Coherent, Inc.

Klaus Hachfeld

James L Hobart

Joseph W Kantorski

A rod laser having a ring cavity configuration, and including a polarization rotator to compensate for birefringence of the laser's rod. Preferably, the rotator is a 90.degree. crystal quartz rotator. In a preferred embodiment, the ring laser is a stable quasi-unidirectional, non-confocal solid state ring laser. A telescope, including at least two lenses with variable inter-lens spacing, is preferably positioned in the laser beam path as closely as possible to the laser rod. The spacing between the telescope lenses is preferably controlled by a servo mechanism. In a preferred embodiment, a power density detector is provided for producing a beam power signal, and a means (which may include a microprocessor) coupled to the power density detector generates a servo mechanism feedback control signal from the beam power signal. Since the system of the invention maintains a high quality output beam having low far-field beam divergence and small laser beam focal spot diameter, over a wide and varying range of output beam power, the output beam is particularly useful for such applications as high speed drilling, welding, and cutting.

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Sturbridge, MA, United States of America

Klaus Hachfeld