Abstract
We report low threshold InAs/AlSb quantum cascade lasers emitting near 15 micron. The devices are based on a vertical design similar to those employed previously in far infrared InAs-based QCLs, whereas the doping level of the active core is considerably decreased. The lasers exhibit a threshold current density as low as 730 A/cm(2) in pulsed mode at room temperature and can operate in this regime up to 410K. The continuous wave regime of operation has been achieved in these devices at temperatures up to 20 degrees C. The cw regime is demonstrated for InAs-based QCLs for the first time at room temperature.