Mid-Infrared Quantum Cascade Lasers With Nonuniformly Tapered Waveguides

In this paper, we present a theoretical and experimental analysis of mid-infrared (4.7 μm) quantum cascade laser waveguides with different taper waveguides geometries: linear, convex, and concave tapers. We have calculated and measured brightness of the optical beam and maximal power density on the laser front mirror for different widths and lengths of the taper. Convex geometry shows the best performance and the highest powers were obtained.