Maximum value of the pulse energy of a passively Q-switched laser as a function of the pump power

Abstract

The finite recovery time $T_s$ of the bleached absorber is presented as one of the possible mechanisms accounting for the increase–maximum–decrease in pulse energy E with the pumping rate $W_P$ in cw-pumped passively Q-switched solid-state lasers, by analytically evaluating the sign of the derivative $\partial E/\partial W_P$. The results show that, in the low pump regime ($T>T_s$, T is the interpulse period), the initial population density $n_i$ remains constant, the final population density $n_f$ decreases with $W_P$, and this results in a monotonic increase of E with $W_P$. In the high pump regime $\left(T<T_s\right)$, $n_i$ decreases but $n_f$ remains the same with $W_P$; this results in a monotonic decrease of E with $W_P$. At the critical region $\left(T\approx T_s\right)$, E reaches its maximum value. A cw-pumped $\text{Yb:YAG}$ laser passively Q switched by a ${\text{Cr}}^{\text{4+}}:\text{YAG}$ absorber is demonstrated to confirm this model. The theoretical model is also applied to the analysis of three previously reported passive Q switching solid-state [$\text{Nd}:{\text{GdVO}}_{\text{4}}$, ${\mathrm{Nd}}^{+}:\mathrm{La}{\mathrm{Sc}}_3{\left({\mathrm{BO}}_3\right)}_4({\mathrm{Nd}}^{+}:\mathrm{LSB})$, and $\text{Nd}:\text{YAG}$] lasers experiments.

© 2006 Optical Society of America

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