Coherent, Inc.

Gregory Dumond

Robert J Rorden

David A Dewey

David Trost

Jerzy Orkiszewski

Michael Arnett

Ralph Saunders

A laser master-oscillator power-amplifier (MOPA) is operated to provide successive bursts of ultrashort pulses. The pulse-bursts are selected by an optical modulator from a pulse train delivered by the master oscillator prior to amplification in the power amplifier. The optical modulator has a selectively variable transmission specified by an analog voltage signal having a stepped waveform. The voltage signal is delivered by a sequentially-switched parallel switch-array connected in parallel with a parallel DAC having multiple parallel DC voltage outputs corresponding to steps of the stepped waveform.

Laser-MOPA with burst-mode control

Typically, a laser emits significant energy after a control signal is generated to disable the power supply. The inherent delay between generation of a control signal for shutting off a laser power supply and actual termination of an output beam pulse in response to the control signal, is compensated in the context that the control signal is generated automatically upon coincidence of measured output beam power with a preset threshold value. Power supplied to a laser is modulated to cause generation of a pulsed laser output beam. The cumulative energy of each output beam pulse is monitored and a feedback signal indicative of measured output beam pulse energy is supplied to the power supply. The feedback signal is compared with a user-selected threshold value, and a control signal is generated for terminating the output beam pulse (by terminating input power to the laser) when the measured output pulse energy reaches the threshold value. By generating the threshold signal to have a value representing a threshold output beam pulse energy that is lower than a desired output beam pulse energy, the threshold signal is generated in a manner which compensates for the inherent delay between generation of the control signal and the actual termination of the output beam pulse in response to the control signal. This prevents delivery of significant output beam energy in excess of a user-selected amount.

Electronically pulsed laser system

A laser power supply including circuitry for converting standard, 115-120 volt, AC power from a wall outlet to current pulses for powering a laser, to generate a pulsed laser output beam having laser pulse amplitude and duration matching pre-selected parameters. In a preferred embodiment, the invention powers an argon laser tube and generates output laser beam pulses having power in the range from about 50 milliwatts to 2 watts, and duration in the range from about 0.01 second to 2 seconds. The invention converts standard AC power to current pulses having controlled duration, average amplitude, and ripple amplitude for powering a laser, and can produce laser output beam pulses with a turn-on time of less than 1 millisecond, with a switching frequency in the range from about 10 to 20 KHz without significant overshoot. A preferred embodiment of the invention powers a gas laser tube, and includes a magnet control circuit which enables the laser tube magnet in the absence of a special magnet control signal received at the magnet control circuit from a fiber optic link. The invention is particularly suitable for powering gas laser systems for use in ophthalmic and surgical applications, but is also useful for powering other types of laser systems. An important advantage of the invention is that its ability to accept standard, AC power from a wall outlet enables the inventive apparatus to be moved conveniently between treatment rooms (for use in any of the rooms), without the expense and inconvenience of installing special wiring.

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Santa Clara, CA, United States of America

Gregory Dumond