Dynamic measurement of gain volume fluctuation of a high power Cw Nd: YAG laser

One of the main complications for designing solid state laser systems arises from the thermal focusing of the laser rod. This thermal lensing affects substantially the resonator stability which may strongly perturbs the laser output. Resonator with an internal lens has been extensively analyzed theoretically [1,2] and different experimental configurations for optimized gain volume have been proposed [3,4]. In this work, we present a dynamical measurement of the gain volume fluctuation in a high power Cw Nd:YAG laser resonator. The refractive power (D = 1/f) of the flash lamp-pumped Nd:YAG rod was measured as a function of the total power of electrical pump and the laser oscillation power. In these experimental measurements the length of laser resonator was varied between 40 to 160 cm. The results of the gain volume fluctuation is presented versus the total power for all the tested cavity length. In all the cavity configuration, the rod position was tested for an optimized output power. A large amount of changes in the gain volume is reported for power of 1 to 7 kw. These results give a very important information for designing high power Cw Nd:YAG laser systems