A relativistic electron beam propagating near a dielectric film will produce Cherenkov radiation. The beam couples most strongly to the axial component of the guided modes, and the strength of the coupling is determined by the evanescence of the wave. The characteristic scale length for this evanescence is ~λβγ/2 π, where λ is the wavelength of the radiation and β and γ are, respectively, the relative velocity and relative energy of the beam electrons.

© 1984 Optical Society of America

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