In 1950, Motz proposed the basic structure of the device which makes it possible, but it was not until 1971  that Madey gave a full quantum-mechanical description.
In 1950, Motz proposed the basic structure of the device which makes it possible, but it was not until 1971  that Madey gave a full quantum-mechanical description. Unlike its more famous counterpart, the tunability of this device is limited only by the phase matching condition between the active medium and the magnetic field. The equivalent of population inversion is accomplished by a beam, and the radiation is produced when the beam particles interact with a static magnetic field. FTP, identify this type of laser, which derives its name from the fact that the lasing medium is a beam of unattached, negatively charged particles.
In 1950, Motz proposed the basic structure of the device which makes it possible, but it was not until 1971  that Madey gave a full quantum-mechanical description.
free electron laser (or FEL)