Continuous-wave operation of broad-area mid-infrared quantum cascade lasers for high brightness

摘要

Summary form only given. For a number of applications, high average power in the mid-infrared (MIR) part of the spectrum is required from a compact laser. The quantum-cascade laser (QCL) emitting in the mid-infrared region of 4 to 8 μm has been refined to the point that its internal quantum efficiency is approaching fundamental limits. QCLs designed for power typically contain 30-40 cascades, are less than two wavelengths in width, and laser ridge lengths are typically between 3 and 6 mm. Because the overall efficiency of QCLs is less than 25%, the thermal management in high-power QCLs is critical and generally requires narrow ridges with re-grown InP abutting them. The narrow ridges also result in nearly diffraction-limited emission, allowing the power to result in high brightness. The limited ridge width, however, also results a limited emission power [1]. In this paper, we demonstrate that the most power can be obtained from broad-area QCLs with limited number of cascades. Furthermore, such ultimate-power lasers can deliver good beam quality and excellent brightness. A demonstration at 4.6 μm is presented and discussed.