A simple quasi-optical design for LO coupling at THz bands

A simple quasi-optical design for LO coupling in the quasi-optical heterodyne system has been described. Due to the limited LO power available at THz bands, it is of great importance to achieve high efficiency LO power coupling to the mixer. Two elliptical mirror have been employed to couple the LO power to the SIS mixer. Measurement at nearly 500GHz shows such configuration is sufficient to pump a long junction SIS mixer.