Abstract: A laser producing high energy ultrashort laser pulses comprises a normal dispersion segment, a gain segment, an anomalous dispersion segment with negligible nonlinearity and an effective saturable absorber arranged to form a laser cavity. Each segment is optically interconnected so that a laser pulse will propagate self-similarly therein. (A pulse that propagates in a self-similar manner is sometimes referred to as a “similariton.”) With this laser the limitations of prior art laser oscillators are avoided. Also provided are means for pumping the gain medium in the laser cavity, and means for extracting laser pulses from the laser cavity. The laser cavity is preferably a ring cavity. Preferably the laser is configured to achieve unidirectional circulation of laser pulses therein. This configuration is scalable to much higher pulse energy than lasers based on soliton-like pulse shaping.

Abstract: A four-port optical filter is provided including two tapered optical fibers, each having a loop in the area of their tapered portions, which are located relative to one another to form a ring resonator. The optical filter has a low Q with a broadband filter response which is useful as a channel interleaver or de-interleaver for dense wavelength division multiplexing and other applications.

Abstract: An optical microresonator includes microcylinder and spiral resonant waveguide formed on the microcylinder that optically couples light from an optical source waveguide to the microcylinder and slows light propagating along the microcylinder. A coupling element, for example, a diffraction grating can be operative with the resonant waveguide structure and configured to meet a desired phase matching A second microcylinder having a spiral resonant waveguide formed thereon can be positioned adjacent to the spiral resonant waveguide formed on the first microcylinder for coupling therewith. The spiral resonant waveguides on first and second microcylinders can be configured for slowing light propagating along the microcylinder.

Abstract: A CMOS processing compatible germanium on silicon integrated waveguide photodiode. Positioning contacts in predicted low optical field regions, establishing side trenches in the silicon layer along the length of the photodiode reduces optical losses. Novel taper dimensions are selected based on the desirability of expected operational modes, reducing optical losses when light is injected from the silicon layer to the germanium layer. Reduced vertical mismatch systems have improved coupling between waveguide and photodiode. Light is coupled into and/or out of a novel silicon ring resonator and integrated waveguide photodiode system with reduced optical losses by careful design of the geometry of the optical path. An integrated waveguide photodiode with a reflector enables transmitted light to reflect back through the integrated waveguide photodiode, improving sensitivity. Careful selection of the dimensions of a novel integrated waveguide microdisk photodiode system results in reduced scattering.

Abstract: An optical structure includes a substrate, a circular grating resonator (CGR) formed on the substrate, the CGR including a center disc and a plurality of concentric rings spaced from one another; an input planar waveguide and an output planar waveguide each formed on the substrate, the input planar waveguide and the output planar waveguide optically coupled to the CGR; and an electrode pair, formed on the substrate, coplanar with the input and output planar waveguides, the electrode pair comprising an electrically conductive material in contact with opposing ends of the center disc of the CGR so as to render the CGR capable of electro-optical control.

Abstract: A transverse closed-loop fiber resonator (10) includes an inner cladding (102) having a surface (300) peripherally forming a closed-loop shape for confining light to the surface (300). The inner cladding has a first diameter thickness (104) and a first index of refraction profile in a cross-sectional portion of the transverse closed-loop fiber resonator (10). A ringed-core (120) corresponding to the closed-loop shape is disposed on the corresponding surface of the inner cladding (102). The ringed-core (120) has a second thickness (124) of material thinner than the first diameter thickness (104), and a second index of refraction profile greater than the first index of the inner cladding by an index delta in the cross-sectional portion of the transverse closed-loop fiber resonator such that the ringed-core can guide light within the ringed-core traversely around the closed-loop shape.

Abstract: A laser-induced optical wiring apparatus is provided wherein optical wiring is realized by digital operations of a laser oscillator. The apparatus includes optical ring resonator formed of a loop-shaped optical waveguide on substrate. At least two optical gain sections are provided on the optical ring resonator. When each optical gain section is activated, a laser oscillator including the optical ring resonator and optical gain sections is enabled to oscillate. In this state, the gain of at least one of the optical gain sections is changed in accordance with an input signal, thereby changing the optical route gain of the optical ring resonator to change the oscillation state of the laser oscillator. A change in the laser oscillation state is detected by the optical gain section other than the at least one optical gain section, whereby an output signal is acquired.

Abstract: A vertical cavity surface-emitting laser (VCSEL) and a method of fabricating the same with easier alignment of a light output side aperture and an oxide aperture, The VCSEL includes: lower and upper reflection layers laminated with each other and forming a longitudinal resonance section there between; an active layer for producing a laser beam, an electrode formed in a ring shape on the upper reflection layer so the electrode has an aperture through which the laser beam is projected; a contact layer formed on the upper reflection layer; a ¼ wavelength layer formed on the contact layer such that a high transmittance area with the highest transmittance for the laser beam is formed within the aperture of the electrode; and a dielectric layer covering the contact layer and the ¼ wavelength layer, except for the electrode formed part.

Abstract: An external resonator which includes a multiple resonator with parameters which allow stable wavelength control, and a variable-wavelength light source includes such an external resonator are provided. The external resonator is a multiple resonator which is made up of first to third ring-shaped resonators, each having different light path length, and connected in series via optical coupling means. The parameters of the multiple resonator are characterized in that all the following Expressions <1>, <2> and <3> hold: L1={M1/(M1?1)}L0 <1> L2={M2/(M2?1)}L0 <2> M2?1=(M1?1)2 <3> where L0 is the light path length of the first resonator, L1 is the light path length of the second resonator and L2 is the light path length of the third resonator, and M1 and M2 are integers of 3 or greater.

Abstract: A widely-tunable laser apparatus comprises a plurality of tunable lasers having different ranges that overlap to encompass a desired operating range of wavelengths (for example from 1250 nm to 1650 nm) of the widely-tunable laser apparatus. The tunable lasers are tunable synchronously and selectively with their respective outputs connected in common to sweep the output of the widely-tunable laser apparatus substantially continuously over said operating range. The tunable lasers share the same tuning means which has a plurality of independent channels, each for light from a respective one of the tunable lasers.

Abstract: A narrow-band laser device for exposure apparatus that allows to reduce damage to, and to hence extend the life of, optical elements such as chamber windows, output coupling mirrors or the like. A ring resonator is provided in an amplification stage laser of the narrow-band laser device for exposure apparatus that comprises an oscillation stage laser and an amplification stage laser. An OC, a high reflection mirror and a high reflection mirror are arranged to be offset, for instance, relative to a longitudinal direction axis of discharge electrodes. As a result, the beam width of laser light injected through the OC of the amplification stage laser becomes wider as the beam shifts inside the ring resonator, in each round trip within the ring resonator. The energy density of laser light in the optical elements of the amplification stage laser becomes reduced thereby, thus prolonging the life of the optical elements.

Abstract: An optical structure comprising an optical resonator is provided. The optical resonator comprises a first set of nested closed optical regions, forming a distributed feedback resonator structure with a direction of radially alternating optical refractive index, and a second set of nested optical regions, forming a distributed feedback resonator structure with a direction of radially alternating optical refractive index. Each optical region of the second set is interrupted by a first gap region with a lower refractive index, wherein the first gap regions substantially overlap in the direction of radially alternating optical refractive index. The first set is arranged nested within the second set and the optical structure further comprises a first optical waveguide optically coupled to the optical resonator via a first waveguide portion reaching into the first gap regions and being arranged coplanar to the optical resonator.

Abstract: A tunable lasing device (100) comprising a ring-shaped laser cavity (102), an optical gain element (104), a bi-directional output coupler (106) and a frequency selection means (114). The frequency selection means is generally a grating with a refractive index that determines a grating reflection frequency. Single mode laser operation is achieved where a cavity mode frequency of the ring-shaped laser cavity coincides with a grating reflection frequency. The refractive index of the grating can be modified by the injection of a variable current. In this way, the lasing frequency can be rapidly tuned between cavity mode frequencies.

Abstract: Providing a high peak power short pulse duration gas discharge laser output pulse comprises a pulse stretcher a laser output pulse optical delay initiating optic diverting a portion of the output laser pulse into an optical delay having an optical delay path and comprising a plurality of confocal resonators in series aligned to deliver an output of the optical delay to the laser output pulse optical delay initiating optic. The plurality of confocal resonators comprises four confocal resonators comprising a twelve pass four mirror arrangement. An apparatus and method may comprise a plurality, e.g., two pulse stretchers in series and may include spatial coherency metrology.

Abstract: A coupled resonator includes a plurality of resonators such that at least one of the resonators is modified so as to adjust the resonant frequency associated with the coupled resonator.

Abstract: A microphotonic light source includes an optical pump and a plurality of waveguides that distribute optical pump power of the optical pump. At least one Erbium-doped laser ring is coupled to at least one of the waveguides so as to match the resonance condition of the optical pump.

Abstract: The invention concerns solid-state gyrolasers used to measure rotation speeds or relative angular positions. This type of equipment is used, in particular, in aeronautical applications. The purpose of the invention is to complete the optic devices required to control the instability of lasers, using specific optic devices that eliminate the blind region. In this way, a “fully optic” solid-state laser is obtained, without moving parts, stable, and without blind regions. These devices comprise in particular reciprocal and nonreciprocal optical rotators, arranged so that two counter-propagating optical modes travel in the cavity at sufficiently different frequencies to avoid mode locking.

Abstract: The present invention relates to a laser including a laser amplifier and a laser resonator. The laser amplifier includes a disk-shaped active medium having a reflector. The active medium rests on a cooling means for cooling said active medium and said reflector. The reflector embodies a mirror of said laser resonator. The laser amplifier includes an optical means for refocusing a pumping light configured for repeatedly deviating said pumping light and refocusing said pumping light onto the active medium for causing a multiple passage of said pumping light through said active medium. Such a thin-disk laser is not prone to thermal lensing. According to the invention, the laser resonator is formed as a ring resonator. Two optical waves can travel around within the ring resonator in different directions. An optical selection means is provided for giving preference to propagation of one of the both optical waves traveling around that can be coupled out as an output laser beam.

Abstract: A laser oscillator is provided that makes it possible to stably obtain a laser beam output in continuous or pulsed oscillation that has an intensity distribution of a top-hat profile or a fundamental transverse mode profile. An optical resonator is used that maintains the polarization of a laser beam traveling in the resonator but rotates the transverse mode pattern thereof. The resonator can be a ring resonator that includes an image rotating element, a nonplanar ring resonator, a diagonally crossed right-angle prism resonator or other such resonator. A combination of a polarizer, and a half-wave plate or Faraday rotator is used to preserve the polarization in the resonator. The optical path of the laser resonator can be intersected with another resonator of a conventional Fabry-Perot or planar ring resonator, and the optical paths coupled, using a beam-splitter or polarizer.

Abstract: A laser system, such as a master oscillator/power amplifier system, comprises a gain medium and a stimulated Brillouin scattering SBS mirror system. The SBS mirror system includes an in situ filtered SBS medium that comprises a compound having a small negative non-linear index of refraction, such as a perfluoro compound. An SBS relay telescope having a telescope focal point includes a baffle at the telescope focal point which blocks off angle beams. A beam splitter is placed between the SBS mirror system and the SBS relay telescope, directing a fraction of the beam to an alternate beam path for an alignment fiducial. The SBS mirror system has a collimated SBS cell and a focused SBS cell. An adjustable attenuator is placed between the collimated SBS cell and the focused SBS cell, by which pulse width of the reflected beam can be adjusted.

Abstract: An apparatus and method is provided for facilitating ionization of a gas medium of a laser gyroscope. The apparatus and method employ a solid state light emitting device as a start aid for the laser gyroscope. The solid state light emitting device has a wavelength at or below a threshold wavelength based on a work function of a cathode coating material to prompt ionization of a gas medium within the laser gyroscope.

Abstract: A near-field light source device including a semiconductor laser comprised of laminated semiconductor layers and having a ring-type optical resonator with a plurality of wave guides connected via mirror portions, a light blocking film formed in one of the mirror portions and having a small opening not greater than a wavelength size, and a diffraction grating formed on the light blocking film. The light oscillated from the semiconductor laser is diffracted by the diffraction grating, the diffracted light is coupled to a rotation mode in the ring-type optical resonator, and near-field light is generated via the small opening.

Abstract: A single-frequency Brillouin fiber ring laser with extremely narrow linewidth comprises a single-frequency narrow-linewidth rapid-tunable pump laser, a temperature-controlled acoustically-damped package for Brillouin fiber ring laser cavity, and an auto-tracking feedback electronic loop with novel configuration for active stabilization. The Pound-Drever-Hall frequency-locking technique is employed to keep pump laser frequency in resonance with one of the Brillouin fiber ring cavity modes. Instead of changing cavity length of Brillouin fiber ring laser, the pump laser frequency is rapidly tuned in the auto-tracking feedback electronic loop. This enables extremely narrow linewidth radiation emitted from a Brillouin fiber ring laser without stretching the fiber ring.

Abstract: An optically pumped semiconductor laser includes an active ring-resonator having two or more optically pumped semiconductor (OPS) structures each including a mirror-structure and a multilayer gain-structure. The mirror-structures serve as fold mirrors for the resonator axis. An optically nonlinear crystal may be included in the ring-resonator for generating second-harmonic radiation from fundamental radiation generated in the resonator. Another optically nonlinear crystal may be provided for generating third-harmonic or fourth-harmonic radiation from the second-harmonic radiation. In one example, including a third-harmonic generating crystal, a passive ring-resonator partially coaxial with the active ring-resonator is provided for circulating second-harmonic radiation to provide resonant amplification of the second-harmonic radiation for enhancing third-harmonic conversion.

Abstract: A photonic-crystal fiber provides dispersion compensation in a soliton fiber laser. The anomalous dispersion provided by the photonic-crystal fiber permits construction of a femtosecond fiber laser at 1 ?m wavelength without prisms or diffraction gratings. The laser produces ˜100-fs pulses with 1 nJ energy, and is a major step toward environmentally-stable all-fiber devices at 1 ?m.

Abstract: A widely-tunable laser apparatus comprises a plurality of tunable lasers having different ranges that overlap to encompass a desired operating range of wavelengths (for example from 1250 nm to 1650 nm) of the widely-tunable laser apparatus. The tunable lasers are tunable synchronously and selectively with their respective outputs connected in common to sweep the output of the widely-tunable laser apparatus substantially continuously over said operating range. The tunable lasers share the same tuning means which has a plurality of independent channels, each for light from a respective one of the tunable lasers.

Abstract: The invention concerns solid-state gyrolasers used to measure rotation speeds or relative angular positions. This type of equipment is used, in particular, in aeronautical applications. The purpose of the invention is to complete the optic devices required to control the instability of ring-shaped solid-state lasers using specific optic devices that eliminate the blind region without adding a measurement bias. In this way, a “fully optic” solid-state laser is obtained, without moving parts, stable, and without blind region. These devices comprise in particular polarization separation optical devices, reciprocal and nonreciprocal optical rotators arranged so that four linearly polarized optical modes travel in the cavity at sufficiently different frequencies to avoid mode locking.

Abstract: A Master Oscillator (MO)—Power Amplifier (PA) configuration (MOPA) can be used advantageously in an excimer laser system for micro-lithography applications, where semiconductor manufacturers demand powers of 40 W or more in order to support the throughput requirements of advanced lithography scanner systems. A MOPA-based laser system can provide both high pulse energies and high spectral purity. A MOPA system can utilize a multi-pass PA, as well as a special beam path capable of reducing the amount of ASE (Amplified Spontaneous Emission) and feedback to the MO. Lithography scanner optics are primarily fused silica, such that the peak pulse power must be kept low to avoid material compaction when a MOPA system is used with lithography applications. This conflict between the demand for high average power and the low peak power requirement of the pulsed excimer laser source can be resolved by using a novel beam path to generate a sufficiently long pulse length.

Abstract: A coupled waveguide optical microresonator is formed from a plurality of microcylinders coupled together. Each microcylinder includes a resonant waveguide. At least one of the microcylinders is adapted to be positioned adjacent an optical source waveguide for optically coupling light from an optical source waveguide onto the resonant waveguide on the microcylinder. The microcylinders are coupled together at the resonant waveguides, which are mutually coupled. Any coupled fields add coherently with each other.

Abstract: A vertically-coupled whispering gallery mode (WGM) resonator optical waveguide, a method of reducing a group velocity of light, and a method of making a waveguide are provided. The vertically-coupled WGM waveguide comprises a cylindrical rod portion having a round cross-section and an outer surface. First and second ring-shaped resonators are formed on the outer surface of the cylindrical rod portion and are spaced from each other along a longitudinal direction of the cylindrical rod. The first and second ring-shaped resonators are capable of being coupled to each other by way an evanescent field formed in an interior of the cylindrical rod portion.

Abstract: This application describes use of an opto-electronic feedback in oscillators to suppress phase noise based on the high Q factor of the opto-electronic feedback.

Abstract: A resonator structure is presented comprising a closed loop resonator having a distributed Bragg reflector for confining the light within the guiding core. In one embodiment the light is confined from both the internal and the external sides of the device forming a guiding channel (defect) or just by the external side forming a disk resonator. Although the perfectly circular shape is generally preferred, the resonator could be of any closed loop shape such as an ellipse, etc. Although not mentioned explicitly throughout the text, the Bragg reflectors can of any type of distributed reflector such as, for example, a photonic bandgap crystal where the Bragg reflector is constructed by series of holes in a dielectric material. The resonator structure can be used in various applications, such as optical filters, lasers, modulators, spectrum analyzers, wavelockers, interleave filters, and optical add drop multiplexers.

Abstract: A rugged resonator for a laser includes a laser pump housing. An X-fold resonator assembly is configured to receive and hold the laser pump housing. The resonator includes at least four mirrors, a first, a second, a third, and a fourth mirror. The first mirror is configured to receive a first incident laser beam from the first end and to reflect a first reflected beam to reflect as a third reflected beam from the third mirror. The second mirror is configured to receive a second incident laser beam from the second end and reflecting a second reflected beam to intersect the first reflected beam and to reflect as a fourth reflected beam from the fourth mirror. An optical coupler is affixed to an optics plate and configured to receive the third reflected beam. A high reflector is affixed to the optics plate and configured to receive the fourth reflected beam.

Abstract: A Raman ring resonator based laser and wavelength converter method and apparatus. In one aspect of the present invention, the disclosed method includes directing a first optical beam of a first wavelength and a first power level into a first ring resonator defined in a semiconductor material. Emission of a second optical beam of a second wavelength is caused in the first ring resonator by propagating the first optical beam around the first ring resonator. The first power level is sufficient to cause the emission of the second optical beam. The first optical beam is directed out of the first ring resonator after a round trip of the first optical beam around the first ring resonator. The second optical beam is recirculated around the first ring resonator to further stimulate the emission of the second optical beam in the first ring resonator.

Abstract: A locally-outcoupled optical resonator has whispering gallery modes existing in a nearly circular resonator. Light is outcoupled by providing a local perturbing feature on the perimeter of the locally-outcoupled cavity resonator. The perturbing feature provides an outcoupling or loss mechanism that asymmetrically interacts with circulating whispering gallery modes, thereby making the resonator capable of uni-directional output.

Abstract: An optically-pumped mode-locked fiber ring laser for optical clock recovery of multiple wavelength division multiplexed optical signals actively mode-locks a plurality of outputs of the laser as a plurality of recovered clocks for a plurality of the multiple wavelength division multiplexed optical signals.

Abstract: The invention provides a system for generating X-rays via the process of inverse Compton scattering. The system includes a high repetition rate laser adapted to direct high-energy optical pulses in a first direction in a laser cavity and a source of pulsed electron beam adapted to direct electron beam in a second direction opposite to the first direction in the laser cavity. The electron beam interacts with photons in the optical pulses in the laser cavity to produce X-rays in the second direction.

Abstract: In a device for reducing the peak power of a pulsed laser light source, in particular for a projection exposure system, there is arranged in the beam path (1) at least one beam splitter apparatus (3, 4) by means of which a detour line (5 or 11) is produced, via reflecting components (6, 7, 8 or 12, 13, 14) for at least one partial beam (1b) with subsequent recombination at a beam recombining element (9 or 15) with the other partial beam or beams (1b or 10b) to form a total beam.

Abstract: The present invention relates to a millimeter wave frequency band optical oscillator used for an oscillating frequency signal source of millimeter waves transmitted from a repeater to a wireless subscriber in a millimeter wave wireless subscriber communication system for a next-generation (i.e., 5th generation or less) very high speed wireless internet service, wherein a loop mirror and a pair of optical fiber grating mirrors are used. A wavelength fixed type and a wavelength tunable type optical fiber grating mirrors are connected in a serial manner to constitute a dual laser mode resonator capable of simultaneously oscillating two laser modes, which are appropriate to each wavelength. Therefore, it is possible to obtain a laser light source capable of an extremely high frequency (60 GHz or more) modulation by using beat phenomena between two laser modes.

Abstract: By substituting a ring optical parametric oscillator for the linear cavity, one eliminates the effects of feedback solved in the prior art by the use of isolators and by the purposeful off-axis alignment of the pump laser beam. The result is an exceedingly robust system with state-of-the-art efficiency for maximizing output power while preserving beam quality.

Abstract: External cavity, widely tunable lasers and methods of tuning the same are disclosed. One such example laser includes a semiconductor laser, a ring resonator coupled to the semiconductor laser; and a Bragg grating. The Bragg grating is coupled to the ring resonator to reflect a portion of light output by the ring resonator back to the semiconductor laser to select a lasing frequency of the semiconductor laser.

Abstract: A tunable semiconductor laser device is presented. The device comprises a laser structure formed by at least two waveguides and an active region located within at least a segment of one of the waveguides; and comprises a tunable spectral filter optically coupled to the laser structure. The tunable spectral filter includes at least two filtering elements, at least one of them being a microring cavity.

Abstract: A fiber-based ring cavity tunable laser is disclosed in this invention that has full range high speed tuning achieved by combining a optical tunable filter with a period comb-shaped filter with central wavelengths anchored on International Telecommunication Union (ITU) grids. By using segments of dispersion managed fibers with predefined segment lengths the group delay differences are also reduced. The temperature sensitivity of optical transmission is also reduced by arranging the longitudinal axis of different segments of the optical fibers to orient with a relative angular difference, e.g., with an angular difference of ninety degrees.

Abstract: A non-monolithic ring laser cavity comprising: (a) a gain medium (1); (b) a first polarization rotation element arranged to rotate the polarization of light propagating in the cavity with a predetermined handedness irrespective of the direction of propagation of the light; (c) a second polarization rotation element (7) arranged-to rotate the polarization of light propagating in the cavity with a handedness which is dependent upon the direction of propagation of the light; (d) a polarization selection element (5, 6) arranged to cause loss to light propagating in the cavity, the loss being determined by the polarization of light incident upon the polarization selection element; wherein the polarization selection element comprises at least one mirror spaced away from the gain medium (1) and arranged to reflect light at an angle displaced from the normal such that the reflectivity of the at least one mirror is sufficiently polarization dependent that the laser oscillates uni-directionally.

Abstract: There is provided a millimeter wave band frequency optical oscillator predicted to be used as a millimeter wave oscillating frequency signal source in a base station of a millimeter wave wireless transmission system. The optical oscillator has a double resonator structure in which a pair of wavelength tunable fiber grating mirrors are inserted into a unilateral fiber-ring laser resonator in order to internally and additionally form a linear laser resonator. The double resonator structure composed of the two stable laser resonators can oscillate laser of two modes. Due to a beat phenomenon occurring between the two modes, received laser is modulated to an ultra-speed frequency of 60 GHz or greater. A variation in the gain within a resonator is induced by a polarization controller using the dependency of laser modes upon polarization. A modulation frequency is consecutively changed from 60 GHz to 80 GHz by controlling the wavelength of light reflected by the fiber grating mirrors.

Abstract: A diffractive optical element is interposed between the exit beams from a ring laser gyro readout and the photodetectors for detecting such beams. The diffractive optical element permits the use of photodetectors much reduced in size in order to minimize gyro performance degradation due to radiation.

Abstract: A scatterometer utilizes the dead zone resulting from lockup caused by scatter from a sample located in the optical path of a ring laser at a location where counter-rotating pulses cross. The frequency of one pulse relative to the other is varied across the lockup dead zone.

Abstract: The present invention relating to a device and method for multiplication of repetition frequency in optical pulse trains. The device and the method multiply repetition frequency of optical pulse train generated with ML-FRL with high stability. The device comprises an optical fiber ring composed of optical fibers, an optical amplifier and a modulator for optically modulating, and an electric signal generator generating high frequency signals. The device generates an optical pulse train of repeating frequency of fm, when applying electric signals of frequency of fm to the modulator. In addition to the construction, the stabilized optical pulse generator comprises a filter passing through frequencies of integer multiple of the applied modulation frequency fm, and a composite cavity composed of a plurality of optical fibers of which lengths are different each other.

Abstract: A broadband laser source comprising: a resonant cavity (1) containing a medium (2) which emits optical energy (3) in a continuum of wavelengths in response to application of pump energy (4) to the medium (2); a source of pump energy (5) for producing said optical energy (3); a frequency shifter (6) within the resonant cavity (1); and a tuneable spectral filter (7) within the resonant cavity (1), and the apparatus being such that in use the tuneable spectral filter (7) has a peak wavelength which is repeatedly swept in a substantially resonant fashion over a wavelength range equal to, or a fraction of, a linewidth of the broadband source such that the rate of change of the peak wavelength of the tuneable spectral filter (7) is substantially equal to the rate of change of the frequency of the optical energy (3) as it is frequency shifted within the resonant cavity (1) by the frequency shifter (6).

Abstract: A diode pumped optical parametric oscillator is disclosed. The apparatus includes a MOPA laser positioned to pump a photorefractive BaTiO3 crystal placed within a ring resonator formed by four mirrors. The interaction of the MOPA laser light incident on the BaTiO3 crystal and with the light reflected within the cavity efficiently converts the MOPA pump beam to a single frequency beam of high beam quality. Once the pump beam exceeds a threshold power level, it interacts with a nonlinear periodically poled lithium niobate crystal received within the ring cavity. The lithium niobate crystal efficiently converts the pump beam to signal and idler beams of different wavelengths, providing an efficient, tunable laser.