“…Photomixers are promising continuous-wave terahertz sources as potentially compact, low-power-consuming, coherent, low-cost, and tunable sources [21]- [28]. A terahertz photomixer is a heterodyne scheme, in which output of two single-mode lasers or output modes of a dual-mode laser with their frequency difference falling in the terahertz range mix in a nonlinear medium, such as a photoconductor [27], [29] or a superconductor [30], and generate a signal, whose frequency is equal to the frequency difference of the two lasers or two modes of the dual-mode laser.…”