Autoalignment system for laser with unstable resonator

Abstract

A method and system for automatically aligning a high power laser. The high ower laser train includes an unstable resonator cavity and two turning mirrors to direct the pointing of the output laser beam. The autoalignment system is designed to perform two alignment tasks, the maintenance of output beam pointing stability and the establishment of resonator cavity mode control, by precisely adjusting the orientation of the end mirrors of the resonator cavity and the two turning mirrors. A HeNe laser, located at the output end of the high power laser train, propagates an alignment beam back along the laser train, parallel to the high power laser train. The alignment beam is divided into two separate alignment beams by means of a mirror splitter. One of the beams is directed on an optical alignment path which includes the two turning mirrors and is delimited by two null position detectors, one on an end mirror of the resonator cavity and one at the output end of the high power laser train. The other alignment beam is directed along the optical axis of the resonator cavity on an optical alignment path delimited by two more null position detectors, one on each of the two end mirrors of the resonator cavity. Since these two optical alignment paths include all the mirrors of the high power laser train, any misalignments in these mirrors will result in alignment beam deflections. The beam deflections are detected by the four null position detectors and translated, by means of an analog matrix control device, into corrective, correlative tilt adjustments to the mirrors of the high power laser train.