Abstract

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.

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