Low-frequency Terahertz Generation based on High-Power Quantum Cascade Lasers Emitting at λ ~ 14 μm

Authors present low-frequency terahertz generation from difference-frequency terahertz quantum cascade laser sources. In order to obtain higher nonlinear susceptibility in low frequency region, we design a long wavelength dual-upper-state active region in which transition dipole moments are increased. A fabricated device with distributed feedback grating demonstrates a THz peak output power of 20 μW at room temperature, with multi-mode THz emission at a frequency of 1.1 THz. In addition, the device produces a THz output power of 267 μW at 110 K at 1.5 THz, which is comparable to the power of low-frequency (1.2-1.6 THz) THz-QCLs at liquid helium temperature.