Abstract: An authentication system and associated method including a substrate including one or more doped inclusions disposed in or on the substrate at one or more portions of the substrate such that electromagnetic radiation absorption and reflectance varies between a portion of the substrate in which a doped inclusion is disposed and a portion of the substrate in which no doped inclusion is disposed, and a detector including an electromagnetic radiation source configured to irradiate the substrate with electromagnetic radiation at multiple wavelengths and an imaging system configured to acquire multiple images of the substrate subjected to irradiation.

Abstract: This invention relates to a tunable amplified spontaneous emission (ASE) laser source comprising at least two laser sources excited by a single pump laser. More particularly, the present invention relates to a tunable amplified spontaneous emission (ASE) laser source comprising at least two laser sources excited by a single pump laser wherein said at least two laser sources each comprise an organic laser or a cascaded organic laser. The invention is used for providing a tunable amplified spontaneous emission (ASE) laser source comprising at least two laser sources excited by a single pump laser.

Abstract: The present invention provides a Group III nitride semiconductor light-emitting device exhibiting improved emission output. The light-emitting device comprises an n-type contact layer on which an n-electrode is formed, a light-emitting layer, an n-type cladding layer formed between the light-emitting layer and the n-type contact layer. The n-type cladding layer has a structure of at least two layers including a first n-type cladding layer closer to the light-emitting layer and a second n-type cladding layer farther from the light-emitting layer than the first n-type cladding layer. The first n-type cladding layer has a Si concentration higher than that of the second n-type cladding layer, and the first n-type cladding layer has a thickness smaller than that of the second n-type cladding layer.

Abstract: The invention provides a laser converter for converting a laser radiation of shorter wavelength to a laser radiation of longer wavelength using a single stage conversion. The laser converter comprises a laser diode for emitting a laser radiation in a first wavelength range, a cylindrical microlens for transferring and focusing the laser radiation to a laser chip and the laser chip for absorbing the laser radiation and emitting the laser radiation in a second wavelength range.

Abstract: A quantum device includes a resonator and a tuning structure. The tuning structure is made a material such as a chalcogenide and is positioned to interact with the electromagnetic radiation in the resonator so that a resonant mode of the first resonator depends on a characteristic of the tuning structure. The resonator is optically coupled so that a transition between quantum states associated with a defect produces electromagnetic radiation in the resonator. The characteristic of the tuning structure is adjustable after fabrication of the resonator and the tuning structure.

Abstract: A laser projector includes a green laser, a two-wavelength laser, a PBS, a collimator lens, a two-axis galvanometer mirror, a group of lenses, and a screen. The green laser emits a green laser beam. The two-wavelength laser emits red and blue laser beams. The PBS is provided at the position where respective optical paths of laser beams emitted from respective lasers cross each other to cause these optical paths to coincide with each other.

Abstract: A method of fabricating a color laser, comprising growing a first thin layer of ionic crystal on a substrate. The crystal can comprise many types of ionic crystals, such as sodium chloride or potassium chloride. A second thin layer of a different type of ionic crystal can be deposited above the first ionic crystal layer, such as lithium fluoride or sodium fluoride. An inert metal layer can be deposited between the first and second layers of ionic crystal and above the second layer of ionic crystal. When the first and second ionic crystal layers are radiated with gamma rays, they form color centers at the spots radiated. Because of the difference in crystalline properties of the two different ionic crystal centers, their color centers have different wavelengths. Each of the ionic crystal layers emit light at different characteristic wavelengths when illuminated at their unique absorption frequencies, and can be made to lase separately.

Abstract: A material having a surface and a dopant in the material distributed whereby the material has a spatially variant optical flux density profile. In accordance with the invention, tailored non-uniform gain profiles within a Yb:YAG laser component (rod, slab, disc, etc.) are achieved by a spatial material modification in the spatially masked pre-forms. High temperature-assisted reduction leads to the coordinate-dependent gain profiles, which are controlled by the topology of the deposited solid masks. The gain profiles are obtained by reducing the charge state of the laser-active trivalent Yb3+ ions into inactive divalent Yb2+ ions. This valence conversion process is driven by mass transport of ions and oxygen vacancies. These processes, in turn, affect the dopant distribution throughout the surface and bulk laser crystal.

Abstract: A white light-emitting lamp (1) includes a light-emitting portion (9) which is excited by light emitted from a semiconductor light-emitting element (2) to emit white light. The light-emitting portion (9) contains a blue phosphor, a yellow phosphor and a red phosphor. The yellow phosphor is composed of a europium and manganese-activated alkaline earth silicate phosphor having a composition expressed by (Sr1-x-y-z-u, Bax, Mgy, Euz, Mnu)2SiO4 (0.1?x?0.35, 0.025?y?0.105, 0.025?z?0.25, 0.0005?u?0.02).

Abstract: Emissive quantum photonic imagers comprised of a spatial array of digitally addressable multicolor pixels. Each pixel is a vertical stack of multiple semiconductor laser diodes, each of which can generate laser light of a different color. Within each multicolor pixel, the light generated from the stack of diodes is emitted perpendicular to the plane of the imager device via a plurality of vertical waveguides that are coupled to the optical confinement regions of each of the multiple laser diodes comprising the imager device. Each of the laser diodes comprising a single pixel is individually addressable, enabling each pixel to simultaneously emit any combination of the colors associated with the laser diodes at any required on/off duty cycle for each color. Each individual multicolor pixel can simultaneously emit the required colors and brightness values by controlling the on/off duty cycles of their respective laser diodes.

Abstract: A color-mixing laser module is disclosed, which is comprised of a laser unit capable of emitting red, blue and green laser beams; a beam combiner, for receiving and converging the laser beams emitted from the laser unit and then directing the converged laser light to illuminate on a light pattern adjusting unit; and the light pattern adjusting unit, capable of receiving the converged laser light from the beam combiner for adjusting the pattern of the same.

Abstract: A thin layer of ionic crystal is grown on a substrate. The crystal could be any type of ionic crystal, such as sodium chloride or potassium chloride. The crystal is a pure form of the chosen compound and may contain contaminants which would shift the wavelength of created color centers. On top of the first crystal layer, a second thin layer of a different type of crystal is deposited, such as lithium fluoride or sodium fluoride. When these two layers are radiated with gamma rays, they will each form color centers at the spots radiated. Because of the difference in crystalline properties of the two different ionic crystal centers, their color centers would be at different wavelengths. Each of the two separate ionic crystals will emit light at different characteristic wavelengths when illuminated at their unique absorption frequencies. Each layer can be made to lase separately.

Abstract: This invention is about a window interface layer in a light-emitting diode which comprises an n-type GaAs substrate with an n-type ohmic electrode at the bottom side thereof; an n-type AlGaInP cladding layer formed atop the substrate; an undoped AlGaInP active layer formed atop the n-type cladding layer; a p-AlGaInP cladding layer formed atop the active layer; a p-type window layer made of GaP; a p-type ohmic electrode formed atop the p-type window layer; and a highly doped p-type interface layer made of GaxIn1-xP (0.6?x?0.9) and interposed between the p-type cladding layer and p-type window layer wherein the highly doped p-GaInP interface layer possesses a band gap which is higher than that of the active layer and, however, smaller than that of the p-type cladding layer, and wherein the lattice constant lies between GaAs and GaP.

Abstract: A III-V nitride semiconductor laser device demonstrates an excellent emission characteristic without an increase in production cost. The refractive index of a p-side optical guiding layer is larger than that of an n-side guide layer.

Abstract: External cavity laser with reflector in optical wave guide, particularly HDBR laser, with an active element comprising a semiconductor optical amplifying cavity having a low-reflectivity facet (3), for example a Semiconductor Optical Amplifier (SOA) with a facet (30) opposite to said low-reflectivity facet treated with a reflecting coating, or a Fabry-Perot laser, and an external reflector comprising a Bragg grating (70) formed in an optical wave guide (4) near a termination (5), facing said facet, of a segment (5, 6, 7) of said optical wave guide coupled with the facet. The grating has a spatial profile of modulation of the refraction index such that a corresponding optical reflectivity spectrum (A) has an optical bandwidth (W) sufficiently small around a prescribed laser oscillation mode wavelength (?c) for the laser to oscillate only on the prescribed mode and not on other oscillation modes even in conditions of high-frequency direct modulation.

Abstract: An organic vertical cavity laser device includes a substrate; a bottom dielectric stack reflective to light over a predetermined range of wavelengths and being disposed over the substrate, and an organic active region for producing laser light. The device also includes a top dielectric stack spaced from the bottom dielectric stack and reflective to light over a predetermined range of wavelengths, and a thermally conductive transparent layer disposed between the bottom dielectric stack and the organic active region or between the top dielectric stack and the organic active region or both.

Abstract: The semiconductor laser element comprises, from bottom to top, the p-AlxGa1?xAs upper clad layer, p-AlyGa1?yAs resistance control layer, and p-GaAs cap layer (where x>y>0.2). A portion of only the resistance control layer and cap layer is selectively etched. The etchant used for this etching is a mixture of organic acid and hydrogen peroxide based mixture, has such a composition such that the ratio of dissolution rate of the upper clad layer to the cap layer is between 10 and 20, and pH is between 7.4 and 7.6.

Abstract: The nitride semiconductor layer structure comprises a buffer layer and a composite layer on the buffer layer. The buffer layer is a layer of a low-temperature-deposited nitride semiconductor material that includes AlN. The composite layer is a layer of a single-crystal nitride semiconductor material that includes AlN. The composite layer includes a first sub-layer adjacent the buffer layer and a second sub-layer over the first sub-layer. The single-crystal nitride semiconductor material of the composite layer has a first AlN molar fraction in the first sub-layer and has a second AlN molar fraction in the second sub-layer. The second AlN molar fraction is greater than the first AlN molar fraction. The nitride semiconductor laser comprises a portion of the above-described nitride semiconductor layer structure, and additionally comprises an optical waveguide layer over the composite layer and an active layer over the optical waveguide layer.

Abstract: Semiconductor laser diodes, particularly high power ridge waveguide laser diodes, are often used in opto-electronics as so-called pump laser diodes for fiber amplifiers in optical communication lines. To provide the desired high power output and stability of such a laser diode and avoid degradation during use, the present invention concerns an improved design of such a device, the improvement in particular consisting of novel design of the ridge waveguide of the laser. Essentially the novel design consists in a segmented ridge waveguide having at least two straight segments, i.e. segments with constant, but different cross sections or widths, and at least one flared segment connecting the two different straight segments. A further improvement can be achieved by combining this approach with a laser diode design termed “unpumped end sections” and described in copending U.S. patent application Ser. No. 09/852,994, entitled “High Power Semiconductor Laser Diode”.

Abstract: A thin layer of ionic crystal is grown on a substrate. The crystal could be any type of ionic crystal, such as sodium chloride or potassium chloride. The crystal is a pure form of the chosen compound and may contain contaminants which would shift the wavelength of created color centers. On top of the first crystal layer, a second thin layer of a different type of crystal is deposited, such as lithium fluoride or sodium fluoride. When these two layers are radiated with gamma rays, they will each form color centers at the spots radiated. Because of the difference in crystalline properties of the two different ionic crystal centers, their color centers would be at different wavelengths. Each of the two separate ionic crystals will emit light at different characteristic wavelengths when illuminated at their unique absorption frequencies. Each layer can be made to lase separately.

Abstract: A resonating cavity system of a tunable multi-wavelength semiconductor laser. The system has a laser, a collimating lens, a grating, a slit plate, and adjustable mirrors. The laser has two ends. The first end is coupled to the cavity, and the second end outputs the laser beam. The grating is located in the lasing path between the first end of the semiconductor laser and the plate, and the plate is located before the adjustable mirrors. Each adjustable mirror is aligned to the corresponding slit of the plate. Lasing paths extend from the first end of the laser, through the grating, the lens, a plurality of the slits of the plate, to the adjustable mirrors. Each mirror can be adjusted independently to ensure each beam is reflected accurately back to each resonating path. Thereby, a feature of equal lasing gains of all the resonating paths is guaranteed.

Abstract: An apparatus having an output register coupled to a content addressable memory (CAM) array. The output register may be configured to output data based on a delayed clock signal. A programmable delay circuit may be coupled to receive a reference clock signal and generate the delayed clock signal using one or more delay elements.

Abstract: A glass-ceramic which is substantially and desirably totally transparent, and which contains a predominant crystal phase of forsterite. The glass-ceramic is formed from precursor glasses having the following compositions, in weight percent on an oxide basis: SiO2 30-60; Al2O3 10-25; MgO 13-30; K2O 8-20; TiO2 0-10; and GeO2 0-25. The glass-ceramic may be doped with up to 1 wt. % chromium oxide to impart optical activity thereto.

Abstract: A color mixing system is proposed for use in an optical-fiber laser-diode assembly comprising at least two semiconductor laser diodes, optical fiber light input and output couples, a system of spatial superposition of laser beams of different wavelength with at least one semi-transparent mirror, and a system for electronic control of light power in monochromatic light components to be mixed. The electronic control system makes it possible to produce a plurality of different colors. The basic colors, i.e., blue, green, and red, are produced by respective laser diode assemblies provided with means for adjusting output light power on each individual assembly. The electronic system contains a microprocessor connected to a pulse width modulation unit capable of modulating the duration and shape of the light pulse emitted from the laser diode. This allows for selecting a required ratio of energetic brightnesses of light beams produced by individual laser diode assemblies.

Abstract: Disclosed are methods and apparatus for at least one of authenticating, sorting or counting documents, as well as to security structures contained within documents and to documents containing security structures. A security device or structure includes an optical gain medium and a structure having boundaries that impart an overall geometry to the structure that, in combination with at least one material property of the structure, supports an enhancement of electromagnetic radiation emitted from the gain medium for favoring, in one embodiment, the creation of at least one mode that enhances an emission of electromagnetic radiation within a narrow band of wavelengths. Suitable, but not limiting, shapes for the structure comprise elongated, generally cylindrical shapes such as filaments, a sphere shape, a partial-sphere shape, a toroidal shape, a cubical and other polyhedral shape, and a disk shape.

Abstract: The semiconductor laser element comprises, from bottom to top, the p-AlxGa1-xAs upper clad layer, p-AlyGa1-yAs resistance control layer, and p-GaAs cap layer (where x>y>0.2). A portion of only the resistance control layer and cap layer is selectively etched. The etchant used for this etching is a mixture of organic acid and hydrogen peroxide based mixture, has such a composition such that the ratio of dissolution rate of the upper clad layer to the cap layer is between 10 and 20, and pH is between 7.4 and 7.6.

Abstract: A diode pumped, multi axial mode, intracavity doubled, intracavity tripled laser, includes at least two resonator mirrors defining a resonator cavity. A laser crystal and a doubling crystal are positioned in the resonator cavity. A tripling crystal is also positioned in the resonator cavity. A diode pump source supplies a pump beam to the laser crystal and produces a laser crystal beam with a plurality of axial modes that are incident on the doubling crystal. This produces a frequency doubled output beam. Further, a diode pumped, multi axial mode, intracavity nonlinearly-converted laser is provided and includes at least two resonator mirrors defining a resonator cavity, a laser crystal and a nonlinear conversion apparatus positioned in the resonator cavity. A nonlinear conversion apparatus is also positioned in the resonator cavity.

Abstract: A semiconductor laser capable of producing a high optical output has a coating film applied to an exit end. The coating film has a refractive index (n1) which is large compared with the refractive index (neff) of a semiconductor waveguide. The refractive index (n1) and the refractive index (neff) satisfy the relationship: n12>neff.

Abstract: This invention provides compact, fixed-wavelength and tunable fiber-optic lasers comprising a gain medium, for example a semiconductor, half-cavity VCSEL, or an organic light emitting polymer, within a Fabry-Perot cavity wherein one of the mirrors forming the cavity is a mirror integral with a fiber, for example a mirror (metallic or dielectric, for example) deposited at a fiber end, a reflective tap within an optical fiber, a fiber Bragg Grating (FBG), or a fiber loop mirror. Semiconductor gain material can be bulk semiconductor material or comprise a semiconductor multiple quantum well region. The gain medium itself is not confined to a fiber.

Abstract: The present invention is directed to a tunable, solid state laser utilizing room temperature, stable, color centers of LiF:F.sub.2.sup.+ ** material. Also disclosed is a method of lasing. An object of the present invention is to develop and optimize LiF:F.sub.2.sup.+ ** thermostabilized active media, to propose a method of pumping, and to realize a room temperature, stable and efficient operation of the color center laser. These and other objects are achieved by introducing special dopants in the crystal at the stage of crystal growing; applying special regimes of ionizing treatment of the crystal, resulting in thermostabilization of the F.sub.2.sup.+ centers in LiF crystals; and utilizing alexandrite laser radiation for color center crystal pumping with a pump radiation frequency which is appropriate for the selective excitation of the F.sub.2.sup.+ color centers.

Abstract: In a color-center light source, a color center is formed artificially. A predetermined single atom is removed from the surface of a defect-free ionic crystal so as to form a lattice defect. Optical transition of the defect is utilized so that it functions as a light source.

Abstract: An optical switch includes a dual-core optical fibre coupler having waveguides which are erbium doped, silica-based fibre amplifiers. The waveguides are pumped by pump lasers which are used to control the mean differential gain of the waveguides to be zero or a first value at which two values the linear coupler is a cross-coupler or a through-coupler at an operating wavelength.

Abstract: A device for optically storing and retrieving information incorporating a cadmium fluoride crystal. Using focused ionizing radiation, patterns can be formed in the crystal by the creation of color centers and/or intrinsic luminescence quenched areas. The stored information can then be retrieved by irradiating the crystal with visible light, ultraviolet light, ionizing radiation or combinations thereof. The device and the storage technique allows the storage of various different levels of information, the different levels being retrievable by using different irradiating media and magnifications of the retrieved information. The device and technique also allows the information to be stored for a predetermined period of time.

Abstract: A solid state laser is provided having as the laser medium diamond and an optically active dopant element which is found to lase in the solid matrix. The dopant is preferably titanium, vanadium, chromium, iron, cobalt, nickel, zinc, zirconium, niobium, cadmium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and uranium. Erbium is especially preferred. The laser medium is formed as dopants are added by ion implantation to a diamond crystal as the diamond is grown by chemical vapor deposition.

Abstract: An ultraviolet solid state laser includes: (a) a laser cavity defined by a et of opposing mirrors, (b) a laser medium disposed in this laser cavity, where this medium includes a LiSrAIF.sub.6 (LiSAF) host material doped with enough cerium ions to produce a longitudinal mode laser emission when this laser medium is pumped; and (c) a source of pumping radiation.

Abstract: Disclosed is the use of Sc.sup.2+ based active crystalline luminescent media for laser systems, tunable in the UV-visible spectral range. The crystalline media are Sc-doped alkali-earth-halide crystals such as: (1) alkali-earth-halide combinations, such as MeF.sub.2, MeCl.sub.2,crystals; (2) mixed alkali-earth metal fluorides and chlorides, such as MeFCl, M.sub.x Me.sub.1-x F.sub.2 and M.sub.x Me.sub.1-x Cl.sub.2 crystals; and (3) complex fluoride crystals; wherein M and Me are Ca, Sr, Ba or Mg. These crystals have Sc.sup.2+ ion impurities providing stable optical centers that yield advantageous luminescent properties. The base crystal structure utilized determines the luminescent emission spectrum for the Sc.sup.2+ optical centers. By manipulating the base crystal, the maxima of the absorption and emission bands may be altered from UV-blue to red in the optical spectrum. The Sc.sup.2+ active crystalline luminescent media are initially doped with trivalent Sc.sup.3+ ions during crystal growth.

Abstract: The subject invention relates to a new regime of lasing--superbroadband or pre-assigned spectral composition lasing. A new cavity construction and application of room temperature operable LiF color center crystals provide generation with a spectral width in one pulse practically coinciding with the luminescence spectrum of the active medium.

Abstract: A gain medium is comprised of a multi-phase system wherein: a first phase is an electromagnetic radiation emission phase; a second phase is an electromagnetic radiation scattering phase; and a third phase is a transparent matrix phase. By example, the emission phase may consist of dye molecules, the scattering phase may consist of high contrast particles, and the matrix phase may consist of a solvent such as methanol. In some embodiments of this invention the emission and scattering phases may be the same phase, as when semiconductor particles are employed. A smallest dimension of a body comprised of the gain medium may be less than a scattering length associated with the scattering phase. It is shown that nearly thresholdless laser behavior is observed in strongly scattering optically pumped dye-methanol solutions containing colloidal TiO.sub.2 or Al.sub.2 O.sub.3 ruby nanoparticles.

Abstract: A laser source which operated under the principals of cooperative unconversion produces controllable optical pulses at wavelengths which are shorter than the wavelength of the laser energy which pumps the gain medium. The source is a solid-state laser which employs a five percent Er:LiYF.sub.4 crystal which is arranged in an astigmatically-compensated 3-mirror cavity. Pumping is achieved at 1.5 microns in the infrared, and the system operates in a continuous-wave, mode-locked fashion in the green spectral region at approximately 544 nm. The cooperative inversion mechanism involves energy pooling by trios of excited rare earth dopant ions in the laser medium. Q-switching is achieved with the use of intracavity amplitude modulation so as to achieve three-fold upconversion. A 3-mirror astigmatically-compensated cavity with the gain medium permits modulation of losses in a manner which cannot be achieved with known systems and achieves high stability.

Abstract: A color center laser is provided with a crystal disposed within a longitudinally pumped cavity. Optics are provided to transversely excite the crystal. Both a circular lens and a cylindrical lens focus an auxiliary beam into the crystal of the color center laser to produce (F.sub.2.sup.+).sub.A color centers for lasing. The cylindrical lens is used to focus the auxiliary beam to a narrow focal line. The circular lens is used to adjust the length of the focal line. By adjusting the length of the focal line, an entirety of the pump beam is used for excitation. The lenses thus collimate and focus the focal line to a length within an active volume in the crystal of the color center laser essentially equal to a length of the crystal.

Abstract: A powerful and stable color center laser is provided by additively colored NaCl:OH.sup.- crystals. The OH.sup.- impurity is the key dopant for creating color center lasing in NaCl, providing an output tunable over the 1.41 to 1.81 .mu.m region. In addition, modelocked pulses of 5 psec duration are available in a synchronously pumped arrangement, tunable from 1.47 to 1.73 .mu.m.

Abstract: The laser material of the invention comprises an alkali-halide crystal, with a rocksalt crystallographic structure, containing point defects selected from the group consisting of F.sub.3 or R, F.sub.4 and N.sub.2 color centers. The preferred laser material is based on the neutral "N.sub.2 " color center defect. The alkali halide can be any alkali halide, for example, lithium, sodium, potassium and rubidium chloride, bromide and fluoride. The preferred alkali halide is potassium chloride. The lasers of the invention comprise a stable near-infrared laser which can be tuned in the case of KCl for example from 1.23 to 1.35 .mu.m, and can be optically pumped at 1.06 .mu.m, for example from a Q-switched Nd:YAG laser. The laser of the invention represent the first reported laser based on N.sub.2 -center transitions, and appear to be the first stable laser using a charge-neutral color center in pure alkali halide hosts.

Abstract: A method of manufacturing a diamond laser crystal having an excellent laser efficiency is performed by first, preparing a synthetic type Ib diamond containing at least 60 volume percent of a (111) plane growth sector (43) is prepared. This synthetic diamond is then thermally treated under high temperature/high pressure, so that type Ib nitrogen contained in the synthetic diamond is converted to type IaA nitrogen. Thereafter an electron beam is applied to the synthetic diamond in order to generate vacancies in the synthetic diamond. Finally annealing is performed on the synthetic diamond to form H3 centers by coupling the type IaA nitrogen atoms contained in the synthetic diamond, with the vacancies. According to this method, the H3 centers can be formed in the synthetic type Ib diamond at high concentration, while formation of NV centers which become an obstacle to laser action, can be suppressed.

Abstract: A diamond laser formed of a synthetic diamond provides a high output power and a variable wavelength in the near infrared region. The maximum value of the optical density of H2 centers in the direction of the pumping light is in the range of 0.01 to 4. Laser action is caused in the range of 1000 to 1400 nm by an external pumping light at 650 to 950 nm. Such a diamond laser is produced by preparing a synthetic Ib type diamond having a nitrogen concentration within the range of 1.times.10.sup.17 to 8.5 10.sup.19 atoms/cm.sup.3, subjecting this synthetic diamond to an electron irradiation with a dose of not less than 5.times.10.sup.17 electrons/cm.sup.2, and heat-treating the synthetic diamond in a vacuum of not more than 1 Torr or in an inert gas atmosphere and at a temperature within the range of 1400.degree. to 1850.degree. C.

Abstract: A light emitting element comprising diamond which contains N-V color centers in a maximum optical density of of 0.01 to 3.5 in a direction of excitation light, Ib type nitrogen atoms in a maximum optical density not larger than 0.2 in a wavelength range of 530 to 610 nm and optionally H3 color centers, which element can be efficiently produced from artificial diamond by a combination of irradiation by an electron beam or a neutron beam and annealing.

Abstract: (F.sub.2.sup.+).sub.A color centers can be produced in additively-colored KI:Li or RbI:Li crystals provided that the material is colored in a nitrogen-free atmosphere. Copious (F.sub.2.sup.+).sub.A centers are produced in lithium-doped KI:Li or RbI:Li crystals using a procedure in which the crystals are grown, additively colored, and annealed in an argon ambient; and optically excited at successively-lower temperatures with a light of a wavelength readily absorbed by the crystal situated in a vacuum.

Abstract: Optical fibres comprised of a halide glass incorporating color centers, for example fluoride fibres, can behave as a laser or an amplifier when maintained at a low temperature, typically 77.degree. K., and optically pumped. A laser may be comprised by a length of such a fibre (1) wound on a spool (2) and disposed in liquid nitrogen (4), the ends of the fibre are outside of the coolant and associated with input and output mirrors (5,6) which define the extremities of a lasing cavity. An optical pumping signal (7) is provided by a laser (8), for example a Krypton ion laser operating in the visible range. The output of the fibre laser is in the infra-red. Higher gain than with conventional color center lasers is achieved due to the longer interaction length and cooling problems are overcome.

Abstract: A powerful and stable color center laser is provided by additively colored NaCl:OH.sup.- crystals. The OH.sup.- impurity is the key dopant for creating color center lasing in NaCl, providing an output tunable over the 1.41 to 1.81 .mu.m region. In addition, modelocked pulses of 5 psec duration are available in a synchronously pumped arrangement, tunable from 1.47 to 1.73 .mu.m.

Abstract: A passive laser Q-switch is fabricated from a crystal which can form saturable color centers, such as lithium fluoride. The arbitrarily long crystal is irradiated with electrons from the side, or radially, to impart a radial distribution of saturable color centers therein, with the highest density at the periphery of the crystal. Optionally, the crystal can also be irradiated axially with electrons or in any direction with another form of radiation having greater penetration into the crystal, such as gamma radiation, to establish a base level of saturable color centers throughout the crystal. The crystal having the radial distribution of color centers acts as a Q-switch, but additionally tends to reduce beam divergence and increase the brightness of the laser beam by virtue of the nonlinear bleaching mechanism.

Abstract: An optical fibre for use in fibre lasers has the lasing additive eg Er.sup.3+, concentrated in center of the core. Preferably the core has an inner region which contains the additive and an outer region which is dopant free. The concentration of the dopant reduces the pump threshold for a laser and improves the gain performance for a given pump power. The fibre is conveniently made in MCVD. The use of Al.sub.2 O.sub.3 in the inner zone appears to reduce loss of dopant during tube collapse.