Abstract: Liquid crystal waveguides for dynamically controlling the refraction of light. Generally, liquid crystal materials may be disposed within a waveguide in a cladding proximate or adjacent to a core layer of the waveguide. In one example, portions of the liquid crystal material can be induced to form refractive or lens shapes in the cladding that interact with a portion (e.g. evanescent) of light in the waveguide so as to permit electronic control of the refraction/bending, focusing, or defocusing of light as it travels through the waveguide. In one example, a waveguide may be formed using one or more patterned or shaped electrodes that induce formation of such refractive or lens shapes of liquid crystal material, or alternatively, an alignment layer may have one or more regions that define such refractive or lens shapes to induce formation of refractive or lens shapes of the liquid crystal material.

Abstract: A device, a method of fabricating the device and a sample analysis system that includes the device are provided. The device includes an optical waveguide having a plurality of nanofeatures integrated thereon to influence at least one of evanescence and coupling of an optical field of the optical waveguide. The sample analysis system includes a fluidic actuation system for introducing sample specimen fluid into a microfluidic channel of the device for evanescence based detection.

Abstract: An optical system is disclosed. The optical system includes first and second waveguides, a first dispersive element, and a coupler. The first waveguide is configured to support a first mode and a second mode of an optical input signal. The second mode being of a higher order than the first mode. The second waveguide has an input and an output and is configured to receive a portion of the optical input signal. The first dispersive element is disposed along a length of one of the first or second waveguides. The first dispersive element including a waveguide segment configured to induce a frequency-dependent phase shift in one of the portions of the optical input signal. The coupler is configured to couple the portion of the optical input signal in the second waveguide and the portion optical input signal in the first waveguide into the first waveguide. The coupling excites the second mode of the first waveguide to create a multimode optical signal.

Abstract: A system and method directed to an integrated fiber optic splitter assembly having at least two fused splitters disposed in a common substrate. An integrated optical splitter assembly includes a plurality of input fibers, a plurality of output fibers, and a plurality of splitters disposed on a single substrate to either split or couple optical signals between the input and output optical fibers.

Abstract: An optical fiber arrangement has at least two optical fiber sections, each optical fiber section defining an outside longitudinally extending surface. The outside longitudinally extending surfaces are in optical contact with each other. The invention further provides for an amplifying optical device have an optical fiber arrangement as just described, and a pump source. The amplifying optical device is configured such that the pump source illuminates the amplifying optical fiber. A amplifying arrangement is also disclosed. The amplifying arrangement includes a plurality of amplifying optical devices as just described, and each amplifier also has at least one input fiber and a first multiplexer connected to the input fiber. Each amplifier is configured such that at least one of the amplifying optical fibers is connected to the first multiplexer. The amplifying arrangement also has a second multiplexer connected to each of the first multiplexers.

Abstract: Complex, coupled photonic microdevices are formed to include sub-wavelength-sized radial perturbations sufficient to create resonant cavities, where these devices may be formed along the length of a single optical fiber and coupled together to form relatively complex photonic devices. By carefully selecting the placement and separation of these local radius variations, and using microfibers (or other suitable arrangements) to couple optical signals into and out of the device fiber, resonances in the form of whispering gallery modes (WGMs) are created in the device fiber such that a number of coupled microstructures (such as ring resonators) may be formed.

Abstract: A whispering gallery mode resonator based optical sensor assembly comprises a flow channel permeable to optical energy and first and second optical waveguides adjacent to a section of the flow channel and adapted to be in first and second evanescent field couplings respectively with the section such that the section forms a whispering gallery mode resonator. The resonator is responsive to an optical signal conveyed in the first optical waveguide and communicates a second optical signal to the second optical waveguide indicative of a resonance wavelength of the whispering gallery mode resonator. A detector optically coupled to the second optical waveguide detects the output signal. A signal processor detects a shift in the output signal responsive to an analyte fluid flowing through the flow channel. The shift is indicative of the identity of at least one constituent of the analyte fluid.

Abstract: An optical coupler includes a first waveguide configured to supply a first optical signal having a wavelength and a second waveguide. The first optical signal having a first mode. The first waveguide has a tapered portion being spaced from the second waveguide by a distance sufficient to facilitate evanescent coupling of the first optical signal from the first waveguide to the second waveguide. A first effective refractive index of the first waveguide at a location in the tapered portion being equal to a second effective refractive index at a location in the second waveguide. The first effective refractive index being associated with the first mode and the second effective refractive index being associated with a second mode of a second optical signal having the wavelength. The second mode having a different order than the first mode, and the second waveguide being configured to supply the second optical signal.

Abstract: A method fabricates an optical switch comprising a microsphere coated with silicon nanocrystals. The method includes providing a silica optical fiber. The method further includes melting at least a portion of the fiber to form at least one silica microsphere. The method further includes coating the microsphere with a silica layer. The method further includes precipitating silicon nanocrystals within the silica layer by annealing the microsphere. The method further includes passivating the nanocrystals by annealing the microsphere in a hydrogen-containing atmosphere.

Abstract: Various embodiments of the present invention are related to microresonator systems that can be used as a laser, a modulator, and a photodetector and to methods for fabricating the microresonator systems. In one embodiment, a microdisk comprises: a top layer; a bottom layer; an intermediate layer having at least one quantum well, the intermediate layer sandwiched between the top layer and the bottom layer; a peripheral annular region including at least a portion of the top, intermediate, and bottom layers; and a current isolation region configured to occupy at least a portion of a central region of the microdisk including at least a portion of the top, intermediate, and bottom layers and having relatively lower index of refraction than the peripheral annular region.

Abstract: An optical converter comprises: a first waveguide, a second waveguide, and a tapered waveguide arranged between both the waveguides, wherein heights of a core of the first waveguide and a core of the second waveguide are different; both ends in a direction of wave guiding of a core of the tapered waveguide are respectively connected to the core of the first waveguide and the core of the second waveguide; cross-sectional shapes and refractive indexes of cores of two waveguides that are connected change continuously or in a stepwise manner at each connection part; and a cross-sectional shape and refractive index of the core of the tapered waveguide change continuously or in a stepwise manner along a direction of wave guiding.

Abstract: Embodiments of an optical device, an array of optical devices, and a technique for fabricating the optical device or the array are described. This optical device is implemented on a substrate (such as silicon), and includes a thermally tunable optical waveguide that has good thermal isolation from its surroundings. In particular, a portion of a semiconductor in the optical device, which includes the optical waveguide, is free standing above a gap between the semiconductor layer and the substrate. By reducing the thermal coupling between the optical waveguide and the external environment, the optical device can be thermally tuned with significantly less power consumption.

Abstract: An optical device including a whispering gallery mode (WGM) optical resonator configured to support one or more whispering gallery modes; and a photodetector optically coupled to an exterior surface of the optical resonator to receive evanescent light from the optical resonator to detect light inside the optical resonator.

Abstract: Provided is a method for confirming optical fibers connection in a connection part in an optical connector, including: allowing light to pass through a first optical fiber and allowing cladding mode light to disappear; and detecting a difference in light intensity in the connection part between before and after the light from the first optical fiber enters a second optical fiber disposed in the optical connector.

Abstract: A waveguide and resonator are formed on a lower cladding of a thermo optic device, each having a formation height that is substantially equal. Thereafter, the formation height of the waveguide is attenuated. In this manner, the aspect ratio as between the waveguide and resonator in an area where the waveguide and resonator front or face one another decreases (in comparison to the prior art) thereby restoring the synchronicity between the waveguide and the grating and allowing higher bandwidth configurations to be used. The waveguide attenuation is achieved by photomasking and etching the waveguide after the resonator and waveguide are formed. In one embodiment the photomasking and etching is performed after deposition of the upper cladding. In another, it is performed before the deposition. Thermo optic devices, thermo optic packages and fiber optic systems having these waveguides are also taught.

Abstract: A double clad fiber includes a core, a first cladding provided so as to cover the core, and a second cladding provided so as to cover the first cladding. The second cladding has a plurality of pores extending in a length direction and arranged so as to surround the first cladding. In at least one fiber end, the second cladding has been removed by mechanical processing so that the at least one fiber end is formed by the core and the first cladding.

Abstract: A connection member (21), which electrically connects a package (14) on which an optical element that converts an electric signal to an optical signal or converts an optical signal to an electric signal and at least one end portion including an incident/releasing port for an optical signal of an optical waveguide (11) that is optically coupled with the optical element to transmit the optical signal are mounted, and a second substrate (2) to each other, is provided with a holding unit having elasticity, which holds the package (14), and a connection unit that is connected to the substrate (2).

Abstract: A micro-ring configured to selectively detect or modulate optical energy includes at least one annular optical cavity; at least two electrodes disposed about the optical cavity configured to generate an electrical field in the at least one optical cavity; and an optically active layer optically coupled to the at least one optical cavity. A method of manipulating optical energy within a waveguide includes optically coupling at least one annular optical cavity with the waveguide; and selectively controlling an electrical field in the at least one annular optical cavity to modulate optical energy from the waveguide.

Abstract: An apparatus includes a slider mounted on an arm, a first waveguide including a first core guiding layer, a second waveguide mounted on the slider and including a second core guiding layer having a uniform thickness smaller than the thickness of the first core guiding layer, and a coupler for coupling light from the first core guiding layer to the second core guiding layer, wherein the coupler comprises a curved mirror formed in the second waveguide and positioned to reflect light from the first core guiding layer into the second core guiding layer.

Abstract: A filter and fabrication process for a thin film filter that is based on frustrated total internal reflection and multiple waveguide layers, in which the waveguide modes are resonantly coupled. The physics of the design is related to prism coupling of light into planar waveguides, and waveguide coupling between planar waveguides in close proximity. Embodiments include a filter that acts as a bandpass filter and polarizer, a filter that acts as a bandpass filter, polarizer and angle filter (spatial filter), a filter that is widely tunable, and a filter that is widely tunable in both peak transmission wavelength and width. Methods of fabrication are disclosed, and methods to correct for manufacturing errors in thin film deposition are described. The filter embodiments can also be used in reflection as notch filters in wavelength and angle, for a particular polarization component.

Abstract: An integrated optical device is disclosed comprising a substrate, optical waveguide, and compound optical resonator having a temperature sensor, at least two coupled optical resonators, and a heater localized to each optical resonator. An optical input signal is coupled to one of the resonators making up the compound resonator to form an optical output signal. The center wavelength and shape of the output signal is optimized with a feedback loop using the temperature sensor to control the power dissipated in at least one of the localized heaters. The power dissipated in the remaining resonator heaters is set according to a predetermined function having as an input variable the power dissipated in the resonant heater under control of the said feedback loop.

Abstract: An electrically modulated plasmonic junction generates surface plasmons from an electrical signal from an electrical source, with the tunnel junction having a contact with a tapered end forming the junction in a gap between the contact and a substrate, with the gap serving to translate electrical signals into surface plasmons that are in turn translated into emitted photons communicated externally through a transmissive oxide, so that the junction can function as an electrically controlled light emitter preferably built as a nano-scale broadband optical emitter whose output wavelength can be electrically tuned over hundreds of nanometers, can be directly modulated at high speeds, and can have improved efficiencies compared to standard silicon optical sources, and the junction can also operate in a reserve mode for light detection.

Abstract: Exemplary methods of maximizing a spur-free dynamic range (SFDR) or a gain of an electro-absorption modulator (EAM) are disclosed. At least one parameter in a set of design parameters for an EAM is varied. An SFDR of the EAM is determined in part by a first set of design parameters. A gain of the EAM is determined in part by a second set of design parameters. An output versus bias voltage transfer curve of the EAM is generated. An optimal SFDR bias voltage at which a maximum SFDR occurs for a given optical input power or an optimal gain bias voltage at which a maximum gain occurs for a given optical input power is programmatically determined based at least in part on the transfer curve.

Abstract: Disclosed is an optical waveguide element that includes first and second optical waveguides (11, 12) which are formed to have different waveguide modes of guided lights, whose polarized waves are different. First optical waveguide (11) includes directional coupling region (13) and, second optical waveguide (12) includes incident side waveguide (12a), which has directional coupling region (13) and which is provided in parallel with first optical waveguide (11), and second optical waveguide (12) includes exit side waveguide (12b), which is extended from incident side waveguide (12a) and which is bent in the direction that recedes from first optical waveguide (11).

Abstract: An embodiment of the invention provides a coupled waveguide photo detector device. Optically, the device includes an input waveguide. An output waveguide is coupled to the input waveguide with a nonuniform coupling coefficient in a coupling section. An absorber is included in the coupling section to convert an absorbed portion of optical radiation into photo current. The location of absorber and the optical radiation intensity pattern in the coupling section are set to control the maximum intensity of output power absorbed by the output waveguide to be within a predetermined limit that avoids saturation. The absorber is also part of a transmission line collector which has a phase and group velocity to match those of the optical wave in the coupling section such that currents collected by the transmission line collector add in phase as the optical wave propagates in the output waveguide.

Abstract: An optical apparatus includes an optical resonator ring having at least one active region. The active region is configured to generate optical energy under an electrical stimulus. The optical apparatus also includes a corrugated plasmonic body disposed around at least a portion of the resonator ring and radiatively coupled to the active region.

Abstract: A waveguide and resonator are formed on a lower cladding of a thermo optic device, each having a formation height that is substantially equal. Thereafter, the formation height of the waveguide is attenuated. In this manner, the aspect ratio as between the waveguide and resonator in an area where the waveguide and resonator front or face one another decreases (in comparison to the prior art) thereby restoring the synchronicity between the waveguide and the grating and allowing higher bandwidth configurations to be used. The waveguide attenuation is achieved by photomasking and etching the waveguide after the resonator and waveguide are formed. In one embodiment the photomasking and etching is performed after deposition of the upper cladding. In another, it is performed before the deposition. Thermo optic devices, thermo optic packages and fiber optic systems having these waveguides are also taught.

Abstract: An optical connector having a plurality of directional taps and connecting between a plurality of optical waveguides (e.g., such as a connector between a waveguide that is part of, or leads from, a seed laser and/or an initial optical-gain-fiber power amplifier, and a waveguide that is part of, or leads to, an output optical-gain-fiber power amplifier and/or a delivery fiber), wherein one of the directional taps extracts a small amount of the forward-traveling optical output signal from the seed laser or initial power amplifier (wherein this forward-tapped signal is optionally monitored using a sensor for the forward-tapped signal), and wherein another of the directional taps extracts at least some of any backward-traveling optical signal that may have been reflected (wherein this backward-tapped signal is optionally monitored using a sensor for the backward-tapped signal).

Abstract: A nanoparticle array photonic waveguide, a photonic transmission system and a method of photonic transmission compensate for optical loss in an optical signal through stimulated emission using an optical gain material in a core of composite nanoparticles. The nanoparticle array photonic waveguide includes a plurality of the composite nanoparticles arranged adjacent to one another in a row. A composite nanoparticle of the plurality includes a shell and a core. The shell includes a negative dielectric constant material that is capable of supporting an optical signal on a surface of the shell. The core is adjacent to a side of the shell opposite to the shell surface. The core includes an optical gain material (OGM) that is capable of providing optical gain to the optical signal through stimulated emission within the OGM.

Abstract: An integrated optical device is disclosed comprising a substrate, optical waveguide, and compound optical resonator having a temperature sensor, at least two coupled optical resonators, and a heater localized to each optical resonator. An optical input signal is coupled to one of the resonators making up the compound resonator to form an optical output signal. The center wavelength and shape of the output signal is optimized with a feedback loop using the temperature sensor to control the power dissipated in at least one of the localized heaters. The power dissipated in the remaining resonator heaters is set according to a predetermined function having as an input variable the power dissipated in the resonant heater under control of the said feedback loop.

Abstract: Various embodiments of the present invention are directed to photonic interconnects that can be used for on-chip as well as off-chip communications between computer system components. In one embodiment of the present invention, a photonic interconnect comprises a plurality of on-chip waveguides. Additionally, the photonic interconnect may include a plurality of off-chip waveguides, and at least one optoelectronic converter. The at least one optoelectronic converter can be photonically coupled to a portion of the plurality of on-chip waveguides, can be photonically coupled to a portion of the plurality of off-chip waveguides, and is in electronic communication with at least one computer system component.

Abstract: A method comprises: (i) forming a first optical waveguide on a first substrate; (ii) forming a second, structurally discrete optical waveguide on a structurally discrete second substrate; (iii) assembling the second substrate or second optical waveguide with the first substrate or first optical waveguide so that the first and second optical waveguides are positioned between the first and second substrates and are relatively positioned for transferring the optical signal therebetween via optical transverse coupling; and (iv) arranging the first or second optical waveguide for transferring the optical signal therebetween via substantially adiabatic optical transverse coupling with the first and second waveguides so positioned.

Abstract: A connection member electrically connects an optical element configured to convert an electric signal to an optical signal or to convert an optical signal to an electric signal, a first substrate including an incident/releasing port of an optical transmission path for an optical signal at least one end portion thereof, and a second substrate to each other. The optical transmission path is optically coupled with the optical element to transmit the optical the connection. The connection member includes a connection unit connected to the second substrate and a holding unit having elasticity and holding the first substrate. The holding unit is provided with an electrode at a connecting position to the first substrate, and the holding unit holds the first substrate by connecting the first substrate to the electrode.

Abstract: A method comprises: forming an optical device on a device substrate; forming a first optical waveguide on the device or device substrate; forming a second, structurally discrete optical waveguide on a structurally discrete waveguide substrate; and assembling the optical device, first waveguide, or device substrate with the second waveguide or waveguide substrate. The device and first waveguide are arranged for transferring an optical signal between the device and the first waveguide. Upon assembly the first and second waveguides are positioned between the device and waveguide substrates and are relatively positioned for transferring the optical signal therebetween via optical transverse coupling. The first or second optical waveguide is arranged for transferring the optical signal therebetween via substantially adiabatic optical transverse coupling with the first and second waveguides so positioned.

Abstract: An active device for dynamic control of lightwave transmission properties has at least one photonic crystal waveguide that has anti-reflection photonic crystal waveguides with gradually changed group refractive indices at both input and output side. An alternating voltage or current signal applied to two electrically conductive regions changes the refractive indices of the photonic crystal materials, introducing a certain degree of blue-shift or red-shift of the transmission spectrum of the photonic crystal waveguide. The output lightwave with frequency close to the band-edge of the photonic crystal waveguide is controlled by the input electric signal. Devices having one or more such active photonic crystal waveguides may be utilized as an electro-optic modulator, an optical switch, or a tunable optical filter.

Abstract: Embodiments of an optical device, an array of optical devices, and a technique for fabricating the optical device or the array are described. This optical device is implemented on a substrate (such as silicon), and includes a thermally tunable optical waveguide that has good thermal isolation from its surroundings. In particular, a portion of a semiconductor in the optical device, which includes the optical waveguide, is free standing above a gap between the semiconductor layer and the substrate. By reducing the thermal coupling between the optical waveguide and the external environment, the optical device can be thermally tuned with significantly less power consumption.

Abstract: The present invention is directed to an evanescent field optical fiber device including one or more optical fibers and a support which assures mechanical strength of the optical fiber wherein one or more grooves has been machined in the support and in the coating of the one or more optical fiber in order to gain access to the evanescent field. The invention is also directed to the use of a support in the mechanical and chemical removal of coating from an optical fiber and a method of gaining access to the evanescent field of an optical fiber device.

Abstract: Apparatus, methods, and systems provide conversion of evanescent electromagnetic waves to non-evanescent electromagnetic waves and/or conversion of non-evanescent electromagnetic waves to evanescent electromagnetic waves. In some approaches the conversion includes propagation of electromagnetic waves within an indefinite electromagnetic medium, and the indefinite medium may include an artificially-structured material such as a layered structure or other metamaterial.

Abstract: Apparatus, methods, and systems provide conversion of evanescent electromagnetic waves to non-evanescent electromagnetic waves and/or conversion of non-evanescent electromagnetic waves to evanescent electromagnetic waves. In some approaches the conversion includes propagation of electromagnetic waves within an indefinite electromagnetic medium, and the indefinite medium may include an artificially-structured material such as a layered structure or other metamaterial.

Abstract: The waveguide in the ring and the bus waveguide in the immediate vicinity of the ring are made wider than the optimal single mode size. The bus waveguide has adiabatic tapers which serve to connect single mode portions in the bus waveguide to the wider portion of the bus waveguide to expand the mode from the narrower waveguide to the wider waveguide. Since the light is now spread out over a larger area in the wider waveguides, the scattering loss from the sidewalls is reduced and the loss is lower. This lower loss gives rise to a higher Q in the ring since the Q of the ring is directly proportional to the round trip loss.

Abstract: An optical component including an acceptance fiber, e.g. a photonic crystal fiber, for propagation of pump and signal light, a number of pump delivery fibers and a reflector element that reflects pump light from the pump delivery fibers into the acceptance fiber. An optical component includes a) a first fiber having a pump core with an NA1, and a first fiber end; b) a number of second fibers surrounding the pump core of the first fiber, at least one of the second fibers has a pump core with an NA2 that is smaller than NA1, the number of second fibers each having a second fiber end; and c) a reflector element having an end-facet with a predetermined profile for reflecting light from at least one of the second fiber ends into the pump core of the first fiber.

Abstract: In an embodiment, light from a single mode light source may be deflected into a low index contrast (LIC) waveguide in an opto-electronic integrated circuit (OEIC) (or “opto-electronic chip”) by a 45 degree mirror. The mirror may be formed by polishing an edge of the die at a 45 degree angle and coating the polished edge with a metal layer. Light coupled into the LIC waveguide may then be transferred from the LIC waveguide to a high index contrast (HIC) waveguide by evanescent coupling.

Abstract: An electrooptically tunable waveguide-coupled microresonator. In one example embodiment, the switch includes a photoalignment layer that enhances control of liquid crystal alignment in the cladding near the coupling region of the microresonator and waveguide.

Abstract: Discrete first and second optical transmission subunits are formed each having a corresponding transmission optical waveguide with a corresponding optical junction region. The first transmission optical waveguide is a planar optical waveguide formed on a substrate. The first transmission optical waveguide or the second transmission optical waveguide is adapted for enabling substantially adiabatic transverse-transfer of optical power between the optical waveguides at the respective optical junction regions. The first and second optical transmission subunits are assembled together to form an optical apparatus.

Abstract: A reflective display having a plurality of transparent hemi-beads (120), each having a reflective region (80) surrounding a non-reflective region (82). Each hemi-bead has an associated light absorptive fluid droplet (122) having a normally relaxed shape contacting the non-reflective region, thereby frustrating total internal reflection of light rays at the droplet/hemi-bead interface. An electrical potential is selectably applied across selected droplets. Application of the electrical potential across a droplet deforms the droplet away from the hemi-bead associated with the droplet, such that light rays (158) incident on the non-reflective region are refracted toward substrate (124) and reflected back through hemi-bead (120) in an approximately opposite direction (166); and such that light rays (162) incident on the reflective region are semi-retro-reflected (168). Removal of the electrical potential allows the droplet to resume the relaxed shape.

Abstract: An optical waveguide device (10) comprises a planar substrate with a lower cladding layer (14), a core layer (16) and an upper cladding layer (18), a groove (20) in the substrate that extends at least into the core layer (16), and a waveguiding channel (22) in the core layer (16), wherein at least a part of the waveguiding channel (22), which may contain a Bragg grating, is sufficiently proximate to the groove (20) in the plane of the substrate for an evanescent field of light propagating in the waveguiding channel (22) to extend laterally into the groove (20). Material contained in the groove modifies the properties of the waveguiding channel, so that a sample of material can be analysed or an active material can be used to modulate the propagating light. The groove (20) can be made before the waveguide (22). The groove (20) can be made by cutting into the substrate with a saw and the waveguide (22) can be made by direct writing in the core layer (16) with an ultraviolet beam.

Abstract: A micro-ring configured to selectively detect or modulate optical energy includes at least one annular optical cavity; at least two electrodes disposed about the optical cavity configured to generate an electrical field in the at least one optical cavity; and an optically active layer optically coupled to the at least one optical cavity. A method of manipulating optical energy within a waveguide includes optically coupling at least one annular optical cavity with the waveguide; and selectively controlling an electrical field in the at least one annular optical cavity to modulate optical energy from the waveguide.

Abstract: Method and apparatus enable optical evanescent sensing utilizing a waveguide with an annular core. The annular core can provide detectable sensitivity to a measurand due to optical interactions with contents along an inside surface of the annular core since optical properties of the contents vary with changes in the measurand.

Abstract: A semiconductor laser comprises two optical ring resonators, each comprising an optical waveguide electrically pumped to provide optical gain. The two ring resonators have different round-trip optical path lengths, and are coupled to each other through a half-wave optical coupler. The half-wave optical coupler has a predetermined cross-coupling coefficient and a 180-degree cross-coupling phase. The cross-coupling coefficient is substantially less than the self-coupling coefficients in order to achieve an optimal single-mode selectivity of the laser. The first ring resonator has an optical path length such that its resonant wavelengths correspond to a set of discrete operating channels. The second ring resonator has a slightly different length so that only one resonant wavelength coincides with one of the resonant wavelengths of the first ring resonator over the operating spectral window. The lasing action occurs at the common resonant wavelength.

Abstract: Disclosed is a fiber amplifier system including a gain fiber having a single-mode core containing dopant ions capable of producing stimulated emission of light at wavelength ?s when pumped with light of wavelength ?p. Absorbing ion filtering means is operatively associated with the gain fiber to alter the gain curve. If the absorbing ions are the same as the gain ions of the gain fiber, the system further includes means for preventing pump light from exciting the gain ions of the filtering means. The excitation prevention means may take the form of means for attenuating pump light. If the absorbing ions are different from the dopant ions of the gain fiber, such absorbing ions can be subjected to light at wavelength ?p, but they will remain unexcited. Such absorbing ions can be used to co-dope the gain fiber, or they can be incorporated into the core of a fiber that is in series with the gain fiber.