High-Temperature Operation of 8.5μm Distributed Feedback Quantum Cascade Lasers

We present a distributed feedback quantum cascade laser (DFB-QCL) emitting at a wavelength of 8.5μm and operating up to 420K (147°C) with a low-threshold current density in pulsed mode. The DFB-QCLs studied are based on a four-well active design; the central portion of the waveguide consists of 60 periods of lattice matched InP-based InGaAs/AlInAs. In the design of the device, an active structure with lower doping and a deep-top grating process are utilized to achieve high temperature operation with a lower-threshold current density. At 420K, a low-threshold current density of 3.28kA/cm² and a single mode peak power of 15mW are achieved on an epilayer-up mounting device with ridge width of 26μm and cavity length of 3.0mm. A side mode suppression ratio of 25dB at 420K is obtained.