All Solid-state Raman Laser Theory And Experimental Research

Stimulated Raman scattering (SRS) can shift the laser frequency over a fixed frequency gap to produce new laser lines. The laser spectrum reachable with SRS extends from ultraviolet to near infrared. SRS possesses many attractive features, i.e. beam clean-up, pulse compression, no need for phase matching, and high conversion efficiency. A good number of crystals have been found to be Raman-active, such as Ba(NO₃)₂, BaWO₄, KGd(WO₄)₂ and YVO₄ crystals. As compared with the traditional gas and liquid Raman media, the Raman crystals offer high gain, high molecule density, good thermal and mechanical properties. Presently, the SRS in crystal media is one of the most important mechanisms to generate new laser lines, and can realize the compact, all-solid-state Raman lasers, which have important applications in various fields.At present, all-solid-state Raman lasers attract intensive research interest in the field of solid-state laser and nonlinear optics. Scientists from Russia act as the leading role in the regime of Raman crystal growth and research on the solid-state Raman lasers. Researchers from America, Germany, Australia and other countries are taking part actively in the field of the all-solid-state Raman lasers. China is renowned for the advanced crystal growth technology, and recently, some Chinese institutes and companies offer the Raman media of the good quality, e.g. SrWO₄, PbWO₄, BaWO₄, and Nd:KGd(WO₄)₂ crystals. However, the research on the solid-state Raman laser lags behind, and up to now, there has been no work on the solid-state Raman lasers reported in the Chinese Mainland.Owing to the lack of practical Raman crystals in the early years, the intensive study of the SRS in crystals just began in 1980s. There are plenty theoretical works done on the SRS processes in the gas media, and relatively little effort exerted on the theoretical work of the SRS in the crystals. The crystalline media possesses much different features to the gas counterparts, and the theoretical research on the SRS in the crystals and theories of the all-solid-state Raman lasers are the bases of the development of all-solid-state Raman lasers of high performance.This dissertation presents a full and systematic theoretical and experimental study on the characteristics of the extracavity, intracavity, and self-Raman lasers with KGd(WO₄)2, SrWO₄ and Nd:YVO₄ crystals as the Raman media. The main content of this dissertation is as follows1. Based on the wave equation and SRS material equations, and with up to the third Stokes and backward Raman scattering to be considered, a new set of radiation transfer equations was deduced for the solid-state extracavity Raman lasers in the steady-state regime. The radiation transfer equations were normalized, and the numerical method was given. The numerical results of the radiation transfer equations were in good agreement with the experimental ones.2. As an approximate and simplified theoretical model, the rate equations of the extracavity...