## Abstract

By considering the single-photon absorption and two-photon absorption processes in the GaAs saturable absorber, the coupled rate equations for a diode-pumped passively *Q*-switched and mode-locked (QML) laser with GaAs coupler under Gaussian approximation are given. These rate equations are solved numerically. The key parameters of an optimally coupled passively QML laser with the shortest pulse-width envelope are determined. These key parameters include the parameters of the gain medium, the saturable absorber, and the resonator, which can minimize the pulse-width of a singly *Q*-switched envelope. Sample calculations for a diode-pumped passively *Q*-switched mode-locked *c*-cut $\mathrm{Nd}\text{:}{\mathrm{GdVO}}_{4}$ laser with a GaAs coupler are presented to demonstrate that the shortest pulse-width envelope can be obtained by selecting the optimal small-signal transmission of the saturable absorber and the reflectivity of the output mirror.

© 2011 Optical Society of America

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