System for generating coherent single-frequency single transverse mode light pulses

A system is provided to generate coherent single-frequency and single transverse mode light pulses. A laser produces a linearly-polarized continuous wave beam defined by a single longitudinal and transverse mode. A first rotator processes the beam such that optical polarization is rotated during a first time period and not rotated during a second and third time period. A second rotator is operated during the first period to rotate optical polarization of the beam, during the second period to not rotate the beam, and during the third period to rotate the beam. An optical loop amplifies the beam during the first and second periods. An amplifier device can be added to the loop for amplification. A first beam splitter allows the beam to enter the loop and a second splitter directs the beam along the loop during the first and second periods and out of the loop during the third period.