Massachusetts Institute of Technology

Jyhpyng Wang

James G Fujimoto

James Gregory Goodberlet

Peter A Schulz

This invention relates to a tunable solid-state laser which generates ultrashort output pulses with continuous wave pumping. The device includes a lasing medium having a gain cross section of 10.sup.-18 cm.sup.2 or less and mode beating characteristics, which lasing medium is mounted in a laser cavity. A continuous wave pumping beam is applied to the lasing medium causing an output, a portion of which is applied to an intensity dependent nonlinear cavity. The output applied to the nonlinear cavity is retroreflected back through the cavity and is interferometrically combined with the laser output. The relative lengths of the cavities are initially selected such that phase changes caused by the nonlinear medium result in substantially maximum enhancement of intensity peaks of the laser output, causing self starting of pulsed operation. Once pulsed operation is achieved, the cavity lengths may be adjusted to optimize interferometric addition of peak outputs and interferometric cancellation of pulse wings, resulting in a laser output formed of ultrashort pulses. For preferred embodiments, the laser is a titanium sapphire laser, and the nonlinear cavity contains a single mode optical fiber which induces intensity dependent phase changes in an optical signal passing therethrough. A feedback circuit is preferably provided to stabilize pulse operation.

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Cambridge, MA, United States of America

Jyhpyng Wang