Abstract
Nowadays the research and application of THz are more and more popular. The THz source of narrow band and high power output are becoming more and more important. The traditional method of getting a narrow band THz wave by optical parametric generation is to establish an optical parametric oscillation for signal. In this thesis, we expanded the THz parametric oscillation from the signal wave to the THz wave. As it is known, the wavelengths of THz wave range from 30μm to 3000μm. We chose the nonlinear crystal to do the experiment because of its high nonlinear coefficient and easy accessibility. In the THz parametric generation field, the wavelengths of THz range from 100μm to 300μm. Additionally, according to the phase matching condition for the nonlinear optics process, there is a 65 degree angle between the THz wave and pump light. In general, this walk-off effect is bad for the THz research; however we combine this effect with the grating effect to establish a y-surface reflection distributed feed-back THz parametric oscillation crystal. The grating is fabricated on the surface by the mechanical method of laser cutting. According to the transmittance effect of grating, we measured the THz wave in the vertical direction to the surface grating, which verifies our design. The narrow band THz can be measured by detecting the THz power in different angles because of the transmittance grating effect. The THz bandwidth is about 18 μm in wavelength or 0.19 THz in frequency. Correspondingly, the pump wavelength is 1064.36 nm and the signal wavelength is 1071.21 nm with a 0.6-nm FWHM bandwidth.