An intense short laser pulse or a millimetre wave propagating through
a
plasma channel may act as a wiggler for the generation of shorter wavelengths.
When
a relativistic electron beam is launched into the channel from the opposite
direction, the laser radiation is Compton/Raman backscattered to produce
coherent radiation at shorter wavelengths. The scheme, however, requires
a
superior beam quality with energy spread less than 1% in the Raman regime.
Specific Electrodynamical Features of a Plasma Channel Created in Gas by Powerful Femtosecond UV Laser Pulse - Application to the Problem of Guiding and Amplification of Microwave Radiation