The Applications Of Stimulated Raman Scattering Vibrational Modes In Crystalline Media

Nowadays, stimulated Raman scattering?SRS? is an importantmethodto produce the new laser lines in crystal. The laser spectrum can be widened largely. Because of the advantages of pulse compression, beam clean-up and high conversion efficiency, SRS has important applications in various fields. With emergence of excellent Raman crystals, the SRS in crystal media is one of the most important mechanisms to realize all-solid-state Raman laser. All-solid-state Raman laser have a great value in national defense, agriculture, medicine and transportation. Crystals based on SRS can realize to enlarge laser spectrum, generate new laser lines and achieve all-solid-state Raman lasers suchas PbWO₄ Ramanlasersand SrWO₄ Ramanlasers.Firstly, the general way of generating THz based on stimulated Raman scattering is introduced.Studies have shown that THz is based on stimulated Raman scattering of phonon polariton. On the basis of Huang Kun equation, the dispersion equation of phonon polariton in crystal is derived and the dispersion curve is analyzed closely. The wave equations and wave coupling equations are used to calculate the gain equation of THz. At the same time, it is said that various parameters can affect theoutputof THz. Gainequationof THzis modelednumerical.Secondly, a laser-diode-pumped passively Q-switched intracavity PbWO₄ Raman laser is demonstrated. Up to now, the passively Q-switched intracavity PbWO₄ Raman laser was still seldom studied. This paper can study closely on experiments of PbWO₄ Raman laser. A simple structure is used in the experiment. Lots of factors can influence the output of fundamental laser and Raman laser. In this paper, we mainly study the effects of the cavity length, reflectivity of output mirror and the initial transmission of saturable absorber. When the incident pump power is 4.6 W, a maximum average output power of 375 mW is obtained, corresponding to the maximum pulse repetition is 30 kHz, and the minimum pulse width is 6 ns, and an overall diode-stokes conversion efficiencyis 8.19%.Finally, we introduce a laser-diode-pumped passively Q-switched intracavity SrWO₄ Raman laser. A simple structure is used in the experiment. Lots of factors such as cavity length, reflectivity of input mirror, reflectivity of output mirror, and initial transmission of saturable absorber can influence the output of fundamental laser and Raman laser. The difference between PbWO₄ Ramanlaser and SrWO₄ Raman laser is introduced. A maximum average output power of 724 mW is obtained at an incident pump power of 4.1 W, corresponding to an overall pump light-first-order Stokes conversion efficiency of 17.6 %. The pulse width is 8 ns, pulse repetition is 27 kHz, pulse energy is 26.8 mJ, and pulse peak power is 3.35 kW. The obtained diode-to-Stokes conversion efficiency is much higher than those of previously reported diode-pumped passively Q-switched intracavity Ramanlasers.