Multi-wavelength operation and vertical emission in THz quantum-cascade lasers

Multi-wavelength laser action in the terahertz (THz) region from a quantum cascade structure is demonstrated. Laser emission is obtained at 1.39 and 2.3 THz by using a structure based on a large single quantum well. A strong perpendicular magnetic field is employed to increase the gain and achieve laser action. In the second part of the work, a vertically emitting THz quantum cascade laser device that exploits an in-plane optical resonator based on a two-dimensional photonic crystal is demonstrated. Stable single mode vertical emission is reported. Simulations based on the block-iterative frequency-domain method on a plane wave basis account for the observed results.