PROBLEM TO BE SOLVED: To set a device, which realizes unidirectional amplification of light by amplification using electron in vacuum as an electron-tube type unidirectional optical amplifier.
SOLUTION: An amplifier part 3, which amplifies light in one direction by utilizing an electron gun 2 and an electron beam 1 from the electron gun 2, is arranged in vacuum. The amplifier part 3 is constituted of two wave-shaped mirrors 4 and 5, which are arranged separated, so that the mirror surface distance increase toward both end parts so as to form an electron-beam travel part. In the electron beam travel direction of the amplifier part 3, light input parts 4a and 5a, optical amplifier parts 4b and 5b having the constant mirror distance, which amplify the light emitted from the light input part by utilizing the energy received from the electron beam 1, and optical output parts 4c and 5c, which output the light emitted from the optical amplifier part to the outside part, are formed sequentially. At the same time, a wave-shaped optical waveguide 6, which enlarges the number of the optical waves, is formed in a space between the wave-shaped mirrors 4 and 5.