of practical interest strongly absorb THz radiation, the absorption spectroscopy is often inapplicable in this region. For this reason, we have developed and implemented an imaging attenuated total reflection (ATR) spectrometer. It was applied to examination of numerous biologically important molecules. It is well known that enantiometry is an essential feature of such molecules. In particular, polysaccharide enantiomers can be used as markers of cancer risk. A Michelson-interferometer-based polarimeter with a movable mirror and ATR module has been developed and applied to study of enantiomers. Terahertz spectroscopy and ellipsometry were also used in the experiments on diffuse liver disease diagnostics via erythrocyte examination. Among other current studies we could mention the acousto-optic experiments and the development of a near-field terahertz microscope.