Maser
Maser, a device that generates or amplifies short radio waves, called microwaves, which cannot be effectively amplified by ordinary electronic equipment. The word maser is derived from microwave amplification by stimulated emission of radiation. The operating principles of the maser are the same as those of a related device, the laser, except that the laser generates or amplifies light waves rather than microwaves.
Masers are used in astronomy and in various fields of research, especially when weak microwaves must be amplified. The first maser was produced in 1954 by Charles H. Townes of Columbia University.