Werner Späth

8-W high-efficiency continuous-wave semiconductor disk laser at 1000 nm

We demonstrate more than 8-W continuous-wave output power with good beam quality (M2<1.8) from an optically pumped semiconductor disk laser. The combination of low threshold density of 470 W/cm2 and high differential efficiency of 60% results in an optical-to-optical conversion efficiency of 46% for this high output level. Good epitaxial quality and low thermal resistance allow the scaling of output power with pump spot area.

High-efficiency high-power semiconductor disc laser

High efficiency, high power and excellent beam quality has been achieved in optically-pumped semiconductor disc lasers (OPS-disc laser) emitting at 1000nm. Minimizing the thermal resistance between active region and heat-sink, more than 5.5W of continuous wave (cw) output has been obtained at room-temperature. Even more remarkable, the laser characteristics corresponding to this power display differential efficiencies of better than 50% and optical conversion efficiencies of better than 40%. This combination of high power and high efficiency represents the best reported values so far. As such, a highly efficient beam converter has been realized, transforming low-brightness optical pump power into high-brightness laser emission.

Multiwatt semiconductor disk lasers for near-infrared wavelengths

Optically-pumped semiconductor disk lasers offer high output power in combination with good beam quality. By optimizing epitaxial quality as well as thermal resistance, we have demonstrated more than 8W of continuous-wave, room-temperature emission at 1000nm. These high power-levels are tied to high optical-conversion efficiencies of more than 40%. Whereas available wavelengths for solid-state disk lasers are restricted to a set of atomic transitions, semiconductor disk lasers can be conveniently tailored to meet almost any wavelength. Building upon the high-power results at 1000nm, we have extended the emission range towards 900nm as well as 1100nm. Two prominent examples are devices realized at 920nm and 1040nm, in each case demonstrating several Watts of laser output.

Modeling and Experimental Result Analysis for High Power VECSELs

We present a comparison of experimental and microscopically based model results for optically pumped vertical external cavity surface emitting semiconductor lasers. The quantum well gain model is based on a quantitative ab-initio approach that allows calculation of a complex material susceptibility dependence on the wavelength, carrier density and lattice temperature. The gain model is coupled to the macroscopic thermal transport, spatially resolved in both the radial and longitudinal directions, with temperature and carrier density dependent pump absorption. The radial distribution of the refractive index and gain due to temperature variation are computed. Thermal managment issues, highlighted by the experimental data, are discussed. Experimental results indicate a critical dependence of the input power, at which thermal roll-over occurs, on the thermal resistance of the device. This requires minimization of the substrate thickness and optimization of the design and placement of the heatsink. Dependence of the model results on the radiative and non-radiative carrier recombination lifetimes and cavity losses are evaluated.