Investigations on Transverse-Mode Competition and Beam Quality Modeling in End-Pumped Lasers

The transverse-mode competition and beam quality modeling in scaling fiber-coupled laser diode (LD) end-pumped lasers to higher power and better beam quality have been investigated with the space-dependent multimode rate equations by including the thermal effect. The total photon number and threshold of the pumping rate for each mode in the cavity were obtained by solving these equations with an iterative method, and so the threshold of the pumping power, output power, optical and slope efficiency of the single mode and laser could all be calculated. Several lasers, including one ideal laser, one multimode laser, one quasi-fundamental mode laser with folded structure, were brought forward to demonstrate the modeling process and investigate the transverse-mode competition process. The calculated results were compared with the experimental ones and the rationality of the model built in this paper was validated. The model presented here may serve as the designing guideline for a practical laser, especially one with beam quality requirement.