As it is well known, terahertz time-domain spectroscopy is very perspective method for identification of molecules. The main difficulty of its application, on our opinion, is an absent of high effective method for temporal analysis of the medium response spectrum. According to [13] methods, using in time-domain spectroscopy for treatment of experimental results, have some bad features, which lead to absurd results sometimes. In [14,15,20,21] we developed two possible ways to create effective algorithms for the analysis of instantaneous spectral intensities of medium responce under the e action of pulse with a few cycles. It should be stressed that in the first algorithm we used the Gabor-Fourier window transform, investigated its efficiency and formulated requirements to its parameters for reconstruction of spectral dynamics of medium response with high quality. The second algorithm, based on application of SVD method, allows to obtain an information about many spectral lines simultaneously from one series of measurements of medium response characteristics. In both algorithms, their parameters were ideal ones without any random fluctuations. This paper deals with the more realistic situation: we investigate possibility to get dynamics of any spectral lines of medium response when parameters of measurements are random. Our investigation demonstrates the high efficiency of using method based on SVD algorithm. We apply it as for ideal medium response constructed on the base of some ideal oscillators, as for results of physical experiments. Also below the new approach to finding of instantaneous spectral amplitudes for requiring frequencies under the action of terahertz pulse is proposed. It allows to investigate a frequency dynamics due to using of integral measurements of optical signal.
INTRODUCTIONAs it is well known, now optics of laser pulses with a few cycles and pulses with terahertz frequency is developed very intensively. It is a consequence of wide practical application of terahertz radiation for time-domain spectroscopy, for example. It should be stressed that terahertz pulse with picoseconds duration is one with a few cycles as femtosecond pulse (10-20 fs) with frequency belonging to visible diapason. Terahertz radiation is very perspective for remote sondage and for the spectroscopy of chemical, biological objects and semiconductor [1-6]. With its help, it is possible to carry out diagnostics harmless to the person [7-9] and as well to control of chemical reactions and electron states in quantum wells, to create systems of safety and wireless connection between computers and peripheries in room [10][11][12].Obviously, under the action of pulses with a few cycles the medium response becomes essentially non-stationary. In this connection, it is of great interest an analysis of dynamics of its spectral lines for practice. Hence, creation of methods, which allow to analyze the spectral dynamics of medium response, is an actual problem. It is necessary to emphasize that Wigner's method, which is wide use in ...
