We have studied for the first time the simultaneous generation of terahertz and X-ray radiation from noble gas based nano-cluster supersonic jet under “one-” and “two-color” (fundamental and its second harmonic) excitation with high-power femtosecond laser pulses. It was shown that optimal conditions for effective generation of terahertz and X-ray radiation are different. That makes possible efficiently control the magnitudes of terahertz and X-ray signals simultaneously generated from gas nano-cluster jet. Controlling could be provided by different means: by varying of time delay between laser pulse and cluster jet formation moment, or by varying of chirp parameter of laser pulses. Also we shown that efficiency of THz generation from cluster jet could be effectively controlled by varying of ratio between clustered and buffer (carrier) gases in mixture. Angular distribution of terahertz beam generated near by optical axis under “two-color” laser excitation conditions has been measured as well.

This paper briefly examines methods for the generation of pulsed terahertz radiation and principles of pulsed terahertz spectroscopy, an advanced informative method for studies of complex biological and nanostructured systems. Some of its practical applications are described. Using a number of steroid hormones as examples, we demonstrate that terahertz spectroscopy in combination with molecular dynamics methods and computer simulation allows one to gain information about the structure of molecules in crystals. A 'terahertz colour vision' method is proposed for analysis of pulsed terahertz signals reflected from biological tissues and it is shown that this method can be effectively used to analyse the properties of biological tissues and for early skin cancer diagnosis.

The nonlinear optical crystal grown from the melt GaSe∶ AgGaSe2(10%,mass percent) is identified as acentrosymmetric e-GaSe∶ Ag(≤0.04%,mass percent) and is used for phase matched frequency conversion.The silver presence results in 30% increase in microhardness,which allows the crystal to be cut and polished at arbitrary direction.The optical properties from visible to mid-IR and further THz ranges are studied in detail.It demonstrates that the absorption coefficient of GaSe∶ Ag(≤0.04%,mass percent) crystal is twice that of a pure GeSe,and the CO2 laser Second Harmonic Generation(SHG) efficiency is about 1.7 times that of ZnGeP2 crystal.