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Energy exchange between heterostructure layers by realspace electron transfer Approximate exchange energy as a functional of the electron density. Light atoms Momentum is exchanged between free electrons and light when the interaction length is limited. An analysis and a computer simulation determine the characteristics of this energy transfer. Possible experimental schemes at optical and infrared wavelengths are explored.

A tapered-wiggler free-electron-laser oscillator has been operated above threshold at the wavelength of 1.57 jum. The laser was operated with 0%, 1% , and 2% tapers in energy, achieving laser efficiency of 0.4%, 1.1%, and 1.2%, respectively. The efficiency of the 2% taper was three times the untapered case.

The first linac-based visible free-electron-laser oscillator was operated in February 1987 at a wavelength of 525 nm with and without a wiggler taper. Peak output power of 29 kW with a macropulse average power of 1.1 W was observed. The cavity dielectric mirrors were damaged at approximately 21 kW/cm2 of average intracavity power.