Modeling for Spatial Overlap Effect of End-Pumped Passively Q-Switched Nd:YVO4/Cr4+:YAG Laser and Its Experimental Verification

In this work, the spatial effects of the pumping and lasing were considered into the coupled rate equations of passively Q-switched lasers for the condition of no saturation in the gain medium. A transcendental equation of energy utilization was derived, and the solution to the equation was approximated by an analytic model developed in previous work. The reflection factor of output coupler with low reflectivity was modified for more accurate output energy evaluations. Experimentally, an end-pumped Nd:YVO4/Cr4+:YAG laser in a concave-plano cavity with output coupling reflectivity ranging from 10% to 92% was demonstrated, and two different pumping spot sizes of laser diode were adopted for validating the developed spatial model. The experimental results showed good agreements with the theoretical calculations.