Beam combining for high power quantum cascade laser arrays

High-power, multi-watt quantum cascade laser (QCL) arrays emitting in the mid and long-wave infrared atmospheric windows (3 to 5 μm and 8 to 12 μm, respectively) with nearly diffraction-limited beam quality will be of immediate use to several military applications, including directional infrared countermeasures (DIRCM) and laser radar (LADAR), and to several civilian applications such as trace gas sensing and free space optical communications. In Phase I of this project, we have performed detailed analysis of several different schemes for beam combining high power QCLs. We have selected two schemes for implementation. Our analysis shows that such arrays, when based on our state-of-the-art single emitter QCLs, should reach 10W continuous wave power at room temperature (CR/RT) at 4.6 μm. In Phase II of this effort, we will fabricate and characterize prototype arrays based on both Phase I designs. These arrays will form the basis for deployable laser engines with performance sufficient for immediate insertion into DIRCM systems. Furthermore, we will create the roadmap for further extending the performance of these arrays to beyond 100W.