Generation of coherent terahertz radiation by photomixing of dual-mode lasers

We have reviewed and discussed the generation of continuous-wave terahertz radiation by the photomixing of dual-mode lasers, which includes a multi-mo de laser diode (LD), a dual-mode microchip laser, a monolithic dual-mode DB R LD, and a widely tunable dual-mode external cavity LD. It is demonstrated by several experiments that the beat frequency of a dual-mode laser is mor e stable than the original laser modes because of the common-mode rejection effect. We also suggest a novel scheme by which the optical beat is stabil ized to less than 1 kHz and its frequency can be precisely determined as we ll.