REPUBLIC OF SERBIA

MINISTRY OF DEFENCE

www.mod.gov.rs

MINISTRY OF DEFENCE

Material Resources Sector

Defensive Technologies Department

Military Technical Institute

www.vti.mod.gov.rs

MATHEMATICAL MODEL FOR PARAMETER ANALYSIS OF PASSIVELY Q-SWITCHED Nd:YAG LASERS

mirjana Nikolić

Military Technical Institute, Belgrade, mystastya@sezampro.rs

Željko Vukobrat

Military Technical Institute, Belgrade

Abstract: For the passively Q-switched solid state laser, the initial population density in the gain medium does not depend on the pump rate as in case of active Q-switching. The initial population density in the gain medium for passive Q-switching is determined by the initial transmission of the saturable absorber and the reflectivity of the output mirror. The numerical simulation based on ESA (excited state absorption) effect was performed. From the wide variety of passively Q-switched lasers general theories, we choosed a second-threshold approach, numerical fitting procedure and optimization method, in order to determine the output pulse energy as function of the initial transmission of the saturable absorber and the reflectivity of the output coupler. The example of modeling of solid state flashlamp pumped Nd:YAG laser with Cr⁴⁺:YAG as a saturable absorber is explained and examined to illustrate the use of the present model. The present mathematical model provides a straightforward procedure for the design of passively Q-switched solid state lasers.

Keywords: solid state lasers, Nd:YAG lasers, passive Q-switching, saturable absorbers, excited state absorption effect.