Mid-infrared semiconductor lasers for power projection and sensing

The recent break-through in semiconductor laser-module technology in the infrared region between 2 µm and 10 µm opens up new windows of opportunity for active sensing, imaging, and modulated power projection. Optically pumped semiconductor disk lasers and quantum cascade lasers cover the infrared spectral range continuously, either with tuneable small bandwidths for active spectral sensing or with broad bandwidth, high power (Watt level), and good diffraction properties (M2<2) for modulated power projection and (3D) imaging. This paper reviews the physics of infrared semiconductor disk lasers and quantum cascade lasers, explains the challenges of the module technology (the next higher integration level after chip technology) and outlines several security and defence related issues for future applications.