Tunable room temperature solid state THz source based on Smith-Purcell radiation

This paper presents the theory and design of a novel, low-power, compact, room-temperature, tunable, solid state THz source of Smith-Purcell radiation. The design comprises a Transferred Electron Device and a metal transmission grating separated by a high-K dielectric. When a sufficiently high electric field is applied across the cathode and anode of the device, space-charge regions (also known as dipole or Gunn domains) form within the device and propagate across it. The moving dipole domains couple to the grating electromagnetic modes thereby mimicking the bunching of electrons seen in free-electron lasers. The result is the generation of coherent Smith-Purcell radiation that is tunable via adjusting the voltage applied across the device. The design is scalable from RF, through the THz, into the long-wave infrared via grating geometry and device material changes. Time-domain full-wave electromagnetic simulations were performed to design such a device for use in the THz region. The simulation results predict coherent emission at 1.0 THz.