Abstract: A laser includes a chamber having a front mirror and a back mirror defining a optical propagation path. An optical gain medium such as a solid state disk, rod or slab is located between the front and back mirrors within the chamber to produce a laser light along the optical propagation path. A birefringent lens formed from an optically active material is located within the chamber to simultaneously focus the laser light and to affect the polarity of the laser light as the light passes through the birefringent lens.

Abstract: A semiconductor laser module has a Fabry-Perot type semiconductor laser device, an optical fiber, and first and second lenses. The tip of the optical fiber, on which the laser beam falls, is askew polished. The optical fiber is fixed in such a manner that the axis of the optical fiber makes an angle with respect to an optical axis of the laser beam. Coatings that avoid reflection are formed on the tip of the optical fiber, and on the first and second lenses.

Abstract: A dual wavelength optical fiber distributed feedback laser comprises a pump laser coupled to a birefringent fiber in which a first grating device (two co-located single phase-shift fiber Bragg gratings (FBGs)) is provided. The grating device gives the laser two potential lasing modes in each of two orthogonal polarization states. A polarization mode coupling FBG selects two orthogonally polarized modes on which the laser oscillates. In a photonic data carrying signal source, the laser is coupled to a polarization dependent, optical modulator operable to apply a modulation, at a data signal frequency, to one polarization mode of the laser output. In an optical waveguide based electronic signal transmission system the modulated and un-modulated polarization modes output from the source are transmitted across a fiber transmission line to a polarizing optical fiber in which the two modes heterodyne to generate an electronic carrier signal in the optical domain.

Abstract: The invention pertains to wavelength-agile optical filters suitable for wavelength-division-multiplexed (WDM) optical communications networks. More particularly, the invention pertains to optical filters with a wavelength reference that can be remotely switched to arbitrarily selectable channels on a standard grid, and to re-configurable optical communications networks employing same. The present invention provides a communication apparatus with a tunable filter which may be used in a wide range of applications including tuning an external cavity laser (ECL), selecting a wavelength for an add/drop multiplexer and providing channel selection and feedback for a wavelength locker. The filter may be utilized as a discrete component or in combination with circulators, wavelength lockers and gain medium. The filter may be implemented in whole or in part as part of a gain medium.

Abstract: Apparatus and methods that utilize tunable elements to provide for selective wavelength tuning of a light beam. The apparatus comprises a first tunable wavelength selection element having a first adjustable free spectral range, a second tunable wavelength selection element having a second adjustable free spectral range, with the first and second tunable wavelength selection elements configured to define a tunable joint transmission peak. The first and second tunable wavelength selection elements respectively define first and second pluralities of tunable transmission peaks, wherein respective ones of each of the first and second plurality of transmission peaks are aligned to obtain a joint transmission peak that may be adjusted by tuning the wavelength selection elements. The free spectral ranges of the wavelength selection elements are configured to enable a Vernier tuning effect.

Abstract: An optical resonator supporting two sets of simultaneously co-existent oscillation modes (30 and 31), having polarizations orthogonal to each other. Mode control elements (28 and 29), such as apertures and phase elements, are introduced into the resonator to allow only preferred modes to exist. The placement and orientation of the sets are designed such that the high intensity zones of one set fall on the nodes or low intensity zones of the other set in an interlaced pattern. Thus, in a laser resonator, better utilization of the gain medium (24) is achieved and the beam quality and brightness over multimode lasing are improved. This configuration improves the performance of high Fresnel number resonators, in both pulsed and continuous lasers, for applications such as scribing, drilling, cutting, target designation and rangefinding. An application of the intra-cavity coherent summation of orthogonally polarized modes is described, whereby azimuthally or radially polarized beams may be obtained.

Abstract: A single frequency filter for a laser, comprising a polarizer that defines a direction of polarization and one or more birefringent elements situated within the cavity with their dielectric axes offset from the direction of polarization. The ends of the birefringent elements have a finite reflectance, and may be coated for reflectance or left uncoated. In some embodiments the filter is situated in a laser cavity with a broadband gain medium, in other embodiments, the filter is situated in an external cavity. To provide tunability, a wavelength control system is coupled to the birefringent element. An embodiment is described in which the filter comprises two birefringent elements of unequal optical length along the optical axis, which advantageously reduces the voltage required to tune the frequency. To provide tunability, the first and second birefringent elements are both coupled to a wavelength control system that simultaneously controls both elements.

Abstract: Light emission methods and light emission devices are described including method and devices capable of emitting light at a plurality of controllable wavelengths. According to one aspect, a light emission method includes providing a control signal and emitting light using a laser operating in a plurality of polarization states. The polarization state of the laser is adjusted responsive to the control signal and the wavelength of the light emitted using the laser is adjusted responsive to the adjustment of the polarization state of the laser.

Abstract: An optical resonant cavity (50) defined between two mirrors (13′, 40), one of which (40) is a variable pitch Bragg reflector grating, is characterized in that a parameter CS of variation of the Bragg wavelength of the grating is such that the cavity resonates continuously from a first optical frequency to a second optical frequency higher than the first optical frequency. The invention can be used in particular to produce broadband band-pass filters with steep flanks, broadband amplifiers with no gain fluctuation, and continuous emission spectrum lasers and light-emitting diodes.

Abstract: A method for generating polarized laser output radiation utilizes a laser resonator whose active medium exhibits thermally induced birefringence. The radiation fields oscillating in the laser resonator are not subjected to polarization selection, and only the radiation field exhibiting the desired polarization state (p) is partially output. Only a prescribed polarization of the radiation fields of the laser radiation which can oscillate in the resonator can be partially output from the resonator with a prescribed output level and all differently polarized radiation fields remain in the resonator in a completely reflecting fashion.

Abstract: A laser apparatus wherein a gain medium and an optical output assembly are mounted on a common, thermally conductive substrate which provides selective thermal control of the gain medium and output components on the substrate while avoiding unnecessary thermal control of other laser components, and methods for selectively cooling a gain medium and output components of a laser apparatus.

Abstract: Surface textures embossed in a substrate such as plastic include surface depressions or cones having equally-spaced, reflective terraced steps to support coherent reflections of incident light. A desired color or bandwidth of coherent reflected light off the terraced steps is produced by adjusting the index of refraction of a material in communication with the terraced steps of the substrate. Preferably, the index of refraction of each zone of terraced steps is controlled based on an applied electric field. Accordingly, light reflected from a plurality of controlled zones can be used to produce an image for an observer.

Abstract: The inventive rod includes a gain medium having first and second equal length portions sharing a common optical axis and an optical rotator disposed between said first and second portions which optical rotator compensates for birefringence. In an exemplary case, the optical rotator includes first and second waveplates optically coupled to one another and oriented with respect to one another by a predetermined angle, where the first waveplate receives a polarized beam having a first state, and the second waveplate produces the polarized beam having a second state, the first and second states differing from one another by 90°. Multiple rotators can be employed to compensate strongly birefringent rods, each rotator compensating a section of a rod constructed from a plurality of equal length optical gain elements.

Abstract: The present invention provides a semiconductor laser module. A semiconductor laser module (1A) comprising a semiconductor laser element (2a) and an optical fiber (3a) optically coupled by an optical coupling means (2b) is provided, wherein on the optical fiber (3a), a reflective portion (4) and a birefringence fiber (3a) are provided, the birefringence fiber (3a) is provided at least from the incident end on the side of the optical coupling means (2b) to immediately before the reflective portion (4), a connection portion (6) is provided at least at one point in the longitudinal direction of the birefringence fiber (3a), and in the connection portion (6), two eigen axes of X axes and Y axes are connected so that the eigen axes intersect each other at an established angle &thgr;.

Abstract: A diode pumped solid state laser/OPO system widely tunable in mid infrared spectrum for infrared matrix assisted laser desorption/ionization (MALDI) mass spectroscopy is disclosed. Up to a few tens of milli-Joule, short pulse, tunable near infrared laser pulse is generated from an all solid state laser at a high pulse repetition rate up to one kHz. The tunable near-infrared laser pumps a Quasi-Phase Matching (QPM) OPO system to further shift the wavelength to the mid-IR range and to broaden the tuning range to as much as 3 &mgr;m to effectively generate a widely tunable spectral output. The wide range tuning of the infrared output is accomplished by a narrow range tuning of the pump laser. The pump laser output is generated by a diode pumped tunable solid state laser module using either a Yb:YAG crystal or any other efficient tunable laser crystals. The wavelength range (2-5 &mgr;m) covered by the solid state laser system is optimum for MALDI applications.

Abstract: For the sake of no needing to provide a mechanically actuating section such as a rotating mechanism thereby to be capable of realizing stable ultrashort pulse laser oscillation, an ultrashort pulse laser oscillator comprises a laser resonator composed of a mirror on outgoing side, and a total reflection mirror; a continuous wave oscillation laser for inputting excitation laser beam; a tunable laser medium capable of laser oscillation; a photoacoustic optical crystal having birefringent property as a crystal for selecting wavelength to which is input outgoing light from the tunable laser medium; a piezoelectric element inputting an acoustic wave having a frequency in response to a distortion upon application of voltage; a power source for applying the voltage; and a control means for controlling a frequency of voltage to be applied to the piezoelectric element by the power source wherein a frequency of voltage to be applied to the piezoelectric element by the power source is controlled by means of the control

Abstract: Techniques and systems for monitoring a difference between the frequency of a laser and a resonance of a birefringent optical resonator. A feedback control loop may be used to lock the laser to the resonator, or alternatively, to lock the optical resonator to the laser.

Abstract: A deep-ultraviolet violet laser beam which is a harmonic and is generated inside a nonlinear optical element (101) is emitted outside the nonlinear optical element (101), being spaced from a green laser beam, which is a fundamental wave. The green laser beam emitted outside the nonlinear optical element (101) is reflected by an input-coupling mirror (102) and applied again into the nonlinear optical element (101) in order to form a closed optical path for the fundamental wave. Also, the deep-ultraviolet laser beam emitted outside the nonlinear optical element (101) is reflected by a reflecting mirror (28) other than the input-coupling mirror (102) in order to emit the deep-ultraviolet laser beam from a deep-ultraviolet laser beam-generating section (20).

Abstract: A method of filtering an input optical signal, the method including the step of: (a) utilising the phase response of a Gires-Tournois resonator to produce a corresponding spatial separation in a predetermined wavelength range of the input optical signal. The method further preferably can include the step of: (b) projecting substantially orthogonal beams onto the surface of a Gires-Tournois resonator at slightly different angles of incidence and utilising the phase difference in the phase response of the orthogonal beams to spatially separate the predetermined wavelength range. A birefringent wedge can be utilised to separate a polarised input beam into the substantially orthogonal beams for projection onto the surface of the Gires-Tournois resonator.

Abstract: A variable-wavelength semiconductor laser device containing a tapered-stripe semiconductor laser amplifier and a wavelength selection unit. Light emitted from a back end surface of the tapered-stripe semiconductor laser amplifier is incident on the wavelength selection unit. The wavelength selection unit selects a portion of the light having a specific wavelength, and returns the selected portion to the tapered-stripe semiconductor laser amplifier. The tapered-stripe semiconductor laser amplifier amplifies the returned portion of the light to emit the amplified light from a front-end surface of the tapered-stripe semiconductor laser amplifier. The wavelength selection unit is constructed so that the specific wavelength can be changed according to strength of an electric field applied to the wavelength selection unit. An electric field applying unit is provided for applying the electric field to the wavelength selection unit.

Abstract: A compound intercavity interferometer for a free-electron laser (FEL) comprising at least two beam splitters positioned at a predetermined angles with respect to optical pathways. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope of meaning of the claims.

Abstract: The invention provides a UV below 200 mm lithography method. The invention includes providing a below 200 mm radiation source for producing <200-nm light, providing a plurality of mixed cubic flouride crystal optical elements, with the fluoride crystals comprised of a combination of alkaline earth cations having different optical polarizabilities such as to produce an overall isotropic polarizability which minimizes the fluoride crystal spatial dispersion below 200 nm, transmitting <200-nm light through the cubic fluoride crystal optical elements, forming a lithography pattern with the light, reducing the litographic patter and projecting the lithography pattern with the cubic fluoride crystal optical elements onto a UV radiation sensitive lithography printing medium to form a printed lithographic pattern. The invention includes making the mixed fluoride crystals and forming optical element thereform.

Abstract: A laser arrangement comprising a ring cavity at least two gain portions in said ring cavity, an input-output coupling connected to said ring cavity, a discriminator means connected in said ring cavity and adapted to discriminate between a pumping signal and an output signal and pumping means for providing said pumping signal and connected to said gain portions of said ring cavity such that, upon activation of said pumping means, said laser arrangement operates as a laser producing a laser output at said input-output coupling.

Abstract: A laser system includes a travelling-wave active laser-resonator arranged for generating laser-radiation having a first wavelength and arranged such that the first-wavelength radiation circulates in only one direction therein. An optically-nonlinear element is positioned in the travelling-wave laser-resonator such that the first-wavelength radiation circulates therethrough. Radiation having a second-wavelength is injected into the optically-nonlinear crystal such that the first-wavelength radiation and second-wavelength radiation mix therein, thereby generating radiation having the sum-frequency of the first and second-wavelength radiations. The sum-frequency radiation from the optically-nonlinear element is delivered from the laser system as output-radiation. In one example, the travelling-wave resonator has a YVO4 gain medium generating radiation having a wavelength of about 1064 nm. The optically-nonlinear crystal is a CLBO crystal.

Abstract: A light source is disclosed. In one aspect, a gain region defined by a first and second mirror is provided having a corresponding resonant mode, and an external cavity defined by a third mirror and the second mirror is also provided having a plurality of resonant modes. A birefringent crystal is then disposed within said external cavity for the purpose of controlling the state of polarization.

Abstract: A low noise laser includes a birefringent gain crystal arranged so that polarization is not constant within the gain crystal. The gain crystal and an intracavity optical element each have a nonzero polarization retardance. The total single-pass retardance is approximately equal to an odd multiple of one-half wave; for example each may provide one quarter wave retardance. In one embodiment the optical element comprises a nonlinear crystal situated within the laser cavity for Type II frequency doubling. The principal crystal axis of the gain crystal is offset from the principal axis of the nonlinear crystal at an offset angle for example about 45°. In one embodiment a gain crystal and frequency-doubling crystal are coupled together to form a monolithic laser component. An alternative embodiment is described in which the optical element comprises a quarter-wave plate and the laser output includes substantially two linear polarizations at the fundamental wavelength.

Abstract: The invention provides a laser system for producing a high energy amplified laser beam output from an oscillator producing a wave front of low energy laser beam, the system including at least one amplifier positioned to receive the low energy laser beam for amplification via a first polarizer; a second polarizer, positioned along the axis of the amplified beam at the output side of the amplifier, for allowing a first fraction of the beam to pass therethrough and for reflecting a second fraction of the beam from an output surface of the polarizer, the second fraction constituting the output of the system; a retroreflector, associated with a quarter wave plate, oriented to receive the first fraction and to reflect it back toward the second polarizer, and reflecting means for reflecting the reflected first fraction toward the first polarizer to be reflected toward the amplifier for further amplification and to be reflected off the output surface of the second polarizer together with the second fraction.

Abstract: An F2-excimer laser has multiple closely-spaced spectral lines of interest around 157 nm, and one of the lines is selected by wavelength selection optics. The wavelength selection optics of a first preferred embodiment include a birefringent Brewster window enclosing the laser gas volume of the discharge chamber. The window preferably comprises MgF2 and is located at one end of the discharge chamber. One line is selected of the two when the optical thickness of the window is selected in coordination with rotatably adjustable, orthogonal refractive indices of the window. The transmissivity of the window is dependent on the orthogonal refractive indices and the optical thickness of the window. The wavelength selection optics of a second preferred embodiment include are at least partially within the laser active volume. In this way, line selection is performed in a manner which optimizes the combination of optical and discharge efficiency, resonator size and cost.

Abstract: An optical assembly divides a single image into a plurality of images which are simultaneously projected onto a single sensor array. The optical assembly is arranged so that each of the plurality of images can be made to pass through a filter of a different type. For example a polarizing filter of a different orientation, or a filter which passes a different spectral band. In this way a single digital camera having a single chip sensor array can simultaneously receive multiple substantially identical images which have been acted on by different filters. This allows data capture from a single frame of a single camera to be used to perform stress analysis, or spectral analysis. This is particularly useful when high speed image capture is desired which contains stress or spectral data, because each frame captured from the sensor array contains multiple images which can be processed to obtain stress or spectral data.

Abstract: A method for generating polarized laser output radiation utilizes a laser resonator whose active medium exhibits thermally induced birefringence. The radiation fields oscillating in the laser resonator are not subjected to polarization selection, and only the radiation field exhibiting the desired polarization state (p) is partially output. Only a prescribed polarization of the radiation fields of the laser radiation which can oscillate in the resonator can be partially output from the resonator with a prescribed output level and all differently polarized radiation fields remain in the resonator in a completely reflecting fashion.

Abstract: A double-pass birefringent filter apparatus comprises an external-interface apparatus (illustratively including of a beam-displacer element and a waveplate element); a birefringent filter comprised of a series of several birefringent waveplates; and a wrap-around unit (illustratively comprised of a beam-displacer element and a retro-reflector). In response to an input beam received at the external-interface apparatus, the double-pass birefringent filter forms two output beams having complimentary intensities which vary periodically with frequency.

Abstract: An intracavity, frequency-doubled, external-cavity, optically-pumped semiconductor laser in accordance with the present invention includes a semiconductor multilayer surface-emitting gain-structure surmounting a Bragg mirror. An external concave mirror and the Bragg-mirror define a stable laser-resonator including the gain-structure. A birefringent filter is located in the resonator, inclined at an angle to the resonator axis, for selecting a fundamental frequency of the laser-radiation within a gain bandwidth characteristic of semiconductor structure. An optically-nonlinear crystal is located in the laser-resonator between the birefringent filter and the gain-structure and arranged to double the selected frequency of laser-radiation. The gain-structure is coated with a dichroic coating which reflects the frequency-doubled radiation and transmits the fundamental radiation and optical pump-light.

Abstract: A beam delivery system for a laser emitting at a relevant wavelength of less than 200 nm is provided. The system includes a sealed enclosure connected to the laser and surrounding the path of the beam as it exits the laser resonator. The enclosure extends between the laser output coupler and a photodetector sensitive at the wavelength of the relevant laser emission. The interior of the enclosure, and thus the beam path between the output coupler and the detector, is substantially free of species that strongly photoabsorb radiation at the relevant laser emission wavelength. A beam splitting element diverts at least a portion of the beam for measurement by the detector. The beam splitting element preferably includes a beam splitting mirror, holographic beam sampler or diffraction grating. In addition, optics are preferably provided for filtering a visible portion of the diverted beam, so that substantially only a VUV portion of the diverted beam is received at the detector.

Abstract: A laser system includes a travelling-wave active laser-resonator arranged for generating laser-radiation having a first wavelength and arranged such that the first-wavelength radiation circulates in only one direction therein. An optically-nonlinear element is positioned in the travelling-wave laser-resonator such that the first-wavelength radiation circulates therethrough. Radiation having a second-wavelength is injected into the optically-nonlinear crystal such that the first-wavelength radiation and second-wavelength radiation mix therein, thereby generating radiation having the sum-frequency of the first and second-wavelength radiations. The sum-frequency radiation from the optically-nonlinear element is delivered from the laser system as output-radiation. In one example, the travelling-wave resonator has a YVO4 gain medium generating radiation having a wavelength of about 1064 nm. The optically-nonlinear crystal is a CLBO crystal.

Abstract: A Q-switched neodymium laser may be operated in the 0.9 &mgr;m [( &lgr;1)] band at relatively high gain levels. The laser uses a birefringent filter which provides selective discrimination for wavelengths near 1 &mgr;m [(&lgr;2)] and prevents parasitic lasing in that wavelength region. The filter includes a specific wavelength dependent crystal quartz wave plate in combination with a linear polarizer. The linear polarizer is placed between two mirrors which define a laser cavity. The wave plate provides exactly 2 full waves of retardation at the desired wavelength &lgr;1 in the 0.9 &mgr;m band, and exactly 1.75 waves of retardation at wavelength &lgr;2 near the center of the 1 &mgr;m band for one pass. A Q-switching device such as a Pockels cell is positioned in the laser cavity to selectively control a pulsed emission at &lgr;1.

Abstract: A thermal birefringence compensator for a double pass laser system, which includes a polarization or conventionally outcoupled laser resonator, a gain medium and a compensator optically coupled to the gain medium. In one implementation, the compensator, which acts as an end reflector, includes a Benson prism, a first quarter waveplate with its principle axes aligned to the fold axis of the Benson prism, and a second quarter waveplate with its principle axes at 45° to the fold axis of the Benson prism. Alternatively, the compensation's prism can be a Porro prism.

Abstract: A solid state laser device made from a nonlinear optic quaternary alloy of Silver, Gallium, Selenium and Tellurium semiconductor material or Silver, Gallium, Sulfur and Tellurium semiconductor material. The Tellurium component in each alloy provides quaternary alloying anion modification of an underlying ternary semiconductor crystal and achieves tuning of the birefringence and tuning of the wavelength passband of the semiconductor material. The tuned quaternary alloy enables beam walkoff-free noncritical phase match operation of the laser device including use of a phase match angle supporting optimum use of the material's nonlinear properties, maximized useful length of the material crystal, room temperature wavelength changing operation, significantly increased second order nonlinear susceptibility, a factor of ten reduction in the walk-off angle and photon energy conversion efficiencies several times those usually achieved.

Abstract: In a resonating-type solid-state laser oscillator including a birefringent solid-state element containing a laser active medium and providing a plurality of thermal lenses during excitation and reflecting mirrors arranged oppositely to each other on both sides of the solid-state element so that their optical axes are coincident to each other, a prescribed relationship is given among the refractive index and length of the solid-state element, the radii of curvature of the reflection mirrors, the distances between the reflecting mirrors and the solid-state element and the difference between plural thermal lenses by refringence of the solid-state element so that oscillation areas due to the plurality of thermal lenses are separated from each other.

Abstract: An optical fiber polarization controller which has compact size by employing wave plates made of short sections of a first optical fiber having inherent birefringence such as a polarization maintaining optical fiber. In the control of the polarization state of input light, a second optical fiber, for example a single mode fiber, connected to the first optical fiber is twisted using fixing knobs, thereby rotating the birefringence axis of the first optical fiber with respect to the second optical fiber.

Abstract: Linearly-polarized, single-frequency fiber lasers are realized with optical fibers that have first and second refractive indices in a first fiber grating and third and fourth refractive indices in a second fiber grating. The first and third refractive indices are arranged along a first transverse fiber axis and the second and fourth refractive indices are arranged along a second transverse fiber axis. The grating periods and the first and third refractive indices are selected to generate spectrally-aligned signal reflectances along the first transverse axis and the grating periods and the second and fourth refractive indices are selected to generate spectrally-spaced signal reflectances along the second transverse axis. Thus, a fiber resonator is formed only along the first transverse axis and the fiber laser's output signal is linearly polarized.

Abstract: An intracavity, frequency-doubled, external-cavity, optically-pumped semiconductor laser in accordance with the present invention includes a monolithic surface-emitting semiconductor layer structure including a Bragg mirror portion and a gain portion. An external mirror and the Bragg-mirror portion define a laser resonant-cavity including the gain-portion of the semiconductor layer structure. A birefringent filter is located in the resonant-cavity for selecting a frequency of the laser-radiation within a gain bandwidth characteristic of semiconductor structure. An optically-nonlinear crystal is located in the resonant-cavity between the birefringent filter and the external mirror and arranged to double the selected frequency of laser-radiation.

Abstract: A laser system includes a light amplifier medium provided with an optical waveguide layer which controls the transverse mode to a fundamental transverse mode in one direction, a first resonator mirror optical system which is opposed to a first light outlet end face of the light amplifier medium and reflects a laser beam radiated from the first light outlet end face to impinge upon the first light outlet end face, and a second resonator mirror optical system which is opposed to a second light outlet end face of the light amplifier medium and reflects a laser beam radiated from the second light outlet end face to impinge upon the second light outlet end face.

Abstract: A compound planar waveguide comprising multiple confinement structures that provides independent containment of pump and laser radiation. The waveguide may be formed of multiple layers of laser-active and laser-inactive materials to provide step changes in refractive index. The planar waveguide may include a central laserable core layer substantially sandwiched by at least two non-laserable cladding layers to provide an interface between the inner surfaces of the cladding layers and the gain medium core to define a first waveguide by virtue of an index of refraction discontinuity for containing developed laser radiation, and wherein the outer surfaces of the cladding layers define a second waveguide by virtue of an index of refraction discontinuity for containing pump radiation within the waveguide. The second waveguide may be also defined by an interface formed between the cladding layers and additional non-laserable external layers which sandwich the cladding layers.

Abstract: External-cavity optically-pumped semiconductor lasers (OPS-lasers) including an OPS-structure having a mirror-structure surmounted by a surface-emitting, semiconductor multilayer (periodic) gain-structure are disclosed. The gain-structure is pumped by light from diode-lasers. The OPS-lasers can provide fundamental laser output-power of about two Watts (2.0 W) or greater. Intracavity frequency-converted arrangements of the OPS-lasers can provide harmonic laser output-power of about one-hundred milliwatts (100 mW) or greater, even at wavelengths in the ultraviolet region of the electromagnetic spectrum. These high output powers can be provided even in single axial-mode operation.

Abstract: Stable operation of an ultra-compact modelocked fiber laser generating short optical pulses generally without use of any non-fiber, intra-cavity polarization-manipulating elements is obtained by employing a saturable absorber coupled to one end of a highly-birefringent fiber serving as the laser cavity. Once the laser is modelocked in one of the polarization axes of the highly-birefringent fiber, the degeneracy of the polarization axis is eliminated and cw oscillation along the other polarization axis is also prevented. Without a polarization-dependent loss in the cavity, the modelocked polarization axis is indeterminate, i.e., modelocking can occur on either of the polarization axes. However, the introduction of only a small polarization dependent loss is sufficient to ensure the reliable start-up of modelocking on only the low-loss axis.

Abstract: A unidirectionally operating laser apparatus using a semi-monolithic ring cavity having a compact structure capable of achieving a high frequency stability and a high-speed laser frequency tuning and modulation. The laser apparatus includes a laser active medium having a curved surface exhibiting an anti-reflection characteristic for a pump laser beam from a pump laser incident thereon while exhibiting a high reflection characteristic for an oscillating laser beam, a planar surface exhibiting an anti-reflection characteristic for the oscillating laser beam, and an optically-active polarization rotator attached to one side portion of the planar surface. The laser apparatus also includes an output mirror separated from the laser active medium, the output mirror having a curved surface with a coating exhibiting a higher reflectance coefficient for S-polarized beams than that for P-polarized beams, and a piezo-electric transducer.

Abstract: A second harmonic generator comprising a semiconductor laser as an excitation light source and a resonator having a solid laser crystal excited by the excitation light source, a control element for controlling the wavelength of a first oscillation wave generated from the solid laser crystal and a nonlinear crystal for wavelength converting the first oscillation wave as a fundamental wave into a second harmonic wave as a second oscillation wave, wherein the components of the resonator are arranged in the order of a first laser mirror, solid laser crystal, wavelength control element, nonlinear crystal and second laser mirror from the input side of the excitation light.

Abstract: A solid state laser includes a resonator, a solid laser crystal disposed in the resonator, a pumping source for pumping the laser crystal, a pair of .lambda./4 plates which is disposed in the resonator with the laser crystal intervening therebetween and makes an oscillation beam of a twisted mode, and a polarization control element which is disposed in the resonator and sets the linear polarization of the solid state laser beam in a predetermined direction. The solid laser crystal is a birefringent crystal and an optical axis of the birefringence of the solid laser crystal is oriented in the direction of the linear polarization of the solid state laser beam set by the polarization control element.

Abstract: A semiconductor optical functional device is divided into two regions of a first region 1 and a second region 2 adjacent to each other in a longitudinal direction of a semiconductor optical waveguide. The first region 1 is provided with a region including an MQW structure in which a compressive strain is introduced, and the second region 2 is provided with a region including an MQW structure in which a tensile strain is introduced. Electrodes 3 and 4 formed separately and independently from each other are respectively disposed on the first region 1 and the second region 2, and bias voltages applied to the electrodes 3 and 4 are adjusted so that transmissivities for light having a TE mode component and light having a TM mode component are independently controlled.

Abstract: The present invention is a system and method for mode-locking a laser, comprising reversibly converting radiation in the laser at a fundamental frequency into radiation at a second harmonic frequency, discriminating the radiation at the fundamental frequency using a polarization of the radiation at the fundamental frequency, and reconverting the radiation at the second harmonic frequency into radiation at the fundamental frequency.