Abstract: A laser system includes an optical path having an intracavity relay telescope with a telescope focal point for imaging an output of the gain medium between an image location at or near the gain medium and an image location at or near an output coupler for the laser system. A kinematic mount is provided within a vacuum chamber, and adapted to secure beam baffles near the telescope focal point. An access port on the vacuum chamber is adapted for allowing insertion and removal of the beam baffles. A first baffle formed using an alignment pinhole aperture is used during alignment of the laser system. A second tapered baffle replaces the alignment aperture during operation and acts as a far-field baffle in which off angle beams strike the baffle a grazing angle of incidence, reducing fluence levels at the impact areas.

Abstract: A number of nonlinear optical fibers are configured in a parallel configuration. The fibers are pumped with optical pumps having a wavelength slightly longer than the zero dispersion wavelength for each fiber. By a demultiplexer optical signals within a certain wavelength interval are admitted to enter and exit the different fibers, in which parametric amplification can be achieved. By selecting the pump wavelength outside each corresponding interval crosstalk will be suppressed. The nonlinear fibers can be pumped by separate laser pumps, or two or more of the nonlinear fibers can be pumped by a common pump, depending on the different fiber properties. By tailoring fiber properties such as the zero dispersion wavelength, the second order dispersion coefficient and the fourth order dispersion coefficient, beneficial amplification characteristics can be achieved in different wavelength intervals.

Abstract: An improved gain-clamped optical amplifier is disclosed. A series of laser cavities are placed along the amplifier axis. The laser cavities are designed such that the carrier densities of the amplifier decline toward the signal output end. Since the gain clamping amplitudes at positions along the amplifier can be different, we have the freedom to optimize the optical gain at all location, to minimize the noise impact at the signal input end, and to maximize the saturation output power at the signal output end. In addition, carrier levering effect realized by gain/loss wings further lowers the noise figure, and extends the optical gain and saturation output power. An ideal optical amplifier with high linear gain, small noise figure, and large saturation output power and extended dynamic range is then achieved. Energy saving is the bonus of using the invented amplifiers.

Abstract: This application describes examples and implementations of optical devices and techniques based on use of whispering gallery mode (WGM) optical resonators that have nonlinear optical materials in multiple sectors where nonlinear coefficients of two adjacent sectors are oppositely poled.

Abstract: Tomographic methods and device for obtaining images of microscopic specimens such as Pap smears.

Abstract: A modulator having a waveguide and a microdisk resonator is disclosed. The waveguide has an input port for receiving a light signal of wavelength ? and an output port for transmitting modulated light. The microdisk resonator has a resonance at ? and is coupled to the waveguide between the input and output ports such that at least 10 percent of the light traveling in the waveguide is coupled to the microdisk resonator. The microdisk resonator further includes a material having a first state and a second state, the material absorbing more of the light in the first state than in the second state. The first and second states are selectable by a signal that is applied to the microdisk resonator. In one embodiment, the waveguide and the microdisk resonator occupy different portions of a sheet of material having the various layers used to construct the resonator.

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: An airgap type etalon has a higher degree of design freedom of a wavelength-temperature characteristic so that such a wavelength-temperature characteristic can be freely adjusted. The airgap type etalon includes a fixing block having one flat surface, and a transparent parallel flat plate having parallel flat surfaces formed with an antireflection coating and a reflection augmenting coating thereon, respectively. The flat surface at the antireflection coating side is joined to the flat surface of the fixing block. A parallel flat spacer has a thickness greater than that of the transparent parallel flat plate and an expansion coefficient different from that of the transparent parallel flat plate. One of the flat surfaces of the parallel flat spacer is joined to the flat surface of the fixing block. A transparent flat plate has opposite flat surfaces formed with an antireflection coating and a reflection augmenting coating thereon, respectively.

Abstract: An optical micro-electromechanical device includes a substrate and a mirror assembly suspended above the substrate. The mirror assembly includes a torsional beam and a cantilever. The cantilever includes a cantilever first end and a cantilever second end. The cantilever first end is attached to the torsional beam. The cantilever second end supports a mirror head. A connector is attached to the torsional beam. A counterweight is attached to the connector.

Abstract: A PLC type optical amplifier is provided. In the PLC type optical amplifier, an amplification layer is formed of a light amplifying material on a semiconductor substrate at a side of a core layer, spaced from the core layer. The amplification layer forms an annular light path. Thus, optical signals are coupled between the core layer and the amplification layer.

Abstract: A first pump pulse and a signal pulse are injected into a first optical parametric amplifier. This produces a first amplified signal pulse. At least one additional pump pulse and the first amplified signal pulse are injected into at least one additional optical parametric amplifier producing an increased power coherent optical pulse.

Abstract: The wavelength tunable optical filter (1) comprises a resonant cavity (4) delimited by two opposite reflective elements (8, 8′) which are not wavelength selective, and a reflector (7) external to the cavity (4). The external reflector (7) exhibits transmission peaks for an integer number N of optical frequencies and the Fabry-Perot cavity (4) delimiting a phase tuning section (11) is sized so that the distance between the optical frequencies of any two resonant modes of the cavity (4) is never equal to the difference between the optical frequencies of any two transmission peaks of the external reflector (7).

Abstract: A system for coherent simultaneous amplification of a broad spectral range of light that includes an optical parametric amplifier and a source of a seed pulse is described. A first angular dispersive element is operatively connected to the source of a seed pulse. A first imaging telescope is operatively connected to the first angular dispersive element and operatively connected to the optical parametric amplifier. A source of a pump pulse is operatively connected to the optical parametric amplifier. A second imaging telescope is operatively connected to the optical parametric amplifier and a second angular dispersive element is operatively connected to the second imaging telescope.

Abstract: A method and apparatus for enhancing the energy of THz radiation in the form of photon pulses comprising synchronously reflecting photon pulses using at least one pair of facing optical mirrors such that the reflected photon pulses encounter an electron bunch or another photon pulse travelling in the same direction and energy is transmitted from the electron bunch or the other photon pulse resulting in an increase in the energy of the reflected photon pulse.

Abstract: In a diode-pumped laser amplifier the inventive object is to increase the tolerance of the amplifier arrangement relative to variations of the input parameters significantly, so that fine-tuning is no longer necessary for guaranteeing the stability of the amplifier. Into a laser-active solid-state medium where a thermal lens of a strength which is different in orthogonal planes is generated in consequence of the irradiated pump radiation, a laser beam to be amplified is directed into the laser-active solid-state medium while being focused in the plane with a strong thermal lens, wherein a beam waist that is being generated lies in the area of the thermal lens. The laser amplifier can be used for amplifying the radiation of an oscillator.

Abstract: An optical amplifier arrangement, including an amplifying medium, which exhibits an approximately rectangular cross section with a long edge and a short edge, as well as at least two highly reflecting mirrors, between which the amplifying medium is disposed, whereby the long or the short edge of the cross section is along the X axis or the Y axis; the Z axis is the optical axis; and the X, Y and Z axis form a rectangular coordinate system. The mirrors are designed and arranged in such a manner that one beam, which is to be amplified and beamed in by an oscillator, passes repeatedly through the amplifying medium in the XZ plane and is amplified; and the size of the beam to be amplified in the X direction becomes larger after each passage.

Abstract: The present invention aims at providing a multi-wavelength light source for stably generating a plurality of oscillated lights of arbitrary wavelengths by a simplified constitution. To this end, the multi-wavelength light source of the present invention is provided with an acousto-optic tunable filter (AOTF) on an optical path of a resonator including an optical amplifier, so that the AOTF selects lights of plural wavelengths from input lights corresponding to multiple surface acoustic waves at different frequencies, respectively, and shifts the frequencies of the selected lights to output the frequency shifted lights to the optical path, thereby realizing the stable multi-wavelength oscillation of lights being propagated within the resonator.

Abstract: A waveguide for amplifying electromagnetic radiation of a characteristic wavelength includes a first reflector, a second reflector, and a gain medium having a characteristic wavelength of emission disposed between the first and second reflectors. The first and second reflectors are spaced apart from each other to form a microcavity which is off-resonance with respect to the characteristic wavelength of light emitted by the excited gain medium.

Abstract: A semiconductor structure includes a first cladding layer, a second cladding layer, and one or more semiconductor active regions. An optical resonator is formed by the inclusion of a first mirror and a second mirror at opposite ends of the structure with respect to the optical axis. One or more angled facets provide the semiconductor structure with optical coupling. The associated beam path along an optical axis within the structure is a zigzag path, which is substantially independent of the height of the active region. A signal generator and an optical amplifier may be formed with the structure. An optical modulator, multiplexer, and demultiplexer may also use the structure.

Abstract: The present invention aims at providing a multi-wavelength light source for stably generating a plurality of oscillated lights of arbitrary wavelengths by a simplified constitution. To this end, the multi-wavelength light source of the present invention is provided with an acousto-optic tunable filter (AOTF) on an optical path of a resonator including an optical amplifier, so that the AOTF selects lights of plural wavelengths from input lights corresponding to multiple surface acoustic waves at different frequencies, respectively, and shifts the frequencies of the selected lights to output the frequency shifted lights to the optical path, thereby realizing the stable multi-wavelength oscillation of lights being propagated within the resonator.

Abstract: In order to enable adjustment of the output wavelength of a laser, there is provided a laser comprising a laser-active material (100), which is excitable at not less than two laser wavelengths to emit laser beams with a gain, said gain being different at the two laser wavelengths, a resonator comprising two end mirrors (102, 110; 130, 132), in which resonator the laser-active material (100) is arranged and which resonator is adapted, with respect to its resonance conditions, to the laser wavelength having the lower gain, wherein one of said end mirrors (110, 132) is partially transmissive for radiation at said laser wavelengths, an output mirror (116), which is partially transmissive for said laser wavelengths and is arranged following the partially transmissive end mirror (110, 132) in the optical path, an optical element (112, 120), which is arranged between the partially transmissive end mirror (110, 132) and the output mirror (116), on which radiation is incident at said laser wavelengths and which has an

Abstract: An optical resonator receives a light beam having a first state of polarization. The resonator comprises a polarization modifying device (40) and a polarization dependent coupling device (30) for coupling light having the first state of polarization into a first path and for coupling light having a state of polarization perpendicular to the first state of polarization into a second path. The polarization dependent coupling device (30) is arranged to receive from a first propagation direction the light beam having the first state of polarization and to couple the light beam from the first propagation direction in the first path to the polarization modifying device (40). The polarization modifying device (40) is arranged for modifying the state of polarization of the light beam before reentering the first path of the polarization dependent coupling device (30) from a second propagation direction in order to couple into the second path a portion of the light beam traveling into the second propagation direction.

Abstract: An optical window signal generator which begins generation of an optical output signal in response to an optical activation pulse, and terminates generation of the optical output signal in response to an optical deactivation pulse. The rise time of the optical output signal is equal to the rise time of the optical activation pulse, and its fall time is equal to the rise time of the optical deactivation pulse.

Abstract: An integrated optical circuit device includes: a first optical element section including first and second element regions deposited along a thickness direction; a second optical element section formed away from the first optical element section, and a multimode interference region provided between the first and second optical element sections, the multimode interference region including a buried portion formed along a light propagation direction. The first and second optical element sections are optically coupled to each other via the multimode interference region.

Abstract: The invention is a double chirped mirror and a method of constructing a double chirped mirror for a frequency range of electromagnetic radiation, comprising specifying a design including a plurality of layers, the plurality of layers being transparent to the electromagnetic radiation and having refractive indices which vary between layers in the plurality of layers, and wherein for a first set of layers the optical thickness of alternate layers in the set of layers varies monotonically and the total optical thickness of a layer and the two adjacent half layers in the set of layers varies monotonically. The design is optimized by adjusting the optical thickness of layers in the plurality of layers.

Abstract: A monochromatic continuous light emitted from a laser source is introduced into an optical resonator, and resonated and amplified between reflecting mirrors provided in the optical resonator. An optoacoustic element controller applies a pulsed high frequency electric signal to an optoacoustic element so that the amplified monochromatic continuous light is pulsed through the optoacoustic element. The thus obtained pulsed light is diffracted in an oblique direction and taken out of the optical resonator to the outside.

Abstract: Optical pumping arrangements are provided for the broadband or multiple wavelength pumping of optical sources. Sources may be based on Raman gain media and may use multiple output couplers to couple out different wavelength ranges. Cascaded Raman resonator (CRR) configurations may also be used. Overlapping resonators at different wavelengths may be configured to share gain media, and may have separate portions in separate optical paths. Attenuation filters may also be used that are matched to the gain profile of a gain medium, to flatten the gain spectrum and allow equalization of gain to different output wavelengths. In one embodiment, polarization maintaining fiber is used to develop resonant conditions at different wavelengths in different polarization states. Wideband output gratings may be substituted for narrowband gratings to provide CRR configurations with a broader output band. Broadband amplification may also be provided by using a laser source operating in coherence collapse.

Abstract: The present invention provides optical systems and methods that use a plurality of optical reflectors to fold the optical path of an optical beam used in the optical system. By folding the optical path of the optical beam, the optical system and method of the present invention can in one instance minimize the over-all volume and mass of the optical system. Specifically, the present invention provides an optical amplifier that has a plurality of active and passive reflectors. The passive reflectors are oriented to fold the optical beam in a minimized volume and direct the optical beam repeatedly at the active reflectors to amplify the optical beam to a selected power level. The folding aspects of the optical reflectors may also decrease the operating temperature of the optical system.

Abstract: A phase conjugate laser mirror employing Brillouin-enhanced four wave mixing allows multiple independent laser apertures to be phase locked producing an array of diffraction-limited beams with no piston phase errors. The beam combiner has application in laser and optical systems requiring high average power, high pulse energy, and low beam divergence. A broad range of applications exist in laser systems for industrial processing, especially in the field of metal surface treatment and laser shot peening.

Abstract: An optical fiber amplifier has an amplification stage that uses an optical fiber pumped with pump energy of a first wavelength that oscillates through the gain medium. In one embodiment, the pumping is essentially a cavity resonator that is coupled to either end of the optical fiber such that oscillating pump energy is directed into one end of the fiber and out the other, as it reflects back and forth between the ends of the cavity. Highly reflective gratings are used to maintain the oscillation of the pump energy, and a pump energy source, such as pumped doped optical fiber, is coupled to at least one of the gratings. In another embodiment, the pump source comprises multiple reflectors that are employed at each end of the fiber, and independent pump sources each having a slightly different wavelength within the absorption spectrum of the amplifier are coupled together, such that two pump wavelengths are simultaneously oscillated through the gain medium.

Abstract: A technique for polarization locking optical outputs of N optical amplifiers to a reference polarization output, N being an integer, includes providing N optical loops and a reference optical loop. Each of the N optical loops includes a polarization controller connected to an optical amplifier. The reference optical loop includes a reference polarization controller and a linear optical polarizer. An optical output from a laser source is fed to all of the polarization controllers. A portion of an optical output of the reference polarization controller is fed back to an input of the reference polarization controller via the linear polarizer. A portion of the optical output of the reference polarization controller is fed to an optical input of each of N beam splitters and an optical output of each amplifier of the N loops is fed to an optical input of a respective one of the N beam splitters. A substantial portion of the optical output of each amplifier is output by its respective beam splitter.

Abstract: An optical waveguide including a single-mode waveguide in which an induced radiation ray generated by exciting the ion propagates in a single-mode in both of a thickness direction and a width direction in the single-mode waveguide; and multi-mode waveguides disposed along both of side surfaces of the single-mode waveguide in which the ray propagates in a single-mode in a thickness direction of the multi-mode waveguide and propagates in a multi-mode in a width direction. In accordance with the present invention, the exciting ray is easily absorbed because the ray propagates to cross the single-mode waveguide without a skew-mode propagation, and the laser and the photo-amplifier which can obtain a higher output in the single-mode is provided.

Abstract: The invention relates to devices for the quantum-optical amplification of modulated light, in particular in optical free-space communications systems. In the process a light beam (4) is conducted through a plurality of adjoining crystals (66), (68), (70), which are delimited from each other by means of polarization-selectively reflecting layers (104), (106). The light beam (4) is repeatedly reflected at the edge areas of the crystals into quarter-wave plates (86), (88), (90), (92), (94), and in the process its polarization is respectively rotated by 90 degrees.

Abstract: A semiconductor optical amplifier includes an optical signal input and an active section surrounded by two mirrors. A current is applied to the second mirror, for example by a current generator. Thus, the central wavelength of the reflection range of the second mirror is modifiable, the loss of the semiconductor-optical amplifier is changeable and the gain of the amplifier is adjustable.

Abstract: A method for tuning a dielectric filter comprises determining filter characteristics of a filter including a cut-on wavelength and a cut-off wavelength taken at a selected gain level. The filter is rotatably attached to a collimator assembly and a light source having a wavelength approximately equal to the cut-on frequency is applied to the filter and rotated to adjust the filter to the cut-on wavelength, and the spectral performance is measured and compared with a cut-on rating value. The method further includes applying a light signal having a wavelength set to a cut-off wavelength, to the filter rotating the filter relative to the collimator assembly, measuring spectral performance, and comparing the measured spectral performance with a cut-off rating value.

Abstract: A low-loss comb-generating optical cavity including an optical amplifier and a microwave-driven electro-optic modulator crystal, produces a comb of optical frequency sidebands having spectral lines equally spaced around the frequency of an input laser beam incident on the comb-generating cavity. The comb-generating cavity includes an input mirror movable along the beam propagation direction, and a fixed position output mirror located at time synchronous distances of both the input laser wavelength and modulation wavelength. The comb-generating cavity and its microwave driven modulator are in resonance with the input laser beam, and provide iterative or recirculating beam action that transfers the input optical frequency of the laser, sideband by sideband, to remote and precisely known comb frequencies offset from, and centered on, the input laser frequency.

Abstract: Within a vacuum vessel 10, there are arranged an electron gun 2 emitting an electron beam and an amplification part 3 which amplifies incident light 7 by means of the energy of the electron beam. The amplification part 3 is formed by two wave-like mirrors 4 and 5 made of a metal such as Ag or a multi-layer structure of dielectric materials, said mirrors being separated from each other to constitute not only an electron beam travelling part, but also a light input part 4a, 5a, a light amplifying part 4b, 5b and a light output part 4c, 5c arranged in this order viewed in a travelling direction of the electron beam. The light is made incident upon the light input part at a given incident angle, and propagates along the wave-like or zigzag optical waveguide within the light amplifying part by repeating reflections. Therefore, the wavenumber of the light is increased, and the light is amplified in a unidirectional manner by the energy of the electron beam.

Abstract: An optical amplifier for use with a solid state laser which includes a pair of elongated slabs of a solid state lasing material, such as a rare earth doped yttrium-aluminum-garnet (YAG) crystal. Two embodiments of the invention are disclosed. In both embodiments of the invention, each of the elongated slabs is formed with a square or generally rectangular cross-section. The slabs are configured such that the longitudinal axes of the slabs are generally co-axial aligned and the slabs are orientated such that the major axis of the slabs are generally orthogonal. By configuring the two slabs to be orthogonal with respect to one another, the integrated thermal lens becomes azimuthally symmetric and can be compensated by a simple external lens. In addition, the negative lensing affect along the major axis of one slab is used to compensate for the positive lensing affect along the minor axis of the other slab and vice versa, thus minimizing the affects of the astigmatism.

Abstract: There is disclosed a technique regarding an optical amplifier in an optical communications system. In order to effectively suppress optical surges during amplification of signal light, through a simple structure, there is provided an amplifying medium which amplifies input light and outputs the amplified light, and reflecting members are connected to the input and output sides of the amplifying medium. The reflecting members can reflect light with a predetermined optical wavelength different from a signal light wavelength contained in the input light.

Abstract: An Erbium doped fiber amplifier (EDFA) is placed in a laser cavity to clamp the gain of the amplifier. The laser cavity is preferably formed to minimize the effects of relaxation oscillations and of spectral hole burning. In a preferred embodiment, the laser cavity supports a lasing wavelength which makes the saturation energy at the laser wavelength less than that at the signal wavelengths. In an erbium doped fiber implementation, the laser wavelength is shorter than that of the signal wavelengths and is separated from them by no more than approximately 75% of the width of the spectral hole. The compounding of relaxation oscillations may be substantially eliminated by varying the length of the fiber within each laser cavity within a system to change the photon round-trip time within each cavity.

Abstract: This invention describes new developments in Sagnac Raman amplifiers and cascade lasers to improve their performance. The Raman amplifier bandwidth is broadened by using a broadband pump or by combining a cladding-pumped fiber laser with the Sagnac Raman cavity. The broader bandwidth is also obtained by eliminating the need for polarization controllers in the Sagnac cavity by using an all polarization maintaining configuration, or at least using loop mirrors that maintain polarization. The polarization maintaining cavities have the added benefit of being environmentally stable and appropriate for turn-key operation. The noise arising from sources such as double Rayleigh scattering is reduced by using the Sagnac cavity in combination with a polarization diversity pumping scheme, where the pump is split along two axes of the fiber. This also leads to gain for the signal that is independent of the signal polarization.

Abstract: A 1.3 .mu.m-band optical amplifier includes an optical amplifying fiber doped with Yb ion for emitting light in 1.02 .mu.m band by pumping of the 0.98 .mu.m band light and Pr ion for amplifying signal light by pumping of the 1.02 .mu.m band light. Both ends of the optical amplifying fiber are connected to optical fiber gratings for selectively reflecting 1.02 .mu.m band light via matching connecting members and tapered core optical fibers. The optical fiber gratings form a 1.02 .mu.m-band resonator. A Wavelength Division Multiplexing (WDM) optical coupler multiplexes the signal light and pumping light from an pumping laser and supplies the thus-multiplexed light to the optical fiber grating. The pumping laser comprises a laser device which causes laser oscillation at 0.98 .mu.m. A 1.5 .mu.m-band optical amplifier having a similar configuration is also disclosed.

Abstract: An Erbium doped fiber amplifier (EDFA) is placed in a laser cavity to clamp the gain of the amplifier. The laser cavity is preferably formed to minimize the effects of relaxation oscillations and of spectral hole burning. In a preferred embodiment, the laser cavity supports a lasing wavelength which makes the saturation energy at the laser wavelength less than that at the signal wavelengths. In an erbium doped fiber implementation, the laser wavelength is shorter than that of the signal wavelengths and is separated from them by no more than approximately 75% of the width of the spectral hole. The compounding of relaxation oscillations may be substantially eliminated by varying the length of the fiber within each laser cavity within a system to change the photon round-trip time within each cavity.

Abstract: In a gain-controlled erbium-doped optical amplifier, gain control is achieved by clamping the gain of a laser cavity to be equal to the overall cavity loss and by fixing the resonant wavelength of the amplifier to be at a first wavelength. When an optical signal to be amplified having a second wavelength different from the first wavelength passes through the amplifier the gain experienced by the signal depends entirely on the gain of the cavity, and not on the intensity of the signal. If the first wavelength is arranged to be at the peak of the sum of the absorption and emission cross sections of erbium, the amplifier exhibits minimum sensitivity to ambient changes in temperature.

Abstract: An optical fiber amplifier which receives a primary laser beam and generates a coherent amplified laser beam, includes an optical isolator which transmits the primary laser, a 3-dB coupler which receives the primary laser beam, which generates first and second laser beams, which receives first and second amplified laser beams, and which combines the amplified laser beams to thereby produce the coherent amplified laser beam, a phase controller operatively connected in parallel with the 3-dB coupler which controls the phase of each of the amplified laser beams, and first and second fiber amplifiers operatively connected to the 3-dB coupler, the fiber amplifiers receiving first and second laser beams and generating the amplified laser beams, respectively. A high power coherent laser amplifier utilizing several optical fiber amplifier networks connected to one another in parallel is also described.

Abstract: The gain provided by an erbium amplifier is stabilised by spectrally selective optical feedback to make the amplifier lase. The resulting laser emission is extracted from the amplifier output using a Mach Zehnder with matched Bragg reflectors in its two interference arms. The extracted light may be used for supervisory purposes. Part of the laser cavity defining feedback may be provided by the Mach Zehnder by arranging one of its Bragg reflectors to be displaced with respect to the other.

Abstract: The conversion efficiency of a cascaded Raman laser (CRL) can be significantly improved if it comprises one or more of the below recited design features. The CRL comprises an intracavity section between an input section and an output section. The CRL is adapted for receiving pump radiation of wavelength .lambda..sub.p, and for emitting output radiation of wavelength .lambda..sub.n >.lambda..sub.p, and each of the input section and output section comprises fiber Bragg gratings of center wavelengths .lambda..sub.1, .lambda..sub.2 . . . .lambda..sub.n, where n.gtoreq.2 and .lambda..sub.1 <.lambda..sub.2 < . . . .lambda..sub.n-1. Among the efficiency-increasing features is ordering of the fiber Bragg gratings such that in the input section and the output section the gratings of center wavelengths .lambda..sub.1 . . . .lambda..sub.n and .lambda..sub.1 . . . .lambda..sub.

Abstract: A laser system has a high reflector and an output coupler defining a laser cavity with an optical axis. Included is a pump source, a mode-locking apparatus and at least one fold mirror positioned in the laser cavity along the optical axis. A gain media is positioned adjacent to the fold mirror. The gain media has an overlap region where an intracavity beam entering the gain media substantially overlaps the intracavity beam exiting the gain media.

Abstract: A semiconductor diode laser amplifier (100) includes an active layer (4) which is situated between two cladding layers (1A, (3,6)) and in which a strip-shaped active region is present which is bounded in longitudinal direction by two end faces (7,8) which are practically perpendicular to the active region and are provided each with an antireflection layer (71,81).The amplification ripple of such a laser amplifier (100) is comparatively high, in particular when radiation of different wavelengths is present in the laser (100), such as the TE and TM portions of the radiation to be amplified.

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