Coherent, Inc.

Joel Fontanella

Leon A Newman

Anthony J DeMaria

John T Kennedy

Robert Henschke

Richard A Hart

Lanny Laughman

Frederick W Hauer

David J Allie

W Shef Robotham, Jr

Vernon A Seguin

Eric R Mueller

Gongxue Hua

Christian J Shackleton

Adrian Papanide

Peter Rosenthal

Phillip J Gardner

David Schmelzer

Patrick T Tracy

Thomas V Hennessey, Jr

Raymond Michaud

David E Brown

David John Allie

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

An RF power-supply for driving a carbon dioxide COgas-discharge laser includes a plurality of power-oscillators phase-locked to a common reference oscillator. Outputs of the phase-locked power-oscillators are combined by a power combiner for delivery, via an impedance matching network, to discharge-electrodes of the laser. In one example the powers are analog power-oscillators. In another example, the power-oscillators are digital power-oscillators.

Multiple phase-locked loops for high-power RF-power combiners

A carbon-dioxide COgas-discharge laser is energized by the output a radio-frequency power supply (RFPS). Output-power of the laser is stabilized by adjustments of the RFPS responsive to periodic measurements of the laser output-power using detector output amplified by an amplifier. The amplifier has an offset-voltage which is subject to drift. A synchronous auto-zero arrangement is provided for canceling out the offset-voltage of the amplifier immediately prior to each periodic measurement of the laser output power.

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Electrical apparatus for connecting a radio frequency power-supply having two outputs to a load includes two radio frequency transmission-lines, each one connected to a corresponding power-supply output. A transformer arrangement connects the two transmission-lines to the load. Each transmission-line includes a series-connected pair of twelfth-wave transmission-line sections. The series-connection between the twelfth wave transmission-line sections in one transmission line is connected to the series-connection between the twelfth-wave transmission-line sections in the other by a device having an adjustable impedance.

A gas discharge laser including a lasing gas between discharge electrodes and has a power supply for generating RF pulses to be delivered to the electrodes of the laser for energizing the lasing gas. A sequence of RF simmer pulses is delivered to the electrodes. The simmer pulses create sufficient free electrons in the lasing gas to facilitate subsequent ignition of the discharge while not causing laser action. RF lasing pulses having a longer duration than the simmer pulses are delivered to the electrodes to ignite the discharge and provide corresponding laser output pulses. Delivery of the simmer pulses is suspended during delivery of the lasing pulses to avoid amplitude or pulse-width modulation of the laser output pulses by the simmer pulses.

Gas laser discharge pre-ionization using a simmer-discharge

An RF powered COgas-discharge laser includes discharge electrodes and a lasing gas mixture between the electrode. The lasing gas mixture is ionized when the RF power is applied to the electrodes and laser action is initiated when the RF power has been applied for a duration sufficient to ignite a discharge in the lasing gas mixture. The gas mixture is pre-ionized by periodically applying the RF power to the electrodes for a predetermined period during which ignition of a discharge is not expected to occur. RF power reflected back from the electrodes is monitored. If the monitored power falls below a predetermined level indicative of the imminent onset of laser action before the predetermined duration has elapsed, application of the RF power to the electrodes is terminated to prevent the laser action from occurring.

A gas discharge laser includes a laser housing including a laser gas and an electrode-assembly for lighting a discharge in the laser gas. The electrode assembly has a first resonant frequency when the discharge is not lit and a second resonant frequency when the discharge is lit. RF power delivering circuitry of the laser includes an arrangement for determining and recording the two resonant frequencies. RF power is applied to the electrodes at the first recorded resonant frequency to facilitate lighting of the discharge, and thereafter at the second resonant frequency to light and sustain the discharge.

Frequency-agile RF-power excitation for driving diffusion-cooled sealed-off, RF-excited gas lasers

A method of combining beams from a plurality of laser resonators includes frequency modulating the output of each of the lasers with one or more of the lasers frequency modulated out-of-phase with the others. The frequency modulated beams are directed along parallel spaced-apart paths and overlap in a plane along the paths to form a combined beam having a flat-topped intensity distribution.

Incoherent combination of laser beams

A RF shielded, series inductor, high power impedance matching network interconnector is provided for connecting an RF power supply to electrodes contained in the shielded, hermetically sealed laser tube housing of a slab laser system. The impedance matching interconnector comprises a short length of co-axial conductor and an impedance matching network that includes two L shaped networks. The inner conductor of the co-axial conductor is connected between the power supply output and the impedance matching network. The outer conductor of the co-axial conductor is grounded. The co-axial conductor has an impedance characteristic to match the power supply output impedance. The first L-shaped network includes a first inductor having a first end connected to the inner conductor of the co-axial conductor and a first capacitor connected to the second end of the first inductor and a second plate connected to ground. The second L shaped network includes a second inductor having a first end connected to the common connection between the second end of the first inductor and the first plate of the first capacitor and a second capacitor having a first plate connected to the second end of the second inductor and a second plate connected to ground. The common connection between the second end of the second inductor and the first plate of the second capacitor is connected through the shielded, hermetically sealed laser tube housing to the electrodes of the slab laser system. The two L-shaped networks may be implemented in a 'single capacitor' configuration for lower power applications or in a 'multi-capacitor' configuration for higher power applications.

The quality of pulses output from laser systems such as super-pulsed COslab lasers can be improved using half-wavelength electro-optic modulators (EOMs), in combination with thin film polarizers (TFPs). A voltage applied across a CdTe crystal of the EOM rotates the polarization of a pulse passing through the EOM by 90&#xb0;. The polarization determines whether the pulse passes through, or is redirected by, the TFP. The voltage applied to the crystal can be pulsed to prevent a drop in charge, which could allow radiation to leak to the application. A totem pole switch used to apply voltage to the EOM can receive a pulsed voltage for improved performance. Directing by the EOM allows pulses to be clipped at the front/back end(s), split into portions, and/or directed to separate scanners. Directing pulses or pulse portions to different scanners can increase the output of systems such as hole drilling systems.

A COlaser reference oscillator (RO) can provide injection seeding to a Q-switched (QS) or Q-switched cavity dumped (QSCD) COlaser, where the output frequency of the RO laser is locked to the peak of the laser line by the use of appropriate electronics to dither one of the resonator mirrors of the reference oscillator. This injected radiation seeds the radiation building up within the Q-switched laser cavity, such that the oscillating frequency favors the wavelength of the injected radiation. An electronic feedback control circuit can be used to lock an axial mode of the Q-switched laser to line center. The change in build-up time of the pulses within the QS laser can be used to maintain cavity length at a value that enables oscillating at the peak of the same laser line that is injected into QS laser.

This disclosure discusses techniques for obtaining wavelength selected simultaneously super pulsed Q-switched and cavity dumped laser pulses utilizing high optical damage threshold electro-optic modulators, maintaining a zero DC voltage bias on the CdTe electro-optic modulator (EOM) so as to minimize polarization variations depending on the location of the laser beam propagating through the CdSe EOM crystal, as well as the addition of one or more laser amplifiers in a compact package and the use of simultaneous gain switched, Q-switched and cavity dumped operation of COlasers for generating shorter pulses and higher peak power for the hole drilling, engraving and perforation applications.

Q-switched, cavity dumped laser systems for material processing

A laser includes a gain medium located in a laser resonator. The gain medium generates plane polarized radiation plane polarized in a first polarization orientation. An electro-optical switch is located in the resonator. When the switch is activated the polarization plane of the laser radiation is rotated to a second orientation after making a forward and a reverse pass through the optical switch. When the switch is deactivated, the polarization orientation of the forward and reverse transmitted laser radiation remains about the same. A polarization selective device is located in the resonator between the electro-optical switch and the gain medium. The polarization selective device is arranged to permit circulation in the resonator of laser radiation in the first polarization orientation, and to restrict circulation of laser radiation in the second polarization orientation. The Gain medium is energized and the switch activated to allow energy to build in the gain medium. The switch is then deactivated to allow laser radiation to circulate in the resonator and deliver a laser pulse. A method of activating the switch by a sequence of DC pulses is disclosed.

A simultaneously super pulsed Q-switched CO laser system for material processing is disclosed. The system comprises sealed-off folded waveguides with folded mirrors that are thin film coated to select the output wavelength of the laser. The system also comprises a plurality of reflective devices defining a cavity; a gain medium positioned within the cavity for generating a laser beam; a cavity loss modulator for modulating the laser beam, generating thereby one or more laser pulses; a pulsed signal generation system connected to the cavity loss modulator for delivering pulsed signals to the cavity loss modulator thereby controlling the state of optical loss within the cavity; a control unit connected to the pulsed signal generation system for controlling the pulsed signal generation system; and a pulse clipping circuit receptive of a portion of the laser beam and connected to the pulsed signal generation system for truncating a part of the laser pulses.

Q-switched CO2 laser for material processing

This disclosure discusses techniques for obtaining wavelength selected simultaneously super pulsed Q-switched and cavity dumped laser pulses utilizing high optical damage threshold electro-optic modulators, maintaining a zero DC voltage bias on the CdTe electro-optic modulator (EOM) so as to minimize polarization variations depending on the location of the laser beam propagating through the CdSe EOM crystal, as well as the addition of one or more laser amplifiers in a compact package and the use of simultaneous gain switched, Q-switched and cavity dumped operation of CO lasers for generating shorter pulses and higher peak power for the hole drilling, engraving and perforation applications.

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Tolland, CT, United States of America

Joel Fontanella