Coherent, Inc.

Other

Bernard J Couillaud

Daniel K Negus

Luis A Spinelli

Gerald M Mitchell

Gilles A Feugnet

A birefringent filter ('BRF') unit, for use in the cavity of a tunable pulsed laser generating ultrashort pulses, including means for suppressing satellite pulses resulting from surface reflections. In one preferred embodiment, the inventive BRF has substantially parallel front and back surfaces, and is cut so that its optical axis is not parallel to its front surface. For example, the inventive BRF may be a quartz crystal having a thickness of 3 mm, with its optical axis oriented at an angle substantially equal to 50 degrees from the plane of its front surface. In a second preferred embodiment, the inventive BRF includes a relatively thick, non-birefringent component coupled with index matching material to a relatively thin birefringent component. In a third preferred embodiment, the inventive BRF includes a pair of thick birefringent components designed so that the ordinary ray of the first component becomes the extraordinary ray of the second component. In this third embodiment, the two components preferably have substantially equal birefringence N, and differ in thickness by an amount W chosen so that the overall optical phase shift induced by the inventive BRF is substantially equal to the optical phase shift induced by a conventional single-component BRF having thickness W and birefringence N.

Birefringent filter for use in a tunable pulsed laser cavity

Mode-locked pulsed output is induced in a laser by introducing a varying frequency dependent loss in the cavity. The varying, frequency dependent loss allows a large number of longitudinal modes to oscillate. In one of the preferred embodiments of the subject invention, the varying frequency dependent loss is generated by reciprocating one of the mirrors of the resonator. In this embodiment, the laser has a resonator with a primary light path defined by first and second end mirrors. A gain medium is located between the end mirrors. A beam splitter is provided for redirecting the light into a secondary light path. A third mirror functions to feed back the light into the primary light path. Pulse formation is induced by varying the path length of one of the two paths by reciprocating an end mirror. Moving the mirror creates varying interference effects when the light energy is recombined at the beam splitter. The mirror is reciprocated relatively slowly, yet ultra-short pulses are generated.

Mode-locked laser

The subject invention relates to method of suppressing one of the counterpropagating intracavity pulses generated in a dye laser synchronously pumped by the output of a mode locked Q-switched pump laser. The method includes extracting a portion of one of the pulses generated in the cavity such that the other pulse experiences a greater effective gain. The pulse with the highest effective gain will dominate the other pulse and at the steady state only one pulse will exist in the cavity. In the preferred embodiment, a double pass acousto-optic cell is used to extract the both the unwanted pulse and, at a later time, the high energy, useful pulse. In this case, maximum efficiency is achieved by placing the dye cell at one of a number of well defined locations within the optical cavity.

Growing community of inventors

Palo Alto, CA, United States of America

Bernard J Couillaud