A Unidirectional Traveling-Wave Optical Maser

Net gain at optical frequencies was demonstrated by the successful operation of maser oscillators. 1,2 The first direct measurements of gain at optical frequencies were made by Javan, Bennett and Balik 3 for the helium-neon gas maser and by Kisliuk and Boyle4 in a ruby solid state maser. The optical amplifiers described by these investigators were lowgain devices. Since at optical frequencies the maser is the only available amplifier which at present preserves amplitude and phase information, it may well have to provide extremely high stable gains of between 30-60 db in many applications, as for example in an optical communications system. It is well known that to realize a stable high-gain amplifier it is essential to make the amplifier nonreciprocal. This has been accomplished in the case of the microwave traveling-wave maser 5 but has not previously been reported at optical frequencies. The objective of this paper is to discuss the basic principles which are necessary for realizing a nonreciprocal optical amplifier and to report the successful operation of a pulsed unidirectional traveling-wave optical maser (TWOM) using ruby. Also the image amplifying ability of the TWOM is discussed and demonstrated. * This work was supported in p a r t by the U. S. Army Signal Corps under Cont r a c t D A-36-039-sc-87340. 1371