Modeling of Passive Q-Switched Yb, Er Glass Lasers with Transverse Pumping by Linear Laser Diode Arrays

A mathematical model of a passively Q-switched solid-state laser based on ytterbium and erbium codoped active media with transverse pumping by linear laser diode arrays has been developed. The gain in the laser is calculated using rate equations taking into account the space-time dependence of the pump radiation intensity in the laser element. The output laser characteristics, the pulse energy, the peak pulse power and the pulse duration, are calculated using analytical equations obtained for a passively Q-switched solid-state laser in the approximation of a "slow" saturable absorber. The model allows one to find the range of parameters of the active element, passive modulator, resonator, and pumping system at which the generation threshold is reached and the laser generates pulses with the required energy and duration. Modeling results were used for the experimental development of lasers with an active element based on phosphate glass doped by ytterbium and erbium ions. The energy and duration of the output light pulses were ≈ 1 mJ, ≈ 40 ns, and ≈ 2 mJ and ≈ 20 ns, depending on the content of ytterbium and erbium ions in the active element, as well as on the initial transmission of the passive modulator and the resonator parameters.