Abstract: A probe station which comprises a base machine, a chuck mounted on the base machine to hold a device under test (DUT), a probe platen mounted on the base machine on which to mount probes for the device, a microscope mounted on the base machine having a field of view on the DUT on the chuck, and a single laser, mounted with the microscope. The single laser supplies an output beam in a plurality of wavelengths through the microscope optics on a beam line to the field of view of the microscope. The laser system includes a solid state laser, a harmonic generator coupled with the solid state laser, and switchable optics for selecting the wavelength of the output beam from among two or more selectable wavelengths. In addition, the laser system includes a variable attenuator, based on a unique half-wave plate, which operates for the plurality of wavelengths which are selectable as outputs in the infrared (1064 nanometers), in the green (532 nanometers), and in the ultraviolet (355 nanometers, or 266 nanometers).

Abstract: A multi-layer graded reflectivity mirror (GRM) with high effective reflectivity is suitable for use in large aperture laser systems with relatively low gain. The GRMs are manufactured with multiple dielectric layers with a thickness profile that eliminates the interference fringes, while providing a reflectivity which tapers smoothly from a peak to zero. The mirror is formed on a substrate having a first surface and a second surface opposite the first. The substrate consists of a material which has low absorption at a given wavelength .lambda.. A first dielectric layer is formed on the first surface of the substrate which has an index of refraction n.sub.1 and having an optical thickness profile with a maximum optical thickness of .lambda./4 at a center which essentially continuously decreases away from the center to a minimum optical thickness of Z at a perimeter P. A second dielectric layer is formed on the first dielectric layer having an index of refraction n.sub.

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 tunable solid state laser having a titanium:sapphire grain medium and a birefringent filter mounted within a resonant cavity is provided. The resonant cavity is longitudinally pumped. The cavity is enclosed in a casing which has a small window admitting the pump beam into the resonant cavity, and a small window with an anti-reflection coating allowing the laser output to exit the casing. The casing is maintained at a positive pressure of nitrogen gas during operation of the laser to purge the resonant cavity of air and water vapor.

Abstract: A prism beam expander in which the incoming beam is essentially achromatically expanded by 100-500 times in one dimension with transmission through the prism beam expander exceeding 40%. In addition, the input beam is nearly collinear with the output beam. The prism beam expander includes 6 prisms in a preferred system, at least 2 of the apexes of which are oriented on the first side of the optical path while at least 2 of the apexes of the remaining prisms are oriented on the second side of the optical path. The achromatic, high-magnification collinear prism beam expander is used in a tunable laser achieving very narrow linewidths.

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 KTP crystal in a nonlinear optical device is heated to and operated at a temperature of at least 50.degree. C. and less than 350.degree. C., and more preferably about 90.degree. C. to about 200.degree. C., and most preferably to about 100.degree. C. to about 125.degree. C., to reduce drift and damage. The KTP crystal is placed in an oven or other heating device, which may be regulated or unregulated. The KTP may be cut at the room temperature phase matching angle and angle tuned for operation at the higher temperature, or the KTP may be cut at the correct angle for phase matching at the operating temperature.

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: In a high power laser, such as one employing a relatively high gain lasing medium such as CO.sub.2 or Nd:YAG, the optical resonator for the laser comprises a positive branch unstable resonator. The output beam is coupled from the unstable resonator by means of a partially transmissive mirror of the resonator, whereby a filled-in beam is obtained while facilitating optical alignment of the output coupling means. In a preferred embodiment, the optical resonator comprises a pair of mirrors collinearly arranged on the optical axis of the resonator to supply an output beam which is collinear with the optical axis of the resonator. The filled-in output beam is of generally uniform power density across the transverse cross sectional dimensions thereof, whereby a near diffraction limited output beam is obtained with more uniform power density.

Abstract: The high power laser includes a high gain medium (>80%) such as a lightly doped Nd:YAG rod contained within an unstable optical resonator of the type wherein power flows outward from the optical axis of the resonator. The output beam is coupled out of the resonator by means of a coupling device having a high coupling factor (>55% of the circulating power inside the optical resonator) and in a preferred embodiment the coupling factor is as high as 80-90%. The optical resonator is preferably a confocal resonator employing one concave mirror and one convex mirror. The convex mirror forms the output coupling device for providing a high degree of diffraction output coupling around the periphery of the output mirror. The output beam is collimated in the region of the output mirror.

Abstract: In a transversely pumped dye laser, such as a laser oscillator or laser amplifier, the optical pumping radiation is directed into the dye laser gain medium with the angle of divergence of the Poynting vector of the pumping wave radiation being not less than 45.degree. and preferably 90.degree. from the Poynting vector, or its reciprocal, of the optical wave radiation being amplified within the dye laser gain medium, whereby transverse pumping is obtained. In addition, the optical pumping wave radiation is directed into the dye laser gain medium with the angular divergence of the polarization of the electric vector of the pumping wave radiation being not greater than 45.degree., and preferably parallel to the polarization of the electric vector, or the reciprocal thereof, of the optical wave radiation which is being amplified by the dye laser gain medium, whereby the efficiency of conversion of pump energy into amplified optical wave energy is enhanced.

Abstract: A tunable source of infrared radiation is obtained by irradiating an assemblage of Raman active gaseous atoms or molecules with a high intensity pumping beam of coherent radiation at a pump frequency .omega..sub.p to stimulate the generation of Stokes wave energy at a Stokes frequency .omega..sub.s and to stimulate the Raman resonant mode at the Raman mode frequency .omega..sub.R within the irradiated assemblage where the pump frequency .omega..sub.p minus the Stokes frequency .omega..sub.s is equal to the Raman mode frequency .omega..sub.R. The stimulated assemblage is irradiated with a tunable source of coherent radiation at a frequency .omega..sub.i to generate the output infrared radiation of the frequency .omega..sub.0 which is related to the Raman mode frequency .omega..sub.R and the input wave .omega..sub.i by the relation .omega..sub.0 =.omega..sub.i .+-..omega..sub.R. In one embodiment the interaction between the pump wave energy .omega..sub.p and the tunable input wave energy .omega..sub.

Abstract: Output coherent infrared radiation is obtained in a continuously tunable band from 1.4 microns to 25 microns and longer wavelengths. The 1.06 micron output of a Nd:YAG laser, or a harmonic thereof, is difference mixed in a nonlinear crystal, as of LiIO.sub.3 or LiNbO.sub.3 with a synchronously pumped output of a tunable dye laser oscillator to produce a first tunable output over the range of 0.7 micron to 5.0 microns. The output of the crystal mixer is amplified or difference mixed in a second nonlinear crystal mixer with the 1.06 pump output to produce an output tunable over the range of 1.4 microns to 25 microns and longer wavelengths. Suitable second crystal mixers comprise LiNbO.sub.3 for the range of 1.4 to 4.4 microns and operable as an amplifier in the range of 1.4 microns to 2.1 microns, and as a difference mixer in the range of 2.1 to 4.4 microns, AgGaS.sub.

Abstract: A high power single mode laser is disclosed which includes a Q-switch for switching the laser on in two stages: firstly, to a relatively high loss level just above threshold where it is held to permit a train of relaxation oscillator spikes to be established and then it is switched to a second stage in which the Q-switch is in a lossless state to allow the resonant mode within the laser to build up to maximum power. An optical detector monitors the resonant optical radiation level within the optical resonator and produces an output signal for each of the relaxation spikes. A trigger circuit, responsive to the detected oscillator spikes, triggers the Q-switch so as to switch it to the second or lossless state upon receipt of the second or any other subsequent relaxation oscillator spike, whereby single longitudinal mode operation of the laser is enhanced.

Abstract: A meniscus lens is disclosed for use in high power light beam applications, such as in the optics of a high power laser where the laser beam intensity is in excess of one megawatt per square centimeter. The meniscus lens is designed such that light rays reflected from the lens are divergent so that no back focal points are created by the lens. In this manner, undesired dielectric breakdowns and damage to optical components and the like are avoided due to reflected back focal points. In one embodiment of the present invention, the output mirror of a high power laser is deposited upon the convex face of a meniscus lens, such lens being designed to avoid back focal points, whereby the construction of the output mirror is greatly simplified.