Abstract: An exemplary backlight module (40) includes a number of point light sources (43) and a light-mixing member (47). The number of point light sources emit light beams of different colors. The light-mixing member mixes the light beams of different colors into white light beams. The light-mixing member includes a light entrance surface (470) opposite to the light sources. The light entrance surface includes a number of recesses (471). The recesses correspond to the number of point light sources. The backlight module has high efficiency of light mixing.

Abstract: A guiding nonlinearity cell. The novel nonlinearity cell includes a nonlinear medium and a waveguide adapted to guide input electromagnetic energy through the nonlinear medium. In an illustrative embodiment, the cell includes a thin layer of a liquid or solid nonlinear medium disposed between two parallel plates adapted to guide energy through the length of the medium by total internal reflection. The plates can be made from a material having a refractive index less than a refractive index of the medium to provide total internal reflection within the liquid, or they can be made from a material matching the refractive index of the medium such that outer walls of the plates provide total internal reflection, allowing energy to leak into the plates.

Abstract: A system for optical communication including an optical amplifier card configured to receive a plurality of pump laser modules. The optical amplifier card includes a receptacle configured to receive the pump laser module, a connector configured to couple the pump laser module to the optical amplifier card, a monitor configured to measure at least the optical output power of the pump laser module, and a pump combiner communicatively coupled to the monitor. The pump combiner is configured to receive a signal from the monitor indicating a drop in the output power of a first pump laser module below a threshold level, and, in response to the signal, switch the optical amplifier card from using the optical power of the first pump laser module to using the optical power of a second pump laser module without substantially affecting normal operation of the optical amplifier card.

Abstract: Laser light emission across a wide bandwidth emission spectrum is enabled in a laser device equipped with solid gain media. The laser device is equipped with: a resonator; a plurality of solid gain media, having fluorescent spectra that at least partially overlap with each other, provided within the resonator; and pumping means, for pumping the plurality of solid gain media. The entire fluorescent spectrum width of the plurality of solid gain media is greater than the fluorescent spectrum width of each solid gain medium.

Abstract: Laser light emission across a wide bandwidth emission spectrum is enabled in a laser amplifier equipped with solid gain media. The laser amplifier is equipped with: a resonator; a plurality of solid gain media, having fluorescent spectra that a least partially overlap with each other, provided within the resonator; and pumping means, for pumping the plurality of solid gain media. The entire fluorescent spectrum width of the plurality of solid gain media is greater than the fluorescent spectrum width of each solid gain medium.

Abstract: A laser and amplifier combination delivers a sequence of optical pulses. Pulses from the laser are temporally stretched by a pulse stretcher before amplification and temporally compressed by a pulse compressed after amplification. The pulse stretcher includes a diffraction grating on which pulses being compressed are incident. An arrangement is provided for measuring the carrier-envelope phase of the pulses and adjusting the incidence angle of pulses on the grating cooperative with the measurement such that the carrier envelope phase of the pulses in the sequence is about constant.

Abstract: An integrated optical-amplification module includes a housing member, a first input optical terminal configured to receive an optical signal, a second input, optical terminal that can receive a pump light, and an output optical terminal that can output a combined optical signal comprising at least a portion of the optical signal and a portion of the pump light. The integrated optical-amplification module also includes an optical combiner fixedly installed relative to the housing member. The optical combiner can receive the pump light and the optical signal and an optical prism fixedly installed relative to the housing member. The optical combiner can merge the pump light and the optical signal to form the combined optical signal. The optical prism can direct at least a portion of the optical signal through free space to the optical combiner.

Abstract: There is provided a long-band rare-earth-doped optical amplifier and method for amplifying an optical signal. The optical amplifier has a pre-, a mid- and a post-amplification stage. Only the mid-amplification stage is pumped with a pump light source. The other two are pumped using Amplified Spontaneous Emission (ASE) generated in the mid-amplification stage. An optical coupling device is used to couple the three amplification stages together and to split the ASE generated in the mid-amplification stage and available at one end of the mid-amplification stage. One part of the split ASE is used to pump the pre-amplification stage while the other part is used to pump the post-amplification stage.

Abstract: Devices are disclosed herein which may comprise an EUV reflective optic having a surface of revolution that defines a rotation axis and a circular periphery. The optic may be positioned to incline the axis at a nonzero angle relative to a horizontal plane, and to establish a vertical projection of the periphery in the horizontal plane with the periphery projection bounding a region in the horizontal plane. The device may further comprise a system delivering target material, the system having a target material release point that is located in the horizontal plane and outside the region, bounded by the periphery projection and a system generating a laser beam for irradiating the target material to generate an EUV emission.

Abstract: A high extraction efficiency laser system. The novel laser system includes a laser amplifier and a laser source adapted to provide a laser beam to the amplifier such that polarization states for incident and reflected light within the amplifier are perpendicular one to another. In an illustrative embodiment, the laser beam is input to the amplifier such that the beam reflects back and forth between the side walls of the amplifier with an angle of incidence of about 45 degrees, and the laser beam is linearly polarized in the plane of incidence. This arrangement reduces interference fringes in the amplifier. In an alternative embodiment, the system includes an aberrator adapted to add time-varying aberrations in the laser beam at a rate exceeding an inversed lifetime of an inverted population in the amplifier to increase spatial homogenization of saturation and extraction patterns in the amplifier.

Abstract: The specification describes optical devices and related methods wherein an input mode is converted by multiple LPG mode transformers to produce an output with multiple predetermined modes.

Abstract: An integrated semiconductor optical device and an optical module capable of the high-speed and large-capacity optical transmission are provided. In an integrated semiconductor optical device in which a plurality of optical devices buried with semi-insulating semiconductor materials are integrated on the same semiconductor substrate and an optical module using the integrated semiconductor optical device, configurations (material and electrical characteristics) of the buried layers are made different for each of the optical devices.

Abstract: An apparatus includes a first optical amplifier that uses a rare-earth-doped optical medium, an isolator that inputs amplified light amplified by the first optical amplifier, a second optical amplifier that uses a rare-earth-doped optical medium to amplify a light output from the isolator, and a first light router that routes amplified spontaneous emission light generated by the first optical amplifier or the second optical amplifier to input, by a second light router, the routed amplified spontaneous emission light to the optical rare-earth-doped medium other than the optical rare-earth-doped medium where the routed amplified spontaneous emission light is generated.

Abstract: The polarization direction of an optical signal is changed by a polarization controller so as to be orthogonal to a main axis of a polarizer. A control pulse generator generates control pulses from control beam with a wavelength which is different from the wavelength of the optical signal. The optical signal and the control pulse are input to a nonlinear optical fiber. In the nonlinear optical fiber, the optical signal, during a time period in which the optical signal and the control pulse coincide, is amplified with optical parametric amplification around a polarization direction of the control pulse. The optical signal, during the time period in which the optical signal and the control pulse coincide, passes through the polarizer.

Abstract: Methods and systems are provided for generation and detection of rogue waves, including hydrodynamic rogue waves and optical rogue waves. A method for generating an optical rogue wave comprises the steps of generating an input pulse into a nonlinear optical medium, and perturbing the input pulse by directing a narrow-band seed radiation into the input pulse. The seed radiation has a frequency and timing to generate broadband radiation within the nonlinear optical medium.

Abstract: An integrated photonics module includes at least one light source and a MEMS scanner coupled to and held in alignment by an optical frame configured for mounting to a host system. According to some embodiments, the integrated photonics module may include a plurality of light sources and a beam combiner coupled to the optical frame. According to some embodiments, the integrated photonics module includes a selective fold mirror configured to direct at least a portion of emitted light toward the MEMS scanner in a normal direction and pass scanned light through to a field of view. The selective fold mirror may use beam polarization to select beam passing and reflection. The integrated photonics module may include a beam rotator such as a quarter-wave plate to convert the polarization of the emitted light to a different polarization adapted for passage through the fold mirror. The integrated photonics module may include one or more light detectors.

Abstract: A polymer-based optical waveguide amplifier comprises a polymer host material doped with rare earth ions wherein the polymer host material is a material that functions as a resist in a direct patterning technique. The polymer host material can be epoxy novalac resin doped with Er3+ ions and Yb3+ ions, and the direct patterning comprises electron beam direct writing or UV printing.

Abstract: A pulse stretcher includes a plurality of substantially parallel slab-like optical paths of different optical path lengths and a plurality of reflecting surfaces, which are totally internally reflecting surface formed, located at an end of the corresponding optical path. Due to the different path lengths, the pulse stretcher can spread out an input pulse into a stretched pulse having a longer pulse duration and proportionally lower intensity than the initial pulse.

Abstract: The invention concerns a laser system with a frequency comb generator for generating a comb of optical frequencies having an offset frequency and a plurality of equidistant modes. The laser system further preferably includes at least one stabilizer for stabilizing the frequency comb onto a certain offset frequency and/or onto a certain mode spacing. The laser system further includes an optical amplifier for amplifying the frequency comb coupled out of the frequency comb generator, the amplification factor of this amplifier being variable; and the amplifier is followed by a Raman medium for generating a Raman shift of the frequency comb.

Abstract: A high extraction efficiency laser system. The novel laser system includes a laser amplifier and a laser source adapted to provide a laser beam to the amplifier such that polarization states for incident and reflected light within the amplifier are perpendicular one to another. In an illustrative embodiment, the laser beam is input to the amplifier such that the beam reflects back and forth between the side walls of the amplifier with an angle of incidence of about 45 degrees, and the laser beam is linearly polarized in the plane of incidence. This arrangement reduces interference fringes in the amplifier. In an alternative embodiment, the system includes an aberrator adapted to add time-varying aberrations in the laser beam at a rate exceeding an inversed lifetime of an inverted population in the amplifier to increase spatial homogenization of saturation and extraction patterns in the amplifier.

Abstract: The present invention provides a rare-earth ions doped, especially erbium and ytterbium doped transparent electro-optic gain ceramic material consisting lead, zirconium, titanium and lanthanum. The electro-optic gain ceramic material either has a linear electro-optic coefficient or a quadratic electro-optic coefficient, which is greater than about 0.3×10?16 m2/V2 for the latter, a propagation loss of less than about 0.3 dB/mm, and an optical gain of great than 1.5 dB/mm at a wavelength of about 1550 nm while optically pumped by a 1.4 watts diode laser at a wavelength of 970 nm at 20° C. The present invention also provides electro-optic devices including a rare-earth ions doped, especially erbium and ytterbium doped, transparent electro-optic gain ceramic material consisting lead, zirconium, titanium and lanthanum.

Abstract: An on-chip amplifier includes first element that curtails the velocity of an incoming light to the amplifier. A second element is doped so as to make the frequency of the incoming light equal to the electron frequency in order to allow for electron-photon wave interaction, so that when current flows through the amplifier, electron power is transferred to the incoming light, resulting in amplification of the incoming light.

Abstract: A chirped pulse amplification (CPA) system and method is described wherein a pulse selector is added after a final amplifier in the system. The pulse selector is configured to select amplified pulses such that the system output repetition rate of the CPA system is below an ASE-limiting repetition rate of the amplifiers. The system may also comprise pulse pickers placed before the final amplifier to control pulse energy of the amplified pulses.

Abstract: Methods and systems for optical chirped pulse amplification and phase dispersion, the system including an active dispersion controller for receiving an input optical pulse from a modelocked laser and controlling a third and fourth order dispersion property of the input optical pulse to produce an optical output pulses, a stretching re-circulating loop for stretching the optical output pulses in time, an optical amplifier for amplifying the stretched optical output pulses, a compressing re-circulating loop for compressing the amplified stretched optical output pulse to produce a compressed optical output pulse, and a feedback loop for feeding a feedback optical signal to the active dispersion controller.

Abstract: A method and apparatus for monitoring spectral tilt uses an arrayed waveguide grating (AWG) to separate a multiplexed optical signal having a plurality of wavelength channels into a plurality of sub-bands, where each sub-band spans a different wavelength range and includes more than one wavelength channel. A photodetector array is provided to measure the optical power in each of the sub-bands, while control electronics calculate spectral tilt of the multiplexed optical signal using the measured optical power in each of the sub-bands. The spectral tilt monitor in accordance with the instant invention provides spectral resolution, increased monitoring speeds, and decreased manufacturing costs.

Abstract: Provided is an ultra-short pulse light source having an optical pulse generator 111 for emitting short pulse light, an optical amplifier 112 for amplifying the short pulse light output from the optical pulse generator 111 and an optical compressor 120 for compressing the short pulse light. The optical compressor 120 has multi-step configuration of steps polarization beam splitters 1211,2, optical fibers 1221,2,1231,2 for compressing the incident pulse light, polarization rotating element 1241,2, for rotating the polarization direction of the incident light by 90 degrees to return the light to the optical fibers 1231,2, polarization maintaining optical fibers 1251,2 provided to the output side of the polarization beam splitters 1211,2, and a polarization maintaining optical fiber 1251 at the front step is connected to a polarization maintaining optical fiber 1252 at the rear step.

Abstract: The present invention purposes to provide a THz-wave generator capable of generating a THz-wave stably and efficiently, and particularly, to provide the THz-wave generator which is stable against a frequency shift of a laser source and which can easily vary the frequency of the THz-wave. A THz-wave generator, for inputting a laser beam from a light source unit A including a laser source to a THz-wave generating element D, and generating a THz-wave (fT) from the THz-wave generating element, wherein a light circulating unit including an SSB optical modulator, and wavelength selecting means C are disposed between the laser source A and the THz-wave generating element D, the laser beam is guided into the light circulating unit, a specific wavelength lightwave is selected out of lightwaves having a plurality of wavelengths generated in the light circulating unit by the wavelength selecting means, and the specific wavelength (f0, fn) lightwave is input to the THz-wave generating element.

Abstract: A metallic nano-particle surrounded by an amplifying medium results in a boundary condition that creates a singularity in the particle's dynamic polarizability at the localized surface plasmon resonance and at a critical value of the gain is disclosed. The boundary condition may be time dependent due to excitation by a sub-picosecond laser pulse and couples to the electromagnetic vacuum resulting in photon emission in an analogue of the Unruh Effect. The vacuum emission from 2-D nanostructures embedded in high gain laser dyes predicts energies nearly two orders of magnitude larger than the spontaneous emission background. The vacuum radiation is may have a unique dependence on the excitation.

Abstract: A method and apparatus use a photonic-crystal fiber having a very large core while maintaining a single transverse mode. In some fiber lasers and amplifiers having large cores problems exist related to energy being generated at multiple-modes (i.e., polygamy), and of mode hopping (i.e., promiscuity) due to limited control of energy levels and fluctuations. The problems of multiple-modes and mode hopping result from the use of large-diameter waveguides, and are addressed by the invention. This is especially true in lasers using large amounts of energy (i.e., lasers in the one-megawatt or more range). By using multiple small waveguides in parallel, large amounts of energy can be passed through a laser, but with better control such that the aforementioned problems can be reduced. An additional advantage is that the polarization of the light can be maintained better than by using a single fiber core.

Abstract: An amplifying optical electromagnetic wave concentrator includes an amplification focusing device and a receiver. The amplification focusing device focuses an incident optical electromagnetic wave on the receiver. The amplification focusing device is doped with active components and is subjected to an excitation wave that causes the active components to pass to an energy level such that interaction between the incident electromagnetic wave and the active components causes the active components to pass to a lower energy level and causes emission, towards the receiver, of at least one photon having the same wavelength as the incident electromagnetic wave. The focused photon or photons form an amplified wave of the incident electromagnetic wave.

Abstract: The invention relates to a regulatable optical amplifier which has at least two series-connected amplifier groups, each amplifier group having a regulating device. Connected upstream of the optical amplifier is a power monitor device for detecting changes in the input power, whose electrical output is connected both to the first regulating device and to the second regulating device. In line with the invention, the first and second regulating devices have a control line inserted between them which comprises a series circuit containing a high-pass filter, a delay and signal-shaping unit and a feed-forward control unit for generating a correction signal for the second regulating device. In this arrangement, the high-pass filter has a cut-off frequency which corresponds approximately to the cut-off frequency of the first amplifier group.

Abstract: An optical filter and methods of filtering are provided. The optical filter includes a hollow-core fiber including a first portion and a second portion. The first portion includes a hollow core having a first diameter and a cladding having a second diameter. The second portion includes a hollow core having a third diameter smaller than the first diameter and a cladding having a fourth diameter smaller than the second diameter.

Abstract: A high-speed optical amplifier is considered to be an important optical device because of an increasing demand of routing, which is accompanied by an increase in complexity of networks. It is difficult to satisfy a response performance by related-art techniques, and there has been a problem in achieving a high-speed response performance of 10 microseconds or less. An optical amplifier according to the present invention includes: an input monitor means 500; an optical amplification means 310 including an optical amplification medium 300, and a control means 400 for performing feed-forward control. When the optical amplification means is controlled by the feed-forward control in response to a signal of the input monitor means 500, an overshoot signal is applied as a control signal so that a slow response performance specific to the optical amplification medium has been improved, and thereby high-speed response performance has been achieved.

Abstract: The present invention relates to an amplifier chain for generating ultrashort light pulses of different pulse durations and applies in particular to amplifier chains suitable for amplifying picosecond and femtosecond pulses. The amplifier chain comprising a stretcher with at least one entry dispersive element of the grating type and intended to temporally stretch an incident pulse, an amplifying medium designed to amplify said stretched pulse, a compressor with at least one entry dispersive element substantially identical to that of the stretcher, designed to temporally compress said amplified pulse. According to the invention, the stretcher and the compressor include means for moving the dispersive elements between first and second positions, in such a way that the angle of incidence in a first position is equal to the angle of diffraction in the second position, and vice versa, allowing two degrees of stretch of the chain to be defined, each adapted to the amplification of pulses of different durations.

Abstract: Phase-sensitive amplification (PSA), which is produced by degenerate four-wave mixing (FWM) in a randomly-birefringent fiber, has the potential to improve the performance of optical communication systems. Scalar FWM, which is driven by parallel pumps, is impaired by the generation of pump-pump and pump-signal harmonics, which limit the level, and modify the phase sensitivity, of the signal gain. In contrast, vector FWM, which is driven by perpendicular pumps, is not impaired by the generation of harmonics. Vector FWM produces PSA with the classical properties of a one-mode squeezing transformation.

Abstract: A spatially-fed high-power amplifier comprises one or more shaped reflectors to reflect an initial wavefront, and an active array amplifier to amplify the reflected wavefront to generate a high-power planar wavefront. The shaped reflectors provide the reflected wavefront with substantially uniform amplitude when incident on the active array amplifier. The initial wavefront may be a substantially spherical wavefront, and the shaped reflectors may compensate for any amplitude taper of the initial wavefront to provide the reflected wavefront with substantially uniform amplitude components for incident on the active array amplifier. In some embodiments, the shaped reflectors may also contour the illumination to fit the shape of the active array amplifier to help minimize spillover.

Abstract: The present invention relates to an assembly of multiple waveguides which includes a substrate and a plurality of waveguides positioned on said substrate at locations effective to suppress cross-talk between different waveguides. The plurality of waveguides each comprise an elongate array of quantum dots extending between sets of first and second locations on the substrate. The waveguides are positioned to receive: (1) pumped light uniformly applied to the array to produce electron-hole pairs and to enable optical gain and (2) signal light at the first location to trigger an emission from the quantum dot at the first location and transmission of photons along the array to the second location. A light transmission system which includes this assembly as well as methods of making and using the assembly are also disclosed.

Abstract: The present invention provides an organic/inorganic composite containing a rare earth metal or/and Period IV transition metal in which the aforementioned rare earth metal or/and Period IV transition metal is doped at a high concentration, and control of quenching and optical transparency are assured thereby; and an optical amplifier, a light control optical element, and luminescent device utilizing the same. The organic/inorganic composite containing a rare earth metal or/and Period IV transition metal is one in which at least one species of rare earth metal or/and Period IV transition metal is dispersed in an organic polymer, with the aforementioned composite containing an optically transparent organic polymer and an inorganic dispersion phase comprising: (1) a rare earth metal and (2) another element coordinated thereto via an oxygen atom(s).

Abstract: A system, method, and computer readable medium for converting paper documents (134) to electronic documents (138) and sending the electronic documents (138) to at least one destination (144).

Abstract: An EUV light source device properly compensates the wave front of laser beam which is changed by heat. A wave front compensator and a sensor are provided in an amplification system which amplifies laser beam. The sensor detects and outputs changes in the angle (direction) of laser beam and the curvature of the wave front thereof. A wave front compensation controller outputs a signal to the wave front compensator based on the measurement results from the sensor. The wave front compensator corrects the wave front of the laser beam to a predetermined wave front according to an instruction from the wave front compensation controller.

Abstract: A WDM system includes a plurality of P to P WDM systems connected for wavelength-multiplexing optical signals of a plurality of wavelengths, transmitting them to a transmission path, transmitting wavelength-division multiplexed light while performing amplification by using optical AMP in the transmission path, and subjecting the wavelength-division multiplexed light to wavelength isolation at the reception side. An OSC which is a monitoring control signal such as a normal optical signal is used closely within one P to P WDM system. However, by transmitting and receiving the OSC between a plurality of P to P WDM systems, it is possible to solve a problem at the system rise. Moreover, since accumulative OSNR data is transmitted up to the P to P WDM system of the final stage, it is possible to detect an accurate OSNR value and a leak ASE light quantity at the end side.

Abstract: In the three-terminal optical signal amplifying device 10, a portion of the neighboring light LS at other wavelength than that of the first wavelength ?1 that is selected from the output light from the element 14 by the optical add drop filter 16, and the control light Lc at the second wavelength ?2 input from the external are together input to the second semiconductor optical amplifying element 18. The output light including the output signal light LOUT at the second wavelength ?2 and the neighboring light at the neighboring wavelength to the second wavelength ?2 that is modulated and controlled by the control light LC in the cross gain modulation is output from the second semiconductor optical amplifying element 18. And the output signal light LOUT at the second wavelength ?2 passes through the wavelength selecting filter 20.

Abstract: The present invention relates to an adjustable optical signal delay module, particularly to a module, which adjusts power of an amplified spontaneous emission generated by a semiconductor optical amplifier and reversely feeds the adjusted amplified spontaneous emission back to the semiconductor optical amplifier to vary a group refractive index of the semiconductor optical amplifier and delay the timing of an optical signal, whereby the present invention can replace the pump laser conventionally required by a CPO mechanism. In the present invention, the feedback optical loop comprises a variable optical attenuator, an optical filter, and optical circulators. An user can control the delay timing of optical signals via adjusting optical power in the feedback optical loop. The present invention can decrease the fabrication cost of an optical signal delay module and reduce the volume thereof.

Abstract: The present invention provides an optical switch including a loss element having a signal loss, and a rare earth doped gain element optically connected in series with the loss element. The rare earth doped gain element is operable to produce a signal gain. The signal gain and the signal loss are about equal. The present invention also provides a method of optical switching including optically connecting a loss element in series with a rare earth doped gain element and passing an optical signal through the loss element and the gain element. The loss element attenuates the optical signal by a first amount. The method further includes selectively applying an optical pump to the gain element to perform the switching, the gain element amplifying the optical signal by the first amount in response to the optical pump.

Abstract: The high-power-optical-amplifier of the present invention uses a number of spaced, thin slabs (e.g., disc-shaped doped-slabs that are stacked, with a space between discs), aligned to give an amplifier both with a high active cross-section and a very high surface area to volume ratio. More specifically, the present invention provides several methods that include the steps of aligning at least two or four slabs having a thickness dimension of less than one centimeter, substantially parallel to, and spaced from adjacent slabs, wherein the slab surfaces are rendered essentially non-reflective, optically pumping the slabs and passing an input beam through the surfaces wherein the beam is optically amplified in the slabs, and wherein the input beam is of an eye-safe wavelength.

Abstract: An optical coupling device for coupling light with an optical waveguide comprises a mirror formed within an optical waveguide. The mirror comprises a first material, a first reflective end, and a second reflective end. The first material is light conducting and has a first refractive index. The first and second reflective ends reflect and transmit light. The mirror has an axis line. The optical coupling device is useful for extracting light from a waveguide and providing a backlight for a liquid crystal display.

Abstract: An optical switch assembly comprising at least two optical amplifiers (10, 20), means for applying a first input signal to one end of both amplifiers (10, 20) and a second input signal to another end, and means for simultaneously driving one or other of the amplifiers into a saturated state whilst the other is unsaturated such that only the amplifier that is unsaturated provides any significant amplification to the input signals at each end, and means for feeding the amplified output signals from the amplifiers to at least two output nodes such that the two amplifiers (10, 20) are connected to the two output nodes in opposite connections.

Abstract: Artificial materials, such as metamaterials, include adjustable properties. In some approaches the properties are adjustable according to active feedback of interaction with electromagnetic waves.

Abstract: The invention describes techniques for the control of the spatial as well as spectral beam quality of multi-mode fiber amplification of high peak power pulses as well as using such a configuration to replace the present diode-pumped, Neodynium based sources. Perfect spatial beam-quality can be ensured by exciting the fundamental mode in the multi-mode fibers with appropriate mode-matching optics and techniques. The loss of spatial beam-quality in the multi-mode fibers along the fiber length can be minimized by using multi-mode fibers with large cladding diameters. Near diffraction-limited coherent multi-mode amplifiers can be conveniently cladding pumped, allowing for the generation of high average power. Moreover, the polarization state in the multi-mode fiber amplifiers can be preserved by implementing multi-mode fibers with stress producing regions or elliptical fiber cores These lasers find application as a general replacement of Nd: based lasers, especially Nd:YAG lasers.

Abstract: Provided is a fiber ring laser capable of obtaining a back-up laser light and standard light having a wavelength continuously tuned in a single mode with equal spacing of 12.5 GHz, 25 GHz, 50 GHz or 100 GHz recommended by ITU-T Recommendation G. 692 & G. 694.1 in a C-band and an L-band using a fiber tunable etalon filter, an air gap etalon filter and a saturable absorber in an optical fiber laser resonator having a serial ring shape using a C-band optical amplifier and an L-band optical amplifier. The fiber ring laser can generate laser light having a wavelength tuned by more than 70 nm, excellent output power flatness and a source spontaneous emission ratio of more than 70 dB in 361 channels with equal spacing of 25 GHz by applying a bias voltage to a voltage-operated piezoelectric element of a tunable etalon filter. A single longitudinal mode operation of the fiber ring laser can be obtained by using a saturable absorber serving as a narrow-bandwidth filter.