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: In a high power laser the optical resonator elements, such as reflectors for the optical resonator and optical pump are supported in optical alignment from a structural beam of generally L-shaped cross section and made of high thermal conductivity material such as copper or aluminum via the intermediary of a plurality of longitudinally directed rods made of a low thermal expansion material such as quartz or Invar. The rods are supported at one end from the L-shaped beam via leaf springs and they are rigidly coupled to the L-shaped beam at their other ends. The remaining elements such as the optical pump, Q switch and polarizers are supported directly from the L-shaped structural beam.

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: In an optically pumped high power laser the optical pump includes a housing containing a pair of flash lamps and an elliptical reflector assembly for reflecting the optical pumping radiation into the laser gain medium, such as a YAG rod. Water coolant is directed through the housing in contacting relation with the YAG rod and flash lamps. An ultraviolet band reject filter, comprising a split cylindrical sleeve, is disposed surrounding the laser gain medium in between the laser gain medium and the flash lamps and in contact with the water coolant.

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.