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.Index Terms-Birefringent filter (BRF), continuous tuning, high-power laser, InGaAs, optically pumped semiconductor disk laser (OP-SDL), vertical-external-cavity surface-emitting laser (VECSEL).

We report on single-mode distributed-feedback quantum cascade lasers emitting at 4.8 μm with continuous-wave threshold power consumption as low as 0.76 W at 20 °C and 0.98 W at 50 °C. Following growth of the laser active region and semiconductor cladding layers by a single molecular beam epitaxy process, devices with 4-μm-wide ridges and vertical sidewall gratings were fabricated using plasma etching and standard dielectric and metal deposition processes. In terms of mode stability, output power, and efficiency, we show that lasers with 1-mm cavity length and high-reflectivity back-facet coatings can match the performance of buried heterostructure devices, but with the advantage of requiring only a single epitaxial growth step.

We report on the performance and reliability of laterally-coupled distributed-feedback (DFB) interband cascade lasers designed to operate at 3.6 μm wavelength. A two-step ridge etch process ensures single-transverse-mode operation with minimal lateral current spreading, and a second-order Bragg grating etched alongside the ridge waveguide imposes single-mode DFB operation. Life tests performed on four randomly selected lasers, continuously operating at 40 °C with output power >10 mW, showed no measurable degradation after each laser was operated continuously for more than 1500 h.

We demonstrate index-coupled distributed-feedback diode lasers at 2.65 µm that are capable of tuning across strong absorption lines of HDO and other isotopologues of H2O. The lasers employ InGaAsSb/AlInGaAsSb multi-quantum-well structures grown by molecular beam epitaxy on GaSb, and single-mode emission is generated using laterally coupled second-order Bragg gratings etched alongside narrow ridge waveguides. We verify near-critical coupling of the gratings by analyzing the modal characteristics of lasers of different length. With an emission facet anti-reflection coating, 2-mm-long lasers exhibit a typical current threshold of 150 mA at 20 °C and are capable of emitting more than 25 mW in a single longitudinal mode, which is significantly higher than the output power reported for loss-coupled distributed-feedback lasers operating at similar wavelengths.