AN INTERACTIVE NUMERICAL-MODEL OF DIODE-PUMPED, Q-SWITCHED CAVITY-DUMPED LASERS

We have developed an interactive numerical model, which describes the operational characteristics of multiple diode-pumped laser systems that are Q-switched or Q-switched/cavity-dumped. These are the first computer-generated results obtained using rate equations that incorporate the 'inversion reduction parameter' gamma. The quantity gamma can partially take into account effects of relaxation and thermally driven transfer, which occurs between laser level multiplets. A value of gamma near unity is found for the Nd:YAG lasers, implying considerable thermal relaxation of the lower lasing level, and it may also imply some thermal refreshing of the upper lasing level. A value of gamma = 2 is found to fit the Ti:sapphire results, indicating that the lower lasing level is not relaxed during laser pulse development. The interactive nature of the model allows for variation of all the significant parameters required to generate a Q-switched or cavity-dumped pulse. Input information is expressed in terms of standard variables such as stored energy, optical and dissipative losses and stimulated emission and pump absorption cross sections. The effects of additional parameters, including the Gaussian beam profile of the cavity, the induced losses associated with the rise and fall times of the Q-switch and cavity-dump Pockets cell, and the induced thermal lensing effects produced by the pump rate in the gain medium are taken into account. The width and energy of the cavity-dumped laser pulse can also be studied in the model by varying the cavity-dump voltage switch transition time. The model is compared with four distinctly different diode-pumped laser systems that have been developed in our laboratory during the past year and its predictive capability is evaluated. In its present form, the model is being used as a tool in the design of new solid state diode-pumped lasers.