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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 high efficiencies 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.