Broadband semiconductor terahertz laser based on heterogeneous cascades

We present a development of a broad gain heterogeneous quantum cascade laser for terahertz frequencies. By placing appropriate different active-regions based on a four-quantum-well design into a double-metal waveguide we obtained laser emitting gapless over a bandwidth of 1 THz, between 3.2 to 2.2 THz. This means that this single-device source covers an emission range of nearly 40 % around the center frequency. In pulsed mode operation, our devices show threshold current density as low as 285 A/cm2 and they operate up to 125 K. We also report on continuous wave measurements. © 2011 SPIE