Optimization of a Broadband Gain Element for a Widely Tunable High-Power Semiconductor Disk Laser

The layer structure of the gain element in an optically pumped semiconductor disk laser was parametrically optimized with respect to a target function specifying a desired unsaturated reflectance over a desired wavelength range at a constant pump intensity. Spectral threshold pump intensity measurements confirmed the efficacy of the design, showing a much wider low-threshold regime than a conventional nonbroadband gain element, in good agreement with simulations. This evaluation avoids the possible influence of additional factors under high-power operation. Nonetheless, having a high and nearly constant broadband unsaturated reflectance at low pump intensity is a key to obtain good high-power performance, as evidenced by the obtained continuous tuning from 967 to 1010 nm with a maximum output power of 2.6 W.