Coherent, Inc.

Other

Vernon A Seguin

Leon A Newman

Lanny Laughman

Anthony J DeMaria

Christian J Shackleton

John T Kennedy

Peter P Chenausky

Eric R Mueller

Adrian Papanide

Joel Fontanella

Phillip J Gardner

R Russel Austin

Luis A Spinelli

Hisashi Matsumoto

Richard S Harris

Frederick W Hauer

Peter Rosenthal

David Schmelzer

Robert Henschke

Corey M Dunsky

Thomas V Hennessey, Jr

Raymond Michaud

Joseph S Smucz

Thomas J Hennessey, Jr

Christian Shackleton

A Q-switched gas laser apparatus with bivariate pulse equalization includes a gas laser, a sensor, and an electronic circuit. A Q-switch that switches the laser resonator between high-loss and low-loss states to generate a pulsed laser beam. The sensor obtains a measurement of the pulsed laser beam indicative of the laser pulse energy. The electronic circuitry operates the Q-switch to (a) repeatedly switch the laser resonator between the high-loss and low-loss states to set a repetition rate of laser pulses of the pulsed laser beam, (b) adjust a loss level of the low-loss state, based on the pulse energy measurement, to achieve a target laser pulse energy, and (c) adjust a duration of the low-loss state to achieve a target laser pulse duration. By adjusting both pulse energy and duration, uniform pulse energy and, if desired, uniform pulse duration are achieved over a wide range of repetition rates.

Pulse equalization in Q-switched gas lasers

A carbon dioxide gas-discharge slab-laser is assembled in a laser-housing. The laser-housing is formed from a hollow extrusion. An interior surface of the extrusion provides a ground electrode of the laser. Another live electrode is located within the extrusion, electrically insulated from and parallel to the ground electrode, forming a discharge-gap of the slab-laser. The electrodes are spaced apart by parallel ceramic strips. Neither the extrusion, nor the live electrode, include fluid coolant channels. The laser-housing is cooled by fluid-cooled plates attached to the outside thereof.

Conductively-cooled slab laser

A carbon dioxide gas-discharge slab-laser is assembled in a laser-housing. The laser-housing is formed from a hollow extrusion. An interior surface of the extrusion provides a ground electrode of the laser. Another live electrode is located within the extrusion, electrically insulated from and parallel to the ground electrode, forming a discharge-gap of the slab-laser. The electrodes are spaced apart by parallel ceramic strips. Neither the extrusion, nor the live electrode, include any direct fluid-cooling means. The laser-housing is cooled by fluid-cooled plates attached to the outside thereof.

A carbon-dioxide (CO) gas-discharge slab laser includes elongated discharge-electrodes in a sealed enclosure. Radio Frequency (RF) power is supplied to the electrodes via an impedance matching network and a co-axial electrical low inductance transmission line feed-through sealed to the enclosure. The feed-trough includes two spring contacts which are configured to be spring compression push-fit in grooves in edges of the discharge-electrodes. A central conductor of the feed-through is fluid cooled. A capacitor of the impedance matching network is assembled on the central conductor as an integral part of the feed-trough.

Hermetically-sealed RF feed-through with integrated capacitor

A pulsed COlaser is Q-switched by an intracavity acousto-optic (AO) Q-switch including an AO material transparent at a fundamental wavelength of the laser. In one example the AO material is germanium.

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A laser mirror assembly is disclosed with improved pointing stability. An elongated mirror includes a concave reflecting portion. A pair of elongated planar portions extend parallel to the concave reflecting portion on either side thereof. The planar portions are stepped down from the reflecting portion. The mirror is formed from copper. A pair of stainless steel strips are connected to planar portions. The bimetallic effect between the copper mirror and the stainless steel strips operates to counteract the warping of the mirror due to differential heating effects which arise during operation. In an alternate embodiment, a pair of aluminum strips are mounted on the rear surface of the mirror.

Thermal distortion compensation for laser mirrors

Through the use of a relatively inexpensive third mirror on a novel folded hybrid unstable resonator configuration, the optimum output coupling for a given laser design can be explored quickly and easily with a minimum of intracavity mirror alignment. No changes in either the radii of curvature of the three cavity optics or their spacing are required for this exploration. In addition to providing techniques for purposefully and systematically introducing mirror edge effects or avoiding edges effects altogether, the invention provides that output beams of different width can be advantageously explored in a relatively simple and straightforward manner. The invention provides that higher geometric magnification cavity designs may be made compatible with low diffraction output coupling in a configuration that uses only three totally reflecting optics.

Unstable resonator with variable output coupling

A low inductance, hermetically sealed, RF shielded feed-through is provided for exciting low impedance discharges associated with high power COslab lasers. The feed-through mechanically obtains RF contact, preferably, at the center of the length of the electrodes that are inserted within the long laser housing, thereby making it easier to obtain a uniform electric field distribution along the length of the electrodes.

High power low inductance RF hermetic sealed feed-through for slab CO2 lasers

An improved laser system includes a sealed-off, RF excited, diffusion cooled, high pressure, short pulsed, high peak power waveguide and slab COlaser that avoids problems typically associated with obtaining a diffused discharge at high gas pressures, without arcing and without corona, while maintaining the unsaturated gain and gas temperature experienced at low pressures and scaling to higher pressures. Such a system has a long operating life-time, and is capable of operation at high gas pressures to obtain relative fast rise and fall time pulses. The system emits relatively short pulse widths, with pulse energies up to and exceeding 30 mJ, with reasonably high pulse repetition rates. The system also has a low pulsed RF power duty cycle, thereby enabling the generation of high peak power pulses, as well as reasonable average power and reasonably high peak powers.

A COlaser has a resonator mirror that oscillates about an axis perpendicular to the resonator axis through an angular range of oscillation sufficient that the resonator is only able to deliver radiation for a fraction of an oscillation period of the mirror. In one example of the laser, the oscillating mirror is an end-mirror of the resonator. In another example, the oscillating mirror is a fold mirror of the resonator.

Various electro-optical modulator module designs are presented, which can provide for uniform, symmetric, and efficient heat removal for mode-locking, Q-switching, and/or cavity dumping operations. Heat can be uniformly extracted from an EO crystal without imposing undue stress, thereby preventing birefringence and laser beam degradation. A liquid-cooling approach can be used for high-duty operations, such as mode-locking operations. Efficient heat removal can prevent thermal run-away from electrical heating of the crystal due to the large drop in the electrical resistance of CdTe with increasing temperature when operated above 50&#xb0; C. RF or video arcing and subsequent damage to the EO crystal can be prevented by surrounding the crystal with a low dielectric constant material that lowers the capacitance coupling to ground, while still maintaining good thermal cooling.

A slab laser includes two elongated electrodes arranged spaced apart and face-to-face. Either one or two slabs of a solid dielectric material extend along the length of the electrodes between the electrodes. A discharge gap is formed either between one of the electrodes and one dielectric slab, or between two dielectric slabs. The discharge gap is filled with lasing gas. A pair of mirrors is configured and arranged to define a laser resonator extending through the gap. An RF potential is applied across the electrodes creating a gas discharge in the gap, and causing laser radiation to circulate in the resonator. Inserting dielectric material between the electrodes increases the resistance-capacitance (RC) time constant of the discharge structure compared with the RC time constant in the absence of dielectric material. This hinders the formation of arcs in the discharge, which enables the laser to operate with higher excitation power, higher lasing gas pressure, and higher output power than would be possible without the dielectric inserts.

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Windsor, CT, United States of America

Vernon A Seguin