Abstract: A non-linear optical device in which quasi-phase matching between different optical waves of differing polarizations and refractive indices increases the interaction length between the waves. The quasi-phase matching structure includes a periodic structure over which the non-linear coefficient varies with a given period, preferably the sign of the non-linear coefficient being inverted between two alternating regions. In LiNbO.sub.3, the periodic structure can be achieved by electrical poling. The required period length is increased by selecting light waves of different polarizations for the non-linear interaction such that a large portion of the dispersion between the waves of different wavelength is compensated by the birefringence of the waves of different polarization. In particular, periodic poling can quasi-phase match radiation in the range of 0.80 .mu.m to 1.2 .mu.m to generate second harmonic generation radiation in the blue and green visible spectrum.

Abstract: A laser system in which an intense laser beam of a predefined pumping wavelength traverses a non-linear material, such as crystalline lithium niobate, that has been impressed with one or more quasi phase matching (QPM) gratings is disclosed. Quasi phase matching compensates for the dispersion or birefringence in a non-linear material by modulating the non-linearity with the proper period such that the different wavelengths involved in the non-linear process stay in phase over a long interaction length. The first QPM grating promotes the parametric generation of a resonant signal whose wavelength is determined by the grating period. According to the invention, either a second QPM grating impressed in the same medium or a different order of the first QPM grating promotes the non-linear interaction between the resonant signal and another optical signal traversing the non-linear material.

Abstract: A laser system in which an intense laser beam of a predefined pumping wavelength traverses a non-linear material, such as crystalline lithium niobate, that has been impressed with one or more quasi phase matching (QPM) gratings is disclosed. Quasi phase matching compensates for the dispersion or birefringence in a non-linear material by modulating the non-linearity with the proper period such that the different wavelengths involved in the non-linear process stay in phase over a long interaction length. The first QPM grating promotes the parametric generation of a resonant signal whose wavelength is determined by the grating period. According to the invention, either a second QPM grating impressed in the same medium or a different order of the first QPM grating promotes the non-linear interaction between the resonant signal and another optical signal traversing the non-linear material.

Abstract: Apparatus for providing a laser light beam or an amplifier light beam that is scalable to very high light beam output power by use of approximately identical optical sections, each section containing one or more laser gain media and one or more fold mirrors, spaced apart from the laser gain media by a distance d. The laser gain media or the fold mirrors, or both, have a curved reflecting surface of radius R. The lengths d and R are chosen to provide a stable optical system within each optical section and to compensate for the development of a thermal lens within each laser gain medium when this medium is pumped by a light source. The optical sections may be concatenated to scale the light beam output power upward without limitation, except for optical absorption and losses that occur at each reflecting surface.

Abstract: A miniature laser cavity in which a solid-state lasing gain element and a Q-switch have respective end surfaces at substantially the Brewster angle, parallel to and facing each other, and separated by a narrow gap occupied by a transparent low-index-of-refraction material.

Abstract: A diode pumped solid-state laser is disclosed having: a block of a lasing gain material with at least two optical surfaces and a cavity means positioned around the block to define a laser cavity which includes a mode shaping means to form an eliptical resonator mode between the optical faces within the block; a high aspect ratio pumping laser diode light source is positioned outside one of said optical faces; and a means to image the pumping light beam from said source to substantially match the elliptical resonator mode.

Abstract: A diode imaging system using a single objective lens and a single cylindrical lens. This imaging system does not image perfectly point-to-point, and although not an apparent extension of imaging systems known in the prior art, it works advantageously for imaging beams from diode lasers having long narrow junctions used in pumping solid-state lasers.

Abstract: An optical Faraday isolator includes a slab of Faraday rotator medium coated to define input and output faces and internal reflective surfaces for causing the beam to travel between the input and output faces along a zig-zag path. Permanent magnets polarized in a direction normal to the plane defined by the zig-zag beam path are disposed on opposite sides of the beam path. The magnets are paired on each side with serially alternating polarity and the like poles are in transverse registration on opposite sides of the beam path to produce an intense, unidirectional magnetic field parallel to the beam path within the rotator slab. A quarterwave plate introduces a compensating amount of elliptical polarization to cancel unwanted elliptical polarization effects of the slab and its coatings. A beam shaving aperture at the exit of the slab shaves off divergent backward travelling rays.

Abstract: A laser photometer including means forming an unsupported curtain of liquid sample, means for focusing a laser beam at a sample volume in the unsupported liquid curtain, means for receiving a cone of light issuing from the sample in an incremental angle .DELTA..theta. at an angle .theta., means for focusing the cone of light at a field stop and a detector for receiving the power passing through the aperture.BACKGROUND OF THE INVENTION1. Field of the InventionThis invention relates to laser light scattering photometers used to measure the size of particles dispersed in liquids and, more particularly, to a particle handling technique wherein the particles are contained in a thin flat unsupported curtain of the liquid which contains the scattering volume.2. Description of the Prior ArtWhen a beam of radiant energy (light) is incident upon a particle, a portion of this energy will be scattered.

Abstract: An optical cavity for a flash lamp pumped dye laser including a pumping cavity, a birefringent filter and a plurality of frequency doubling crystals. Within the pumping cavity the flash lamp is cooled by forced air convection and operated with a D.C. simmer current. Simultaneously, the dye carrying conduit within the pumping cavity is cooled with water. The operating life of the dye is increased by using selectable filters to remove the ultraviolet radiation eminating from the flash lamp before it falls on the dye. The construction of the pumping cavity permits changing the flash lamp and the dye conduit without disturbing the optical path of the laser.