Optical amplifiers with a Resonator in which a Light pulse can do multiple round trips before being coupled out.

A regenerative amplifier is a device which is used for strong amplification of optical pulses, usually with ultrashort pulse durations in the picosecond or femtosecond domain. Multiple passes through the Gain medium are achieved by placing the gain medium in an optical resonator, together with an optical switch, usually realized with an electro-optic Modulator and a polarizer. As the number of round trips in the resonator can be controlled with the optical switch, it can be very large, SO that a very high overall amplification factor is achieved.