Ultra-broadband heterogeneous quantum cascade laser emitting from 2.2 to 3.2 THz

We present a heterogeneous terahertz quantum cascade laser that emits continuously between 2.2 and 3.2 THz, covering an emission range of over 40% around the central frequency. Devices were realized by stacking different active region designs into a double-metal waveguide. They operate up to 125 K with 15 mW peak power at 10 K in pulsed mode. Smaller devices show broadband emission also in continuous wave. Time-resolved measurements of the emission spectra were realized, confirming the broadband emission within a 5 ns time window.