Among many possible applications of the extremely high brightness temperature and the radiation density obtainable with the optical maser, a high energy electron accelerator is proposed and discussed in this paper. It consists of a cylindrical tube of maser material excited by a pumping radiation through an interference filter coated on its outer surface and, it generates an oscillation in a TM0NM type mode. An optical peak power of 10 kw/cm2 was calculated to accelerate electrons by 109 ev/meter. A gas-filled cavity is proposed for velocity matching. Selection of the particular mode might be made by placing a periodically printed absorption layer on the inner surface of the maser cylinder. However, mode separation would be extremely difficult because of thermal expansion of the maser material.
Koichi Shimoda, "Proposal for an Electron Accelerator Using an Optical Maser," Appl. Opt. 1, 33-35 (1962)