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Diplo ma thesis abstract. "Genera tion and d etection THz pulses in thick crystals" Makarova S. A. Naza rov M. M.
In this work we p resent researches of generation and d etection of THz radiation b y femto second pulses in electro-op tical crystals ZnTe and GaP. The co herent pico second u ltrashort pulses of terahertz rad iatio n are generated b y optical rectification and detection based on electro -op tical effect. These effects both d epend o n qu ad ratic nonlinearit y, laser pulse duratio n and p hase synchro nism. We investigate how efficienc y of generatio n and detection of THz depends o n laser pu lse p arameters (wavelength, sp ectral width, pulse du ration) and crystal's p arameters (thickness, refraction and ab so rption). We fou nd that mo del of THz spectrum which well agrees with experiments and allows to analyze influence of each parameter. In this work we present quantitative estimations o f significant parameters. The measured refraction and absorptio n sp ectra in THz range are well described b y Lorenz mod el. The insufficiently kno wn case whe n thick crystals are u sed for increase signal - noise ratio in requ ired THz range. Taking into acco unt changes of pu lse du ration in crystal is the new metho d in research of generation and d etectio n THz rad iation. Obtained mod el of generatio n and detection co nsid ers d iffusio n o f laser pu lse in thick crystal. We fou nd that the u se of laser pu lse with large chirp increases efficienc y o f generatio n THz radiation in t hick cr ystals. Moreover we p ropose the u se o f the structure consists o f bo th crystals GaP and ZnTe as a d etector of THz pulse. We fou nd that this stru cture cou ld increase frequ ency range of THz sp ectro meter. These results allow finding op timal set of parameters, when sensitiveness o f THz spectrometer is maximum in requ ired THz range. Wid th of THz sp ectru m and frequency of maximum efficienc y THz spectrometer are changed b y mo dificatio ns o f wavelength, crystal thickness and laser pu lse duratio n.