The Amplification Characteristics Of Raman Laser Pulse

Stimulated Raman scattering (SRS) is a fairly effective way to shift the frequency of laser. The frequencies of Raman lasers are determined by both the pump laser frequencies and the Raman materials. There are many kinds of Raman materials in all three states of materials, solid, liuquid, and gas. The spectrum of Raman laser ranges from ultraviolet to near-infrared. Besides, stimulated Raman scattering has plenty of excellent characteristics, such as good quality of scattering light, narrow pulse width, high convertion efficiency, without requiring phase matching. So, researches in Raman materials are always on the frontier of science as early as 60's in the last century. The characteristics of Raman amplifier are one of the most important aspects of Raman materials. It is a quite important job to conduct researches on Raman amplifiers.In this thesis I use YVO4 as the Raman material, studing its amplifying characteristics for Raman laser pulses and measuring its Raman gain coefficient, based on experiments in amplifying nanosecond Raman laser pulses and picosecond Raman laser pulses. The specific contents are stated as following.The Raman gain coefficient is calculated by comparing the outputs of two YVO4 crystals in different lengths under the pump of picosecond mode-locked pulses. This is the first time to obtain the Raman gain coefficient by this method to our knowledge.Both the fundamental laser and Raman laser are obtained from an end-pumped actively Q-switched self-Raman laser, using an a-cut Nd:YVO4 crystal as the laser crystal and Raman crystal. By changing the Q-switched pulse frequency and the transmission of output mirror, different output powers at the fundamental laser and Raman laser are obtained. The experiments of amplifying nanosecond Raman laser pulse are conducted under the condition that the output mirror reflectivity is 97.6% for fundamental wavelength and 93.7% for Raman wavelength and the Q-switched pulse frequency is 30 kHz.Both the fundamental laser and Raman laser are obtained from an end-pumped actively Q-switched intracavity Raman laser, using an Nd:YAG crystal as the laser crystal and an a-cut YVO4 crystal as the Raman crystal. Through changing the Q-switched pulse frequency and the transmission of output mirror, different output powers at the fundamental laser and Raman laser are obtained. In specific experiments for obtaining appropriate pulses in amplifying nanosecond Raman laser, I use output mirror whose reflectivity is 97.6%for the fundamental wavelength and 93.7%for the Raman wavelength and choose Q-switched pulse frequency of 20 kHz.