Above room temperature continuous wave operation of a broad-area quantum-cascade laser

We describe the design and implementation of a broad-area (w ≈ 30 μm) quantum-cascade laser operating in a continuous wave mode up to heat-sink temperatures beyond +100  °C. The room-temperature emission wavelength is 4.6 μm. The temperature gradient in the active region of such a wide laser stripe is essentially perpendicular to theepitaxial layers and the resulting steady-state active region temperature offset scales approximately with the square of the number of cascades. With only 10 cascades in the active region, the threshold electrical power density in the current quantum-cascade laser in the continuous-wave mode is as low asVth × Ith = 3.8 V × 0.9 kA/cm2  =  3.4 kW/cm2 at room temperature for 2  mm-long two-side high-reflectivity coated laser stripe. A 4 mm-long one-side high-reflectivity coated laser stripe delivers in continuous-wave mode above 0.6 W at +20 °C and above 1.3 W at −27 °C (cooled with a single-stage Peltier element). A 2 mm-long two-side high-reflectivity coated laser stripe demonstrates continuous-wave lasing up to at least +102 °C (375 K). The thermalconductance,Gth, ranges between 235  W/K cm2 and 140  W/K cm2 for temperatures between −33 °C and +102 °C. This demonstration opens the route for continuous-wave power scaling of quantum-cascade lasers via broad-area laser ridges.

Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: M. P. Semtsiv and W. T. Masselink Source Type: research