Abstract: A third-harmonic crystal has a Brewster-cut dispersive output surface for separating the p-polarized fundamental and third-harmonic beams without introducing losses into the beams. The output surface of the third-harmonic crystal is optically uncoated, and thus insensitive to potential ultraviolet (UV)-induced damage. Frequency doubling and tripling lithium triborate (LBO) crystals are used with a Brewster-cut Nd-YAG active medium in a resonant cavity to generate UV light at 355 nm from infrared (IR) light at 1064 nm. Except for the tripling crystal output surface, the doubling and tripling crystal optical surfaces are normal-cut and anti-reflection (AR) coated.

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 solid-state laser in which a rod (10) of lasing material is held within an optical cavity formed within a cooling block (40) having a highly surface facing the rod. A longitudinal slit (44) formed in the block from the optical cavity to the outside allows the pumping light from an emission line (36) of semiconductor stripe lasers (30) fabricated on a laser bar (28) to irradiate the laser rod and multiply reflect within the optical cavity. Thereby, pump light is efficiently absorbed by the laser rod, and the laser rod is thermally controlled. Alternatively, cooling liquid (124) can flow axially along the laser rod and within an axially extending optical cavity formed by a reflective coating (125) deposited on a tube (122) enclosing the cooling liquid and having a slit (126) through which pump light is irradiated.

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 multiple-pass laser amplifier that uses optical focusing between subsequent passes through a single gain medium so that a reproducibly stable beam size is achieved within the gain region. A resonator or a White Cell cavity is provided, including two or more mirrors (planar or curvilinearly shaped) facing each other along a resonator axis and an optical gain medium positioned on a resonator axis between the mirrors or adjacent to one of the mirrors. In a first embodiment, two curvilinear mirrors, which may include adjacent lenses, are configured so that a light beam passing through the gain medium and incident on the first mirror is reflected by that mirror toward the second mirror in a direction approximately parallel to the resonator axis. A light beam translator, such as an optical flat of transparent material, is positioned to translate this light beam by a controllable amount toward or away from the resonator axis for each pass of the light beam through the translator.

Abstract: A laser material for a solid-state laser that, when pumped by light having a wavelength in a suitable pump band, emits electromagnetic radiation having a wavelength lying in the range 2.0.ltoreq..lambda..ltoreq.2.1 .mu.m. The laser host material includes thulium-doped lutetium yttrium aluminum garnet (Tm:LuYAG) of approximate chemical composition (Tm.sub.x (Y.sub.w Lu.sub.1-w).sub.1-x).sub.3 Al.sub.5 O.sub.12, with x lying approximately in the range 0.01.ltoreq.x.ltoreq.0.5 and w lying in the range between 0.01 and 0.99. In particular, the Tm:LuYAG material produces light with wavelengths in the range .lambda.=2.020-2.024 .mu.m, where the normally-absorbing atmosphere has a transmission window with markedly reduced (or, alternatively, markedly enhanced) absorption. Another suitable group of laser materials has the chemical composition (Tm.sub.x (Y.sub.w Lu.sub.1-w-z Sen.sub.z).sub.1-x).sub.3 Al.sub.5 O.sub.12, with x lying approximately in the range 0.01.ltoreq.x.ltoreq.0.5, w lying in the range 0.01.ltoreq.

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 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: Apparatus and method for modulating the phase or the amplitude of a monochromatic light beam, the apparatus including in one embodiment a Mach-Zehnder interferometer that consists of two beam splitters or beam combiners, a fully reflective mirror and an electro-optical crystal for modulation of one of two beam components. The electro-optical crystal serves as an optical resonator for the portion of the light beam admitted into the crystal material, using total internal reflection of the light beam from two or more of the crystal surfaces. The crystal has a high finesse so that a relatively small change in voltage applied across the crystal produces a large (.apprxeq.180.degree.) change in the external phase shift associated with the modulated component of the light beam.

Abstract: In a laser, the laser gain member is optically pumped by a semiconductive source of pumping radiation having an elongated output beam aperture such as that provided by a single-wide stripe diode or diode array. The elongated beam of optical pumping radiation is twice reflected from a concave surface at non-normal angles of incidence and then focused onto the laser gain material for pumping same. The reflections serve to differentially focus rays diverging in the vertical plane from rays diverging in the horizontal plane to shape the pumping beam for improved pumping efficiency in the pumped mode volume of the laser gain material. In a preferred embodiment, a magnifying lens is disposed inbetween the source and the reflectors for decreasing the divergence of the pumping beam.

Abstract: An optical resonator, preferably of a solid state laser, is tuned by one or more sheets of piezo-electric material bonded to one or more tuning facets of an optically transparent solid state member portion of the resonator. A tuning voltage applied across the piezo-electric sheet tends to change the area of the bonded interface of the sheet to generate a set of tuning forces predominantly in the plane of the surface of the tuning facet. These tuning forces are transmitted through the tuning facet into the solid state portion of the optical resonator to produce a change in its refractive index and dimensional change which tunes the frequency of the optical resonator and the laser using same, if any. In a preferred embodiment, the piezo-electrically tuned optical resonator is an optically pumped ring resonator made of a lasant material such as Nd:YAG for tuning the output frequency of the ring laser.