被动调Q激光器速率方程

214 IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 25, NO. 2, FEBRUARY 1989

Theory of the Optimally Coupled Q-Switched Laser

JOHN J. DEGNAN

Abstract-The general equations describing Q-switched laser oper- all of the key parameters (optimum reflector, output en-

ation are transcendental in nature and require numerical solutions. ergy, extraction efficiency, pulsewidth, peak external and

This greatly complicates the optimization of real devices. In this paper,

we demonstrate that, using the mathematical technique of Lagrange internal powers, etc.) which describe the optimally cou-

multipliers, one can derive simple analytic expressions for all of the pled laser. The aforementioned optimized laser parame-

key parameters of the optimally coupled laser, i.e., one which uses an ters can be expressed as functions of a single dimension-

optimum reflector to obtain maximum laser efficiency for a given pump less variable 2 , defined as the ratio of the unsaturated

level. These parameters (which include the optimum reflectivity, out- logarithmic small-signal gain to the dissipative (nonuse-

put energy, extraction efficiency, pulsewidth, peak power, etc.) can all

ful) optical loss, multiplied by a few simple and easily

he expressed as functions of a single dimensionless variable z , defined

as the ratio of the unsaturated small-signal gain to the dissipative (non- accessible constants. In Section 111, we present several

useful) optical loss, multiplied by a few simple constants. Laser design design curves which are useful to laser design and/or the

tradeoff studies