Generation Of Narrow-band THz Radiation Based On The Stimulated Raman Effect With GaAs Crystal And Theoretical Study On A Novel Method Of THz Detection

Owing to its major features, and its application prospect in spectrograph, materials science, biology, medicine, communication, and on national defense, the terahertz technology has attracted particular interest. And the development of THz photonics is based on the development of THz sources and THz detection method. The main content and innovative points in the dissertation can be summarized as follows:1. The influence of two-photon absorption in GaAs crystal was studied and analyzed based on the multiphoton theory, which was suggested by Wherrett. The change in dispersion character of GaAs crystal was derived in the case of presence of pump-induced two-photon absorption. And the influence of it on the self-focusing effect also was analyzed in theory.2. According to the theory of stimulated Raman scattering, the influence of pump intensity on the plasmon vibration was analyzed based on the equations of electronic polarization, the normalized lattice displacement and the plasmon density in the time domain in theory. The numerical simulations of lattice vibration in time and frequency domain and the change of refractive index and absorption induced by plasma were carried out. The angular tuning character of Stokes wave is also numerically simulated.3. The time domain characters of intracavity pump intensity, signal intensity, and idler intensity were investigated in theory. The threshold pump intensity for an electric-optical Q-switched doubly resonant IOPO was derived firstly, and numerical simulation was carried out. The result provide a theoretical basis for the electric-optical Q-switched DIOPO experimental research. The near-degenerate DIOPO was investigated in experiment. The wavelength tuning character and spectral character of signal and idler beams and conversion efficient were studied experimentally. The result obtained in experiment had a well coincidence with numerical result. In the case of repetition frequency equal to 10Hz, the total output intensity of signal and idler wave was equal to 60.7mJ with pulse width of 6.2ns.4. The tunable THz generation in single GaAs crystal based on its stimulated Raman effect was obtained in experiment. The result proved that, based on the LO phonon-plasma interaction, the tunable THz radiation could be obtained with change of pump intensity. The tuning character of THz frequency with pump intensity was obtained in experiment. The tuning range of THz range is 0.9~3THz with 10.5~30.5mJ pump energy and pump wavelength 2284nm.5. The possibility of tunable THz detection in Fresnel phase-matching GaAs crystal was investigated in theory firstly. Angular tuning character of frequency- upconversion wave was simulated in theory. The influence of Goos-Hanchen shift, surface roughness, the full width at half maximum (FWHM) acceptance bandwidth for internal total internal reflection angle, the effective nonlinear coefficient and the crystal absorption on frequency upconversion were investigated in theory. The frequency-upconversion efficient and output intensity were derived firstly in the case that the crystal absorption in THz range can not be ignored. For a better understanding of the situation, the zigzag propagation is schematized on a straight line. And a designed experiment was also suggested. The calculated results provided a sound theoretical basis for tunable THz wave detector in Fresnel phase matching scenario.