Passive Q-switching of an erbium-doped glass laser by using a Co2+ : ZnSe crystal

The operation of a passively Q-switched laser emitting the TEM_mn mode is described. The excited-state absorption losses and nonlinear absorption in the shaded ends of the active element are taken into account. We measured the laser pulse energy for the TEM₀₀ mode, the ratios of the output energy in transverse TEM_mn modes with m = 0 – 4, n = 0 and m = 0 – 3, n = 1 to the TEM₀₀ mode energy in an erbium-doped glass laser and determined its temporal parameters in the passive Q-switching regime achieved with the help of a Co²⁺ : ZnSe crystal. It is shown that on passing from one type of the transverse mode to another for invariable parameters of the resonator, the laser pulse energy changes discretely. A change in the radius of the transverse distribution of the TEM₀₀ mode at the output mirror of the passively Q-switched laser during the development of lasing is estimated. It is found that the relative change in the laser beam cross section on the output mirror under our conditions is less than 2%. The experimental data obtained in the study are in good agreement with our calculations.