Widely tunable room-temperature quantum-cascade laser sources in the sub-THz to THz frequency range

We present versatile low-frequency quantum cascade laser sources that boast broad tunability by leveraging intra-cavity difference frequency mixing. By utilizing dual-upper-state active regions, which have been wavefunction-engineered for optimal performance, these devices exhibit significant advancements in their capabilities. As a result, they are now capable of producing terahertz radiation in the sub-THz to THz frequency range. A device has been observed to operate at a frequency of 231 GHz, which is the lowest reported operating frequency for room-temperature QCL sources. The feasibility of continuous-wave operation at room temperature will also be discussed.