Optimization of end-pumped, actively Q-switched quasi-III-level lasers

Abstract

The new model of end-pumped quasi-III-level laser considering transient pumping processes, ground-state-depletion and up-conversion effects was developed. The model consists of two parts: pumping stage and Q-switched part, which can be separated in a case of active Q-switching regime. For pumping stage the semi-analytical model was developed, enabling the calculations for final occupation of upper laser level for given pump power and duration, spatial profile of pump beam, length and dopant level of gain medium. For quasi-stationary inversion, the optimization procedure of Q-switching regime based on Lagrange multiplier technique was developed. The new approach for optimization of CW regime of quasi-three-level lasers was developed to optimize the Q-switched lasers operating with high repetition rates. Both methods of optimizations enable calculation of optimal absorbance of gain medium and output losses for given pump rate.

Diode-side-pumped, passively Q-switched Yb:LuAG laser

“…Assuming a quasi-stationary pumping condition (see details in [22]), a qualitative model for estimation of the inversion, gain profiles, internal fluency and stored energy was elaborated. A typical 2D image of a gain profile (cross-section of the side-pumped active medium) truncated to laser mode is shown in Fig.…”

The new optimization method of Q-switched quasi-three-level lasers

“…To analyze these effects the semi-analytical model was derived 28 , which enables estimations of relative occupation y 2 = N 2 /N tot of upper laser level where N 2 -occupation of upper laser level, N tot -dopant concentration. In the model ground state depletion, up-conversion, pump saturation where taken into account.…”

“…For definite initial gain (i.e. definite values of pump density, pump duration and gain medium length) the modified Degnan's method can be adopted 9,19,26,28 for optimization. Let us notice, that initial population Δy 2,i is a function of pump power P 0 and pump duration t pump .…”

Space-dependent modeling of diode-pumped actively Q-switched lasers with considering lower level lifetime

“…The Modeling and optimization of diode-pumped Q-switched laser has attracted much attention [1][2][3][4][5][6] due to a wide variety of its applications in civil, military and scientific research fields [7][8][9][10][11][12]. With the expansion of application range, the more accurate modeling of the laser is required.…”