Frequency tuning of terahertz quantum-cascade lasers by spatially controlled optical excitation

We demonstrate the feasibility of wideband frequency tuning of terahertz quantum-cascade lasers by spatially well-controlled near-infrared optical excitation. We observe a single-mode continuous-wave frequency coverage of up to 40 GHz for a 3.1 THz laser. This represents a tenfold improvement of the tuning range for the same device as compared to tuning by current. This method is applicable to a wide variety of existing terahertz quantum-cascade lasers