[摘要]：Terahertz frequency photonic-crystal quantum cascade lasers allow directional and controllable surface emission while at the same time functioning efficiently well above liquid nitrogen temperature. Through an in-depth understanding of the mechanism underlying surface emission, we demonstrate optimized devices with significantly reduced absolute threshold currents. We are able to reduce the device surface area by more than a factor of two, while maintaining angularly narrow, single-lobed surface emission with a divergence of approximate to 10 degrees X 10 degrees. The devices emit at similar to 2.8-2.9 THz, with maximum operating temperatures in the range 80-150 K. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3489941]
