Principle of Operation
TeraHertz electromagnetic radiation is produced in this free electron
laser using an effect first explained by S.J. Smith and E.M. Purcell
in 1953. The Smith-Purcell effect describes “Visible Light
from Localized Surface Charges Moving Across a Grating”.
This effect occurs over a broad range of spectral wavelengths,
including visible through millimeter wavelengths.
The output wavelength is a function of a combination of factors.
In the devices operating at Vermont Photonics, a change the electron
beam voltage allows continuous tuning of the THz output wavelength
from100 to 1000 microns.
This device directly couples free-streaming electrons at the
grating into electromagnetic radiation. This promises very
as compared to other schemes to produce THz.
This same coupling of free-streaming electrons into electromagnetic
radiation is what makes the Klystron so successful at emitting
very high power at longer wavelengths for the microwave industry.