Abstract: A cascaded harmonic generator, for cascaded optical harmonic generation from an optical beam provided by a laser source, may include a second harmonic generator to generate a second harmonic optical beam based on a residual beam associated with the optical beam. The cascaded harmonic generator may include a third harmonic generator to generate a third harmonic optical beam based on the second harmonic optical beam and the optical beam. The third harmonic generator may be positioned in an optical path upstream from the second harmonic generator. A harmonic generator delay time, associated with the optical path, may be approximately equal to, or may be an approximate integer multiple of, a laser source round-trip time.

Abstract: A cascaded harmonic generator, for cascaded optical harmonic generation from an optical beam provided by a laser source, may include a second harmonic generator to generate a second harmonic optical beam based on a residual beam associated with the optical beam. The cascaded harmonic generator may include a third harmonic generator to generate a third harmonic optical beam based on the second harmonic optical beam and the optical beam. The third harmonic generator may be positioned in an optical path upstream from the second harmonic generator. A harmonic generator delay time, associated with the optical path, may be approximately equal to, or may be an approximate integer multiple of, a laser source round-trip time.

Abstract: A cascaded harmonic generator, for cascaded optical harmonic generation from an optical beam provided by a laser source, may include a second harmonic generator to generate a second harmonic optical beam based on a residual beam associated with the optical beam. The cascaded harmonic generator may include a third harmonic generator to generate a third harmonic optical beam based on the second harmonic optical beam and the optical beam. The third harmonic generator may be positioned in an optical path upstream from the second harmonic generator. A harmonic generator delay time, associated with the optical path, may be approximately equal to, or may be an approximate integer multiple of, a laser source round-trip time.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A Q-switched/mode-locked Nd:YAG laser oscillator employing simultaneous active (electro-optic) and passive (saturable absorber) loss modulation within the optical cavity is described. This "dual modulation" oscillator can produce transform-limited pulses of duration ranging from about 30 psec to about 5 nsec with greatly improved stability compared to other mode-locked systems. The pulses produced by this system lack intrapulse frequency or amplitude modulation, and hence are idealy suited for amplification to high energies and for other applications where well-defined pulses are required. Also, the pulses of this system have excellent interpulse characteristics, wherein the optical noise between the individual pulses of the pulse train has a power level well below the power of the peak pulse of the train.