Abstract: An optical signal processing device includes a waveform width widening unit configured to widen a waveform width of an optical signal; and an optical limiter circuit, to which the optical signal the waveform width of which is widened is input, configured to suppress an intensity of the optical signal in a region where an input intensity and an output intensity are not proportional.

Abstract: A periodically poled optical waveguide comprising a nonlinear optical crystalline material is provided having poled optical domains slanted with respect to direction of propagation of light within the waveguide. Light reflected from slanted poled optical domains does not couple efficiently back into the optical waveguide, which facilitates reduction of backreflection towards a semiconductor laser source coupled to the waveguide. Reduction of backreflections facilitates stable operation of the semiconductor laser source. A method of manufacturing of a periodically poled optical waveguide with slanted poled domains is also provided.

Abstract: A multimode fiber including a core and a cladding. The core has a radius (R1) of 24-26 ?m, the refractive index profile thereof is a parabola, and the maximum relative refractive index difference (?1) is 0.9-1.1%. The cladding surrounds the core and includes from inside to outside an inner cladding, a middle cladding, and an outer cladding; a radius (R2) of the inner cladding is 1.04-1.6 times that of the core, and a relative refractive index difference (?2) thereof is ?0.01-0.01%; the middle cladding is a graded refractive index cladding whose radius (R3) is 1.06-1.8 times that of the core, and a relative refractive index difference thereof is decreased from ?2 to ?4; and a radius (R4) of the outer cladding is 2.38-2.63 times that of the core, and a relative refractive index difference (?4) thereof is between ?0.20 and ?0.40%.

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: Frequency standards based on mode-locked fiber lasers, fiber amplifiers and fiber-based ultra-broad bandwidth light sources, and applications of the same.

Abstract: Optical pulse compressor having a chirp unit including a normal dispersion fiber that provides a positive chirp to an input pulse and having a dispersion compensator including an anomalous fiber is provided. The nonlinear coefficient and the absolute value of the second-order group-velocity dispersion of the anomalous fiber that forms the dispersion compensator is set such that a soliton order becomes one or more, and the fiber length of the anomalous dispersion fiber is made to be equal to or smaller than a length required for optical soliton formation.

Abstract: Frequency standards based on mode-locked fiber lasers, fiber amplifiers and fiber-based ultra-broad bandwidth light sources, and applications of the same.

Abstract: Plasmons on a waveguide may deliver energy to photocatalyze a reaction. The waveguide or other energy carrier may be configured to carry electromagnetic energy and generate plasmon energy at one or more locations proximate to the waveguide, where the plasmon energy may react chemically with a medium or interaction material.

Abstract: A new nonlinear optical structure for frequency conversion is described. The new nonlinear optical structure is a multilayer wafer comprising alternating layers of gallium arsenide and aluminum gallium arsenide onto a gallium arsenide substrate. The new device is both more efficient and easier to make than prior art gallium arsenide crystal structures designed for nonlinear optical conversion.

Abstract: Systems and methods are disclosed to process an optical signal using a pre-processor to populate a non-linearity compensation data structure based on a set of predetermined rules in a non-real-time off-line mode; and an amplifier applying said predetermined rules in real-time to one or more channel input data using the data structure to determine a non-linearity compensation output.

Abstract: The disclosure relates to an optical fiber including a core and a cladding having a core material and a cladding material, respectively, wherein the fiber is a non-linear microstructured optical fiber, the microstructured optical fiber being obtainable by a method including loading the core material and optionally the cladding material with hydrogen and/or deuterium whereby the lifetime of the fiber may be extended in high pulse applications.

Abstract: The present invention relates to an optical communications system that allows improving OSNR while suppressing the power increase of pumping light for distributed Raman amplification. In the optical communications system, an optical fiber is laid in a transmission section between a transmitter station (or repeater station) and a receiver station (or repeater station), and optical signals are transmitted from the transmitter station to the receiver station via the optical fiber. In the optical communications system, pumping light for Raman amplification, outputted by a pumping light source provided in the receiver station, is fed into the optical fiber via an optical coupler, and the optical signals are distributed-Raman-amplified in the optical fiber. The transmission loss and the effective area of the optical fiber satisfy, at the wavelength of 1550 nm, a predetermined relationship.

Abstract: A microstructured optical fiber for transmitting optical signals comprised of light, the optical fiber comprising: a core region disposed about a longitudinal centerline and having a refractive index profile with a first refractive index, and a cladding region surrounding the core region, the cladding region comprising an annular void-containing region comprised of non-periodically disposed voids; wherein maximum void diameter in nm is given by Dmax and the maximum void length in cm is not greater than 2.5×105×(dmax)?1.7.

Abstract: An apparatus and method for producing optical pulses of a desired wavelength utilizes a section of higher-order-mode (HOM) fiber to receive input optical pulses at a first wavelength, and thereafter produce output optical pulses at the desired wavelength through soliton self-frequency shifting (SSFS) or Cherenkov radiation. The HOM fiber is configured to exhibit a large positive dispersion and effective area at wavelengths less than 1300 nm.

Abstract: A two-dimensional photonic crystal according to the present invention includes a first layer having a dielectric first layer slab in which first layer holes having a refractive index lower than that of the first layer slab are arranged cyclically, a second layer formed on the first layer, including dielectric columns having a refractive index higher than the air arranged in the air with the same cycle as the first layer hole, and a third layer having a dielectric third layer slab in which third layer holes having a refractive index lower than that of the third layer slab are arranged cyclically. Thus, it is possible to obtain the two-dimensional photonic crystal that can create a wider complete PBG than before regardless of the polarization of light and can be manufactured easily.

Abstract: An optical fiber connection structure which reduces MPI in the use of an optical fiber with a bend resistance improved by forming holes in the fiber, and a single-mode fiber which reduces MPI are provided. A second cladding portion of a second single-mode fiber 20 includes holes 28, and thus, the second single-mode fiber 20 has low bending loss. A portion of the second single-mode fiber 20 connected to a first single-mode fiber 10a is made solid by filling corresponding portions of the holes 28 over the length L0, and light in a mode LP11 is significantly attenuated in this portion, thereby reducing MPI.

Abstract: Adhesive-free bond non-linear optical (NLO) components, devices and systems including one or more engineered quasi non-critical phase matched or contra-phase matched NLO crystal doublets. Such systems and devices advantageously increase the efficiency of NLO frequency conversion and improve beam quality. Devices are applicable to any uniaxial and biaxial NLO crystals in a wide range of wavelengths, e.g., from far ultraviolet to visible to far infrared. Devices employing engineered AFB NLO components according to certain embodiments include any conventional frequency converting architectures. Systems and methods are also provided to unambiguously determine and correct walk-off for any arbitrary uniaxial and biaxial crystal orientation.

Abstract: A method is provided for predicting an installed performance parameter of an optical fiber cable. The method includes obtaining a measurement indicative of a value of the performance parameter at a first moment in time. A measurement indicative of a value of the performance parameter at a second moment in time may then be obtained. A first correlation may then be determined between the measurement at the first moment in time and the measurement at the second moment in time. A value of the performance parameter at the second moment in time may then be estimated based upon the measurement at the first moment in time in combination with the first correlation, the first correlation being based upon observations of a manner in which the performance parameter varies over time for at least a second optical fiber.

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: An optical fiber includes a cladding, a first core, and a second core. At least one of the first core and the second core is hollow and is substantially surrounded by the cladding. At least a portion of the first core is generally parallel to and spaced from at least a portion of the second core. The optical fiber includes a defect substantially surrounded by the cladding, the defect increasing a coupling coefficient between the first core and the second core.

Abstract: Provided is an optical fiber that has a small bending loss, can be securely prevented from being fractured due to accidental bending during installation or other operations, and is compliant with the G. 652 standard. An optical fiber 1 includes a core 11, a first cladding 12, a second cladding 13, and a third cladding 14. The relative refractive index difference ?1 of the core 11 is in the range of 0.3% to 0.38%, the relative refractive index difference ?2 of the first cladding 12 is equal to or smaller than 0%, and the relative refractive index difference ?3 of the second cladding 13 is in the range of ?1.8% to ?0.5%. The inner radius r2 and the outer radius r3 of the second cladding 13 satisfy the expression “0.4r2+10.5<r3<0.2r2+16”, and the inner radius r2 of the second cladding 13 is equal to or greater than 8 ?m. The bending loss at a wavelength of 1550 nm and at a radius of curvature of 7.5 mm is smaller than 0.

Abstract: An optical assembly includes a gas cell and an optical fiber portion in which the gas cell is contiguously attached to the optical fiber portion. The gas cell can be made, for example from hollow-core photonic crystal fiber (HC-PCF).

Abstract: Provided is an optical fiber that has a small bending loss, can be securely prevented from being fractured due to accidental bending during installation or other operations, and is compliant with the G. 652 standard. An optical fiber 1 includes a core 11, a first cladding 12, a second cladding 13, and a third cladding 14. The relative refractive index difference ?1 of the core 11 is in the range of 0.3% to 0.38%, the relative refractive index difference ?2 of the first cladding 12 is equal to or smaller than 0%, and the relative refractive index difference ?3 of the second cladding 13 is in the range of ?1.8% to ?0.5%. The inner radius r2 and the outer radius r3 of the second cladding 13 satisfy the expression “0.4r2+10.5<r3<0.2r2+16”, and the inner radius r2 of the second cladding 13 is equal to or greater than 8 ?m. The bending loss at a wavelength of 1550 nm and at a radius of curvature of 7.5 mm is smaller than 0.

Abstract: Provided is a multi-cladding optical fiber which includes: a core with an average refractive index n1; and a cladding including an inner cladding with an average refractive index n2 formed on the periphery of the core, an intermediate cladding with an average refractive index n3 formed on the periphery of the inner cladding, and an outer cladding with an average refractive index n4 formed on the periphery of the intermediate cladding where n1>n2>n3>n4. Two or more axisymmetric modes exist in the core at a wavelength of the signal light; the two or more axisymmetric modes including a fundamental mode and at least a high-order mode. When the fiber is bent at a predetermined bending diameter, the high-order mode in the core disperses within the inner cladding due to coupling with an inner cladding mode, so that only the fundamental mode substantially propagates through the core.

Abstract: Since the magnitude of a nonlinear effect depends on the nonlinearity coefficient of the microstructured fiber and the intensity of pump light, either the nonlinearity coefficient or the intensity of pump light are adjusted. The nonlinearity coefficient is modified by introducing a nonlinear refractive index profile that has the inverse characteristic of the intensity distribution of either the pump or the signal light. The intensity of the pump light is adjusted by an optical amplifier, an optical attenuator, or a pre-emphasizing filter under the control of a control unit. The control unit controls the intensity of the pump light based on a look-up table which is prepared in advance by experiment or calculation, or based on a function of the pump and signal wavelength.

Abstract: A multimode optical fiber has an equivalent modal dispersion value (DMDinner&outer) of less than 0.11 ps/m for (??max×D)>0.07 ps/m as measured on a modified DMD graph. The modified DMD graph accounts for chromatic dispersion to ensure that the multimode optical fiber has a calculated effective bandwidth EBc greater than 6000 MHz-km when used with multimode transverse sources.

Abstract: A lumenaire for mixing and emitting light from multiple light sources which has at least one first light source of a particular type and at least one second light source of a differing type. There is an optical system which includes at least one individual light collecting optical element at least partially surrounding each light source. There is a substantially planar light guide that receives and transports the light from each of the individual optical elements and optically mixes and emanates the light from both types of light sources simultaneously, through a common surface of the planar light guide. The planar light guide is segmented and the segmented sections are angularly disposed, in section in relationship to each other and the individual optical elements project light into at least one of the segments.

Abstract: An optical element is disclosed which includes transparent superconductor material.

Abstract: A new deep blue extended super continuum light source is provided wherein said super continuum at least extends to a low wavelength border ?low low below 480 nm comprising a pump source which operates at a at least one wavelength ?pump and produces pump pulses of a duration (full width half maximum) longer than 0.1 picoseconds with a repetition rate higher than 1 MHz, and a peak power ?peak, and a micro-structured optical transmission medium having at least one wavelength of zero dispersion ?zero, and for the parameters for said pump source exhibiting a second order dispersion parameter ?2, and a non-linear parameter ? arranged so that the optical transmission medium exhibits a modulation instability gain extending to wavelengths above a wavelength ?high?1300 nm and a phase match between ?1ow and a wavelength ?match??high, wherein the pump is adapted to provide energy within the region of anomalous dispersion of the transmission medium.

Abstract: A process for poling a ferroelectric material doped with a metal, which process comprises: (i) defining an electrode pattern on a ?z face of a crystal of the ferroelectric material doped with the metal; (ii) providing an electrode material; (iii) poling at a temperature of not more than 45° C.; and (iv) poling by a two-stage voltage-controlled application of electric field based on a first poling stage of domain nucleation and a second poling stage of domain spreading.

Abstract: This invention relates generally to the field of quasicrystalline structures. In preferred embodiments, the stopgap structure is more spherically symmetric than periodic structures facilitating the formation of stopgaps in nearly all directions because of higher rotational symmetries. More particularly, the invention relates to the use of quasicrystalline structures for optical, mechanical, electrical and magnetic purposes. In some embodiments, the invention relates to manipulating, controlling, modulating and directing waves including electromagnetic, sound, spin, and surface waves, for a pre-selected range of wavelengths propagating in multiple directions.

Abstract: In a blue extended super continuum light source, when pulses of partly coherent monochromatic “pump” radiation of essentially constant amplitude are propagating through a microstructure fiber medium within a region of anomalous dispersion of the medium, then, provided the medium has a finite nonlinear coefficient of the index of refraction, the pump pulse is subject to a modulation instability. This results in formation of a train of narrow pulses with Tera Hertz repetition rate. Phase match between red shifted Raman solitons generated by the pump pulse and energy shed by the pump pulse at all frequencies with a group velocity below the pump pulse group velocity may lead to the formation of Cherenkov radiation. The solitons may seed Cherenkov radiation at different wavelengths depending on the actual fiber parameters. This allows extension of generated super continuum light beyond the four wave mixing limit when applying picosecond or nanosecond pump pulses.

Abstract: Photonic detection systems and methods are shown. A flow through photonic membrane is provided with pores which are distributed along multiple regions. The pores of one region have walls to which a first type of target specific anchor can be attached, while pores of another region have walls to which a second type of target specific anchor can be attached. An additional region of pores without anchors can be provided, so that optical detection occurs differentially. A stack of photonic membranes is also provided. The diameter of the pores of one photonic membrane is larger than the diameter of the pores of another photonic membrane, thus allowing also determination of the size of a target organism flown through the stack of membranes.

Abstract: A broadband light source includes one or more laser diodes that are capable of generating a pump signal having a wavelength shorter than 2.5 microns, a pulse width of at least 100 picoseconds and a pump optical spectral width. The light source also includes one or more optical amplifiers that are coupled to the pump signal and are capable of amplifying the pump signal to a peak power of at least 500 W. The light source further includes a first fiber that is coupled to the one or more optical amplifiers. The first fiber including an anomalous group-velocity dispersion regime and a modulational instability mechanism that operates to modulate the pump signal. In one particular embodiment, the pump signal wavelength resides in the anomalous group-velocity dispersion regime of the first fiber and where different intensities in the pump signal can cause relative motion between different parts of the modulated pump signal produced through modulational instability in the first fiber.

Abstract: A method of inducing a periodic variation of nonlinearity value in a sample of ferroelectric material comprises arranging a pair of electrodes on opposite faces of the sample, one electrode defining a desired pattern of nonlinearity variation, applying a pre-bias voltage across the sample for a predetermined time using the electrodes, the pre-bias voltage being less than the coercive field of the ferroelectric material; and after the predetermined time, applying a current-controlled poling voltage across the sample using the electrodes, to produce domain inversion in the sample according to the desired pattern of nonlinearity variation. The pre-bias voltage may be 75% of the coercive field or more, and applied for a pre-determined time between 1 and 100 seconds.

Abstract: An optical communications link is described, comprising first and second fiber lines in substantial scaled translational symmetry by a common scaling factor with respect to a second-order dispersion coefficient profile (oppositely signed) and with respect to at least one of a loss/gain coefficient profile and a nonlinear coefficient-power product profile for facilitating progressive compensation along the second fiber line of at least one nonlinearity introduced along the first fiber line. For other described embodiments, the first and second fiber lines are in substantial scaled translational symmetry by a common scaling factor with respect to a second-order dispersion coefficient profile and with respect to at least one of a loss/gain coefficient profile and a nonlinear coefficient-power product profile for facilitating progressive compensation along the second fiber line of at least one nonlinearity introduced along the first fiber line.

Abstract: An optical signal processing device has nonlinear optical medium, first and second power controllers, and polarization controllers. To the nonlinear optical medium, signal light, and first and second pumping lights having wavelengths different from the signal light are input. The first and the second power controllers are provided at the input side of the nonlinear optical medium, and control the powers of the first and the second pumping lights so that a predetermined gain is obtained in the nonlinear optical medium. The polarization controllers are provided at the input side of the nonlinear optical medium, and adjust the first and the second pumping lights so that the polarization states of the first and the second pumping lights are mutually orthogonal.

Abstract: The present invention is directed towards systems and methods for adjusting intensity, wavelength and higher and lower frequency components of an optical signal. Photonic apparatus receives a first and a second optical signal. A waveguide provides an anomalous group velocity dispersion the first optical signal or the second optical signal and adjusts intensity or wavelength of the first optical signal or the second optical signal, in response to the anomalous group velocity dispersion. In some embodiments photonic apparatus receives an optical signal comprising a lower frequency component received an amount of time prior to a higher frequency component of the optical signal. A waveguide provides an anomalous group velocity dispersion for the optical signal and adjusts the amount of time between the higher frequency component and the lower frequency component in response to the anomalous group velocity dispersion.

Abstract: A photonic bandgap fiber includes a core and a cladding that surrounds the core. In this photonic bandgap fiber, high refractive index portions which have a refractive index higher than that of a medium of the cladding are provided in the cladding so as to form a triangular lattice structure with a lattice constant ?, and the refractive index of the core is higher than the refractive index of the medium of the cladding and lower than the refractive index of the high refractive index portion. The coupling length between the core and the high refractive index portion that is closest to the core is longer than the coupling length between adjacent high refractive index portions, or a periodic structure formed by the high refractive index portions is not provided around the entirely of the area along the circumference of the core.

Abstract: The present invention relates to a frequency shifter in an optical path containing a pulsed laser source, and it is characterized in that it comprises at least one frequency shifter (12, 13) containing an optical propagation medium, the optical path length of which is modified according to the desired frequency shift during at least one pulse among n consecutive pulses from the laser, where n?1.

Abstract: A non-linear optical device includes a frequency-conversion waveguide and first and second input waveguides. The longitudinal axes of the input waveguides are inclined to that of the frequency-conversion waveguide such a first transverse mode is excited in the latter at the input frequency in operation of the device. The frequency-conversion waveguide supports a second transverse mode at an output frequency of the device, such that the phase velocity of the second transverse mode at the output frequency is substantially equal to that of the first transverse mode at the input frequency, thus providing phase-matching by balancing the effects of chromatic and modal dispersion.

Abstract: In accordance with the present invention, a bulk optic material (for example, silica) is processed to form a spatially microstructured element, such as a photonic bandgap (PBG) structure. An ultra-short laser pulse source is used as an input signal that is applied to the bulk optic PBG structure to generate an enhanced continuum output. The PBG structure may comprise any type of one-, two- or three-dimensional grating structure, where the selected structure will dictate the type(s) of enhancement(s) that are present in the generated continuum—generally in the form of a broadened continuum and/or the inclusion of one or peaks in the continuum. The use of a relatively small-dimensioned bulk material allows for the continuum to be generated without the need for any type of optical confinement (waveguide). In one embodiment, the bulk PBG structure may be is subjected to one or more additional processes (such as UV exposure, electromagnetic field application, etc.

Abstract: The invention relates to a photonic crystal circuit comprising a guide produced in a photonic crystal membrane on the surface of a substrate and a mode adapter coupled to said guide, wherein the membrane includes a central point constituting the mode adapter having a section gradient as termination of said guide, said point being suspended so as to allow the propagation of modes in a symmetrical manner. It also relates to an optical system incorporating said circuit coupled to an optical fiber.

Abstract: There is described an optical waveguide structure exhibiting nonlinear properties, a method of fabricating such, and an optical coupling device made of two of such optical waveguide structures. The optical waveguide structure comprises an optical waveguide portion made of a light transmitting material for supporting a light mode traveling therein. The light transmitting material has an intrinsic nonlinearity parameter suitable for inducing a nonlinearity on the light mode, and the optical waveguide portion having a diameter sized to securely confine the light mode therein and to increase the nonlinearity on the light mode. The optical waveguide structure also has a coating surrounding the optical waveguide portion to mechanically support or to protect the optical waveguide portion from surface damage.

Abstract: A phase modulation waveguide structure includes one of a semiconductor and a semiconductor-on-insulator substrate, a doped semiconductor layer formed over the one of a semiconductor and a semiconductor-on-insulator substrate, the doped semiconductor portion including a waveguide rib protruding from a surface thereof not in contact with the one of a semiconductor and a semiconductor-on-insulator substrate, and an electrical contact on top of the waveguide rib. The electrical contact is formed of a material with an optical refractive index close to that of a surrounding oxide layer that surrounds the waveguide rib and the electrical contact and lower than the optical refractive index of the doped semiconductor layer. During propagation of an optical mode within the waveguide structure, the electrical contact isolates the optical mode between the doped semiconductor layer and a metal electrode contact on top of the electrical contact.

Abstract: A 1.55 ?m band dispersion shifted optical fiber is provided which has a low loss and low dispersion slope. A core region “a” is heavily doped with GeO2 . A core region “b” is composed of pure SiO2 glass. A cladding section is arranged around the core region. The cladding section has a lot of holes extending in the longitudinal direction of the optical fiber. The holes of the cladding section are not located at random, but have a honeycomb structure composed of regular hexagons which have a side length of ?, and serve as a primitive lattice. The center of the core section has a region having a refractive index higher than that of the periphery of the core section. The core section has the refractive index distribution in which the group velocity dispersion at the operation wavelength of the region becomes the normal dispersion.

Abstract: A frequency-conversion method that uses a nonlinear optical process to transfer energy between a surface-plasmon (SP) wave that is guided along an electrically conducting strip and a light beam that is guided along an optical waveguide whose core is adjacent to the electrically conducting strip. A periodic structure spatially modulates the nonlinear susceptibility of the waveguide core with a spatial period that is related to a momentum mismatch in the nonlinear optical process. The spatial modulation provides quasi-phase matching for the SP wave and the light beam and enables efficient energy transfer between them.

Abstract: A method of modifying light is disclosed and includes: providing an optical element having an oriented polymer network of a silicone (meth)acrylate copolymer and exhibiting a first phase and a second phase, the first phase and the second phase being chemically connected and having different refractive indices, the first phase being continuous, and the second phase comprising a plurality of structures dispersed within the first phase; illuminating the optical element with light from a light source; and detecting polarized or directionally diffused light transmitted by the optical element. Optical elements including the polymer network and a variety of additional layers are also disclosed, as are optical devices such as prisms, display panels, lenses, and the like.

Abstract: Affords a wavelength converter manufacturing method and a wavelength converter whereby the transmissivity can be improved. A method of manufacturing a wavelength converter (10a) is provided with the following steps. At first, crystal is grown. Then a first crystal (11) and a second crystal (12) are formed by sectioning the crystal into two or more in such a way that the domains are the reverse of each other. The first and second crystals (11) and (12) are then interlocked in such a way that a domain inversion structure in which the polar directions of the first and second crystals (11) and (12) periodically reverse along an optical waveguide (13) is formed, and the domain inversion structure satisfies quasi-phase-matching conditions for an incoming beam (101).

Abstract: A multimode optical fiber has an equivalent modal dispersion value (DMDinner&outer) of less than 0.11 ps/m for (??max×D)>0.07 ps/m as measured on a modified DMD graph. The modified DMD graph accounts for chromatic dispersion to ensure that the multimode optical fiber has a calculated effective bandwidth EBc greater than 6000 MHz-km when used with multimode transverse sources.