Spectra Physics Lasers, Inc.

Harold D DuBose

Kevin K Holsinger

Michael McNeal

A servo controlled laser system is provided which provides a laser output beam having reduced optical noise. The laser system may be any type of laser system and preferably is an ion laser system. The servo controlled laser system includes a laser head providing a laser output beam and a power driver coupled to the laser head which supplies input power to the laser head. The laser system also includes a light detector in the path of the output beam which generates an alternating current signal in response to the amount of optical noise detected in the laser output beam. A signal amplifier is coupled to the light detector for receiving and amplifying the alternating current signal. A wire couples the signal amplifier to power driver compensator circuitry which receives the amplified alternating current signal from the wire and, in response, adjusts the input power to reduce optical noise. In instances where a length of the wire is positioned sufficiently near an electrically noisy environment such that the electrically noisy environment modifies the amplified alternating current signal, the significance of the modification to the amplified alternating current signal is reduced by amplifying the alternating current signal prior to exposing the alternating current signal to the electrically noisy environment, thereby enabling a significant reduction in the optical noise present in the laser output beam. A method for producing a laser output beam having reduced optical noise is also provided using the servo controlled laser system.

Optical noise reduction circuitry for laser systems

A controller including a closed loop servo system for a laser, or other entity is capable of substantial reductions in predictable, periodic noise such as the line noise induced by the source of alternating current electrical power, and in random noise as well. The servo circuit includes resources which develop a stored version of the predictable noise and uses the stored version of the predictable noise to compensate for the predictable noise. According to another aspect, the servo circuit includes resources which automatically adjust loop gain as gain in the entity being controlled and the loop as a whole system varies. The resources which generate the stored version of the predictable noise may be operated in either analog or digital formats. The sampling resources include, in an analog/digital embodiment, a plurality of charge holding devices, Multiplexing circuitry is coupled to the charge holding devices, and connects a selected charge holding device to a sample node which receives the feedback signal. Control circuits control the multiplexing circuitry to switch, in sequence, the plurality of charge holding devices to the sampling node in synchronism with the predictable periodic noise so that a stored version is developed in the plurality of charge storage devices. In addition, the servo circuit includes resources which automatically adjust loop gain as the slope of the laser system varies, which substantially reduces both random and periodic noise.

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Mountain View, CA, United States of America

Harold D DuBose