After nearly two decades' development, the quantum cascade laser (QCL) has emerged from a cryogenically cooled
micro-watt emitter to room temperature continuous wave laser source with watt-level output powers. The recent
breakthroughs in the wall plug efficiency (WPE) of InP based mid-IR QCLs draws significant interest for IRCM
applications toward lower cost, weight, and overall power consumption of the system. Recent research highlight of high
power QCLs is presented, including power levels, beam quality, and reliability.