HOT TOPIC
A New Source of THz-FIR Radiation
J. E. Walsh, J. H. Brownell, J. C. Swartz
Department of Physics and Astronomy,
Dartmouth College, Hanover, New Hampshire 03755-3528
M. F. Kimmitt
Department of Physics, Essex University, Colchester, UK
January 7, 1999
Abstract
A new source of tunable coherent radiation which operates in the THz-FIR region of the
spectrum is described. The device is based on the passage of a small diameter, moderate
current but extremely “bright” electron beam over a diffraction grating. The
beam is produced in a modified scanning electron microscope (SEM) and the grating is
mounted in the focal region of the electron beam. Unlike some earlier devices of this type
where the available output power is limited to the incoherent superposition made by
individual electrons as they move over the grating, the present source operates in a
collective mode in which the output power increases as the 4th power of the beam current.
Present performance levels are reviewed and speculations on future developments are
presented.