Spectra-physics Gmbh

Spectra Physics Lasers, Inc.

Bertram C Johnson

Richard L Herbst

John C DiFonzo

Glen R Blevins

James B Clark

Mark S Sobey

A non-linear frequency conversion device is tunable over a wide tuning range. An input source provides a first input beam with a frequency .lambda.1. A first frequency conversion crystal has an input beam face that is cut at a phase matching angle .theta.1 and is positioned on a first stage at a stage angle .alpha.1. The first frequency conversion crystal provides frequency conversion of the input beam of frequency .lambda.1 to a selected frequency .lambda.2 of a first portion of the selected tuning range. A second frequency conversion crystal has an input beam face that is cut at a phase matching angle .theta.2 and is positioned on a second stage at a stage angle .alpha.2. The second frequency conversion crystal provides frequency conversion of the input beam from a frequency .lambda.1 to a selected frequency .lambda.3 of a second portion of the selected tuning range. Only one of the frequency conversion crystals provides frequency conversion in the range for a particular input wavelength, while the other crystal is inactive, and serves as a beam displacement compensator. The non-linear frequency conversion device can be used for second harmonic generation, sum frequency mixing, difference frequency mixing, or optical parametric generation.

Multiple crystal non-linear frequency conversion apparatus

A high powered OPO system which produces a substantially collimated, low divergence output beam is based on the use of an unstable resonator. An optical parametric gain medium, such as beta-barium borate (.beta.-BBO), lithium tri-borate (LBO), cesium borate (CBO), potasium tri-phosphate (KTP), or other similar materials is mounted within the unstable resonator with suitable tuning mechanisms. Optics are provided for supplying a pump beam through the optical parametric gain medium to induce gain. In a preferred system, the unstable resonator comprises a positive branch, confocal unstable resonator. Further the unstable resonator may be injection seeded for a narrow linewidth output.

Optical parametric oscillator with unstable resonator

A pulsed laser system capable of operating at higher repetition rates, while maintaining the efficiency and beam quality of the output pulses comprises first and second gain media with one or more pump energy transducers, such as flashlamps, coupled with each of the gain media. A power supply generates a first sequence of pulses of input power and a second sequence of pulses of input power which drive respective subsets of the pump energy transducers in an independent timing relationship. Thus, two non-aligned 50 Hz sequences of input pulses which are interleaved generate an output pulse stream at 100 Hz from the laser system with the efficiency, beam quality, and average power comparable to that of a 50 Hz laser. By pumping subsets of the pump energy transducers coupled to a laser system in an interleaved fashion, higher repetition rates may be achieved with better output beam quality and higher average power than has been obtainable with prior art systems. The non-aligned timing also allows for variable pulse timing offsets.

High repetition rate pulsed laser

A Q-switch for a laser having a resonant cavity including an output coupler, a gain medium and a retro-reflecting mirror is mounted in the resonant cavity between the gain medium and the retro-reflecting mirror. The Q-switch comprises a polarizer and a phase retarding element (such as a Pockels cell) which includes a birefringent substrate for inducing a controllable phase retardation in the cavity mode in response to an applied electric field. A tiltable mount supports the phase retarding element so that the lasing axis lies essentially in a plane of the crystallographic axis 45.degree. from the direction of polarization, and lies at an adjustable angle relative to the crystallographic axis. A control circuit supplies an applied electric field within the substrate having a first magnitude in a first state and a second magnitude in a seocnd state. In the first state, the phase retarding element induces 90.degree. rotation in a round trip for the cavity mode. In the second state, the phase retarding element induces effectively no rotation (0.degree. or 180.degree.) for the cavity mode. Therefore, the resonant cavity achieves a high extinction ratio by proper adjustment of the adjustable angle.

Tunable electro-optic Q-switch, and lasers using same

A laser oscillator/amplifier system in which thermally induced birefringence in the gain media of the oscillator is compensated by thermally induced birefringence in the gain media of the amplifier. The system produces a quality output beam efficiently and with high power density in the preferred polarization. The oscillator cavity is characterized by a high reflector at one end and an output coupler at the second end with an oscillator gain medium exhibiting thermally induced birefringence in between. An amplifier exhibiting thermally induced birefringence which matches the thermally induced birefringence in the oscillator gain medium is mounted to receive the output of the oscillator cavity. A ninety degree rotator is mounted between the oscillator gain medium and the amplifier so that compensation for thermally induced birefringence in the oscillator gain medium is compensated by the matching thermally induced birefringence in the amplifier. The ninety degree rotator may be mounted inside the oscillator cavity, that is, between the oscillator gain medium and the output coupler; or it may be mounted outside of the oscillator cavity, that is, between the output coupler and the amplifier.

Laser oscillator/amplifier with compensation for stress birefringence

A laser beam shaper which provides polarized output with a high spatial quality, utilizing induced stress birefringence. The laser beam shaper in which light resonates along a resonant path defined by reflective surfaces includes a solid state medium, such as a Nd:YAG rod which exhibits thermally induced stress birefringence that is of known, azimuthally independent distribution in planes perpendicular to the resonant path. On either side of the medium, quarter-wave retardation plates are provided which create essentially circular polarization of the resonant light within the medium. Sandwiching the quarter-wave plates and the medium are the first and second polarizing elements, both of which are aligned along the same preferred plane. By inducing stress birefringence in the medium, an output beam is produced. A shape defined by the distribution of the birefringence is provided. With media such as YAG, the shape of the beam is round with high quality.

Apparatus using induced birefringence to improve laser beam quality

A laser amplifier with high gain and high power efficiency comprises a gain medium characterized by at least two optical paths through the gain medium. An optic supplies the input laser pulse along a first optical path, so that the laser pulse has a transverse dimension D.sub.i as it propagates along the first optical path and exits the gain medium as a first pass amplified pulse. A second optic expands the first pass amplified pulse in the transverse dimension to an expanded pulse with transverse dimension D.sub.e, and guides the expanded pulse along a second optical path through the gain medium. The laser pulse exits the gain medium as a second pass amplified pulse. A third optic in a preferred system guides the second pass amplified pulse along a third optical path through the gain medium so that the laser pulse exits the gain medium as the output pulse.

Multipass laser amplifier with at least one expanded pass

In a laser apparatus which includes a laser medium exhibiting thermally induced optical distortions, and flash lamp mounted near the laser medium to provide laser pumping radiation, an absorbing filter is mounted between the flash lamp and the laser medium for absorbing radiation in the output spectrum of the lamp which exhibits a low fluorescence efficiency in the laser medium. By absorbing radiation with the low fluorescence efficiency in the laser medium, heat which develops in the laser medium can be limited to control the thermally induced optical distortions.

Absorbing filter in pump cavity for control of beam quality

A tunable solid state laser oscillator with very narrow spectral line width for pulsed output comprises a solid state laser medium that generates a laser beam along a resonant path, a beam expander, such as a prism beam expander or cylindrical optic, and a grating mounted with an adjustable angle of incidence with respect to the laser beam. By adjusting the angle of incidence of the beam on the grating, the laser output wavelength is tuned. Further, the reflectivity of the grating provides very narrow spectral line width for oscillation in the laser over the entire tuning range.

Pulsed tunable solid state laser

A laser resonator generates a polarized output beam with a laser medium exhibiting thermally induced birefringence and a Y-shaped resonant cavity. A lasing axis extends between a first side and a second side of the laser medium, Radiation transmitted out of the first side of the laser medium has its polarization rotated by 90 degrees and is guided back along the lasing axis into the laser medium for a second pass. A polarizer is mounted on the second side of the laser medium for guiding the radiation having a first polarization along a first path and radiation having a second polarization that is 90 degrees from the first polarization along a second path. Both the first path and the second path include the lasing axis of the laser medium and form a Y-shaped resonant cavity. Along the first path, a high reflecting means is provided to reflect the radiation back along the first path. Along the second path, an output coupler is provided by which a component of the radiation is reflected back along the second path and a component is transmitted as the polarized output beam. A Q-switch is provided in the first path between the polarizer and the high reflecting means, or in the second path between the polarizer and the output coupler, or in both paths.

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Sunnyvale, CA, United States of America

Bertram C Johnson