Raman Multiplier Yellow Laser

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 methods to generate new laser lines, and can realize the compact, all-solid-state Raman lasers, which have important applications in various fields.This thesis presents systemic characteristics of the Raman laser based on the KGd(WO₄)₂ and the yellow laser based on the self-Raman conversion of Nd:YVO₄ and the intracavity frequency doubling using KTP.Based on the different characteristics of the Raman media, KGd(WO₄)₂ was chosen to form an extracavity Raman laser, the dependence of the output power on the polarization direction and power of the pump light were studied experimentally.The optical properties of the frequency doubling crystals were introduced, the phase matching angle and the second-order effective nonlinear coefficient was calculated based on the KTP type II phase matching under the first stokes wavelength of 1178nm.Based on the optical transmission matrix, the LD output properties and the coupling system were investigated. The method of determining the Gaussian beam waist radius and the position after the coupling system was given. The reasons and the results of the thermal lens were analyzed. The focal length of the thermal lens was measured experimentally. The influence of the thermal lens on the cavity mode was considered. The cavity mode radius was calculated with the consideration of the thermal lens in the laser cavity.The rate equations of the intracavity frequency-doubled self-Raman laser were deduced with the considerations of the Raman conversion, frequency-doubling conversion and the thermal diffraction loss. The output pulses of the Raman and the yellow laser were simulated.The LD pumped c-cut Nd:YVO₄ self-Raman intracavity frequency doubled yellow laser was first achieved. The output characteristics of the yellow laser were analyzed, including the fundamental pulses, the power and the time properties of the first stokes and the yellow laser pulses under different Q switching frequencies. The average output power of 589.4nm was 151mW when the pump power was 7.56W and the Q switching frequency was 15kHz.