Abstract

Analyses of Q-switched Nd³⁺ lasers on the 1.06-µm ⁴F_3/2—⁴/_11/2 transition often assume the ⁴/_11/2 lifetime is zero, but this a poor assumption because even the lowest estimate for this lifetime¹ of 10 ns in Nd:YAG Is of the same timescale as typical Q-switched pulses. In models which have included finite lower laser level relaxation time, Boltzmann occupation factors of the upper and lower laser levels relative to their total manifold populations have not been taken into consideration.² A model has been developed for homogeneously broadened Q-switched Nd³⁺ lasers, which includes finite lower laser level relaxation time and Boltzmann occupation factors. The model Indicates that extraction efficiency, which is the fraction of the upper manifold population that becomes stimulated photons, depends on the number of times above threshold, the ratio of the lower laser level to cavity lifetime, and the Boltzmann occupation factors of the lower and upper laser levels. Using the model for the 1.064-μm Nd:YAG transition, a maximum reduction of 32% In extraction efficiency, relative to the case of a lower level lifetime of zero, is predicted.

© 1988 Optical Society of America