Advanced terahertz backward wave oscillators

Calabazas Creek Research, Inc. is funded by the National Aeronautics and Space Administration to develop efficient, light-weight, backward wave oscillators (BWOs) for applications from 300 GHz to more than I THz. These devices are needed as local oscillator (LO) sources in heterodyne receivers. BWOs have broad tunability (over 100 GHz) and high output power (∼1 mW); however, existing BWOs are heavy (over 20 kg), consume a lot of power (270 W), require water cooling, and have poor output mode purity. The technical objectives of the current program are as follows: utilize advanced manufacturing techniques to extend the operating range to frequencies exceeding 1 THz; incorporate a depressed collector to improve the efficiency and eliminate water cooling; improve the output coupling to increase coupling efficiency and mode purity; and reduce the magnet system size and weight. During the Phase I program, techniques were developed to couple the power from the slow wave circuit and transform the RF wave into a purely Gaussian output mode.