WO2014030578A1 - Élément à guides d'ondes optiques - Google Patents

Élément à guides d'ondes optiques Download PDF

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Publication number
WO2014030578A1
WO2014030578A1 PCT/JP2013/071868 JP2013071868W WO2014030578A1 WO 2014030578 A1 WO2014030578 A1 WO 2014030578A1 JP 2013071868 W JP2013071868 W JP 2013071868W WO 2014030578 A1 WO2014030578 A1 WO 2014030578A1
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Prior art keywords
waveguide
sub
optical
main
mode
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PCT/JP2013/071868
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English (en)
Japanese (ja)
Inventor
裕幸 日下
憲介 小川
一宏 五井
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株式会社フジクラ
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Publication of WO2014030578A1 publication Critical patent/WO2014030578A1/fr

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G02B6/122—Basic optical elements, e.g. light-guiding paths
    • G02B6/125—Bends, branchings or intersections
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/2804—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers

Definitions

  • the present invention relates to an optical multiplexer and an optical waveguide device including a mode splitter.
  • the present invention also relates to an optical waveguide device including a mode splitter.
  • the other modes are called n-order modes corresponding to the number of modes n.
  • modes of n ⁇ 1 are collectively referred to as higher order modes.
  • Si optical waveguides having silica (SiO 2 ) as a cladding and silicon (Si) as a core can be miniaturized using a high refractive index difference (Si / SiO 2 ), and Si -It is attracting attention and expectation because it can be manufactured relatively inexpensively using existing manufacturing equipment for LSIs (Large Scale Integrated Circuits).
  • an optical multiplexer such as a multi-mode interferometer (MMI) type multiplexer or a Y-type multiplexer is often incorporated in the configuration.
  • MMI multi-mode interferometer
  • a Mach-Zehnder Interferometer (MZI) optical modulator controls switching of an optical signal between an on state and an off state based on a phase difference between two lights injected into the optical multiplexer.
  • MZI Mach-Zehnder Interferometer
  • the width of the waveguide is appropriately selected so that the primary mode light of the combined light does not propagate through the optical waveguide downstream of the optical multiplexer, so that only the fundamental mode light propagates through the waveguide. I have to.
  • Patent Document 1 there is a conventional technique in which primary mode light propagating through a main waveguide is separated by adiabatic transition into a sub-waveguide having a tapered structure along the main waveguide, guided, and removed from the main waveguide.
  • Non-Patent Document 1 As a prior art regarding Si / SiO 2 waveguide, Non-Patent Document 1 (2.2, 3.2, FIG. 1, FIG. 4, etc.) has two thicknesses of 200 nm, a width of 400 nm, and an interval of 480 nm.
  • a polarization mode separator (PS) using a directional coupler (DC) formed of a Si waveguide can separate polarization modes in a length of about 10 ⁇ m. It is disclosed.
  • the relative refractive index difference of the Si / SiO 2 waveguide is very large, about 40% or more, compared to about 0.1 to several percent, which is the relative refractive index difference of the silica-based waveguide.
  • the core width needs to be 450 nm or less.
  • the waveguide loss is about 0.16 dB / mm when the core width is 500 nm, whereas the waveguide loss is about 0.40 dB / mm when the core width is 400 nm.
  • the waveguide loss when the core width is 400 nm is about 2.5 times the waveguide loss when the core width is 500 nm. That is, the narrower the core width, the higher the waveguide loss, and the easier the waveguide characteristics to deteriorate due to the surface roughness.
  • the taper structure described in Patent Document 1 is adopted. Virtually impossible.
  • a gentle taper portion is required. Referring to the simulation disclosed in Chapter 4 of Non-Patent Document 2, the length of the branch portion necessary for the first-order mode branch by the adiabatic transition is about 1000 ⁇ with the wavelength ⁇ as a unit. If the wavelength of incident light is 1.55 ⁇ m, the length of the tapered portion is required to be about 1.5 mm.
  • Example 1 of Patent Document 1 it is disclosed that a taper length of 2 mm is necessary for a wavelength of incident light of 1.5 ⁇ m.
  • a device having a large relative refractive index difference such as a Si / SiO 2 waveguide has a great advantage in downsizing an optical device using a device of ⁇ m order using a high refractive index difference. It is not possible to incorporate a device having a size of mm.
  • Patent Document 1 since the fundamental mode light and the first-order mode light are separated by adiabatic transition, the distance between the two waveguides needs to be extremely small with respect to the waveguide width.
  • Non-Patent Document 1 discloses a device capable of separating polarization modes, but a device capable of separating propagation modes having different mode numbers n (for example, separation between a fundamental mode and a higher-order mode). Is not disclosed.
  • an object of the present invention is to provide an optical waveguide device including a mode splitter capable of mode separation.
  • An optical waveguide device is an optical multiplexer that multiplexes a plurality of input lights into one output light, and guides the input light and the output light to propagate at least two or more types.
  • a main waveguide capable of guiding propagation modes of different orders, and a coupling portion arranged in parallel to the main waveguide at a certain distance from the main waveguide so as to form a directional coupler; and
  • the difference between the width of the main waveguide and the width of the sub waveguide in the directional coupler may be within ⁇ 10%.
  • the difference between the thickness of the main waveguide and the thickness of the sub waveguide in the directional coupler may be within ⁇ 10%.
  • the sub-waveguide may further include a start portion that is continuous with the front end portion of the coupling portion, and may gradually approach the main waveguide as the start portion approaches the front end portion.
  • the sub-waveguide may further include an end portion that is continuous with an end portion at the rear stage of the coupling portion, and may gradually move away from the main waveguide as the end portion moves away from the end portion at the rear stage.
  • the mode splitter may be provided in the optical waveguide that guides the output light.
  • the optical multiplexer and the mode splitter may be continuously provided in a cascade type.
  • the optical waveguide device further includes an optical demultiplexer that demultiplexes one input light into two demultiplexed lights, and an optical modulator, and the optical multiplexer converts the two demultiplexed lights into one output light.
  • One of the two demultiplexed lights is input to the optical multiplexer via the optical modulator, and the other demultiplexed light of the two demultiplexed lights does not pass through the optical modulator. May be input to the optical multiplexer.
  • the optical waveguide element includes a plurality of the mode splitters, and a difference between the width of the main waveguide and the width of the sub waveguide in each directional coupler is within ⁇ 10%, The distance between the coupling portion and the main waveguide and the length of the coupling portion of the sub waveguide may be equal among all the directional couplers. A difference between the width of the main waveguide and the width of the sub-waveguide in each of the directional couplers is within ⁇ 10%, and the coupling portion of the sub-waveguide and the main The distance from the waveguide or the length of the coupling portion of the sub-waveguide may be different among all the directional couplers.
  • the optical multiplexer may be an MMI type optical multiplexer.
  • the optical multiplexer may be a Y-type optical multiplexer.
  • the core material may be Si, and the clad material may be SiO 2 .
  • the sub waveguide may separate a higher order mode from the main waveguide.
  • the optical waveguide element may further include a light absorption layer disposed at a tip of the end portion of the sub-waveguide and doped with impurities at a high concentration.
  • the optical waveguide element may further include a light receiving element and an electric wiring for extracting a current of the light receiving element at a tip of an end portion of the sub waveguide.
  • the optical waveguide device includes a main waveguide capable of guiding at least two types of propagation modes having different propagation orders, and a constant waveguide from the main waveguide so as to constitute a directional coupler.
  • n core / n clad which is a refractive index ratio between the core and the clad constituting the main waveguide and the sub waveguide, is within a range of 101 to 250%.
  • the difference between the width of the main waveguide and the width of the sub waveguide in the directional coupler may be within ⁇ 10%.
  • the difference between the thickness of the main waveguide and the thickness of the sub waveguide in the directional coupler may be within ⁇ 10%.
  • the sub-waveguide may further include a start portion that is continuous with the front end portion of the coupling portion, and may gradually approach the main waveguide as the start portion approaches the front end portion.
  • the sub-waveguide may further include an end portion that is continuous with an end portion at the rear stage of the coupling portion, and may gradually move away from the main waveguide as the end portion moves away from the end portion at the rear stage.
  • the optical waveguide element includes a plurality of the mode splitters, and a difference between the width of the main waveguide and the width of the sub waveguide in each directional coupler is within ⁇ 10%, The distance between the coupling portion and the main waveguide and the length of the coupling portion of the sub waveguide may be equal among all the directional couplers.
  • the optical waveguide element includes a plurality of the mode splitters, and the difference between the width of the main waveguide and the width of the sub waveguide in each of the directional couplers is approximately the same as the main waveguide within ⁇ 10%.
  • the core material may be Si, and the clad material may be SiO 2 .
  • the sub waveguide may be configured to separate a higher order mode from the main waveguide.
  • the optical waveguide device may further include a light absorption layer provided at a tip of the end portion of the sub-waveguide and doped with impurities at a high concentration.
  • a light receiving element and an electric wiring for taking out a current of the light receiving element may be further provided at the end of the end portion of the sub waveguide.
  • mode separation is possible by the mode splitter. Further, according to the optical waveguide device according to the aspect of the present invention, in the optical waveguide device in which the waveguide capable of guiding two or more kinds of propagation modes is connected to the rear stage of the optical multiplexer, Mode separation is possible from the optical waveguide by a mode splitter.
  • FIG. 1B is a partially enlarged plan view showing the MMI type optical multiplexer / demultiplexer of FIG. 1A.
  • FIG. 1B is a partially enlarged plan view showing the mode splitter of FIG. 1A. It is sectional drawing which follows the SS line
  • 1A to 1D show an optical waveguide device according to the first embodiment of the present invention.
  • the optical waveguide device 10 includes an optical waveguide having a core 2 and a clad 3 on a substrate 1.
  • 1A to 1C only a portion corresponding to the core 2 is illustrated and described as an optical waveguide.
  • the optical waveguide device 10 includes an optical multiplexer 14 that combines a plurality of input lights into one output light, and a mode splitter 20 that is provided at a subsequent stage on the output side of the optical multiplexer 14.
  • the plurality of input lights are injected into the optical multiplexer 14 through the plurality of incident-side waveguides 11 and 12, respectively.
  • the output light of the optical multiplexer 14 is injected into the mode splitter 20 via the emission side waveguide 13.
  • the optical multiplexer (coupler) is not particularly limited, and examples thereof include an MMI type multiplexer, a Y type multiplexer, and a directional coupler.
  • the waveguides (main waveguides) 11, 12, and 13 connected to the optical multiplexer 14 are multimode waveguides that guide light in multimode.
  • the waveguides 11, 12, and 13 it is preferable to use waveguides having a wide core width, such as multimode waveguides, because the waveguide characteristics are hardly deteriorated due to surface roughness.
  • the mode splitter 20 includes a main waveguide 21 connected to the output-side waveguide 13 of the optical multiplexer 14 and a sub-waveguide 22 provided away from the main waveguide 21.
  • the main waveguide 21 is desirably a waveguide capable of guiding at least two types of propagation modes having different propagation orders.
  • a waveguide having a wide core width such as a multimode waveguide is used as the main waveguide 21
  • the sub waveguide 22 separates at least one propagation mode having different propagation orders from the main waveguide 21 among at least two propagation modes having different propagation orders that can be guided by the main waveguide 21.
  • the main waveguide 21 and the sub-waveguide 22 have coupling portions 21b and 22b that are placed in parallel to each other with a certain distance therebetween, and the directional coupler having a length L 0 by these coupling portions 21b and 22b. Is configured. Further, in the illustrated mode splitter 20, the main waveguide 21 and the sub-waveguide 22 approach each other gently at the start portions 21 a and 22 a that are continuous with the front ends of the coupling portions 21 b and 22 b constituting the directional coupler.
  • the mode splitter 20 has a structure in which the main waveguide 21 and the sub-waveguide 22 are gently separated from each other at the end portions 21c and 22c continuous to the end portions of the subsequent stages of the coupling portions 21b and 22b.
  • the sub waveguide 22 may be a waveguide capable of guiding at least two types of propagation modes having different propagation orders.
  • a directional coupler can be formed by placing the sub-waveguide in parallel at a position close to the main waveguide. Forming a directional coupler generally couples any mode of the main waveguide with the mode of the sub-waveguide.
  • the strength of coupling from the main waveguide mode to the sub-waveguide mode is represented by a coupling coefficient ⁇ 21 shown in the following equation (1).
  • C is a constant including a normalization constant
  • n core is the refractive index of the core
  • n clad is the refractive index of the cladding.
  • Subscripts 1 and 2 represent the eigenmodes (E 1 and E 2 ) of the main waveguide and the sub waveguide, respectively.
  • x and y are the width direction and thickness direction of the waveguide, and the integration range is in the core cross section of the sub-waveguide.
  • the magnitude of the coupling coefficient depends on how much the electromagnetic field distribution of the eigenmode of the main waveguide extends within the core cross section of the sub-waveguide.
  • the fundamental mode propagates in the center of the core, whereas the higher order mode propagates outside the waveguide as compared with the fundamental mode (for example, Example 1 described later).
  • FIG. 10A and FIG. 10B Therefore, it is expected that higher-order modes such as the first-order mode are more easily coupled to the sub-waveguide than the fundamental mode.
  • the distance between two waveguides forming the directional coupler for example, see the distance w 0 in FIG.
  • the coupling coefficient decreases in both the fundamental mode and the higher-order mode.
  • the coupling coefficient of the fundamental mode is drastically reduced as compared with the coupling coefficient of the higher-order mode such as the first-order mode (see, for example, FIG. 11 of Example 1 described later). Therefore, by appropriately selecting the interval between the two waveguides forming the directional coupler, the difference in the coupling coefficient ⁇ 21 is sufficiently increased between two or more types of propagation modes that can be guided by the main waveguide. be able to.
  • the coupling coefficient ⁇ 21 is proportional to n core 2 ⁇ n clad 2 with respect to the refractive index n core of the core and the refractive index n clad of the cladding. For this reason, in order to increase the difference in coupling coefficient between modes, it is preferable to employ a waveguide structure having a large difference in refractive index.
  • n core / n clad is preferably in the range of 101 to 250%.
  • the core material is Si (refractive index of about 3.475) and the clad material is SiO 2 (refractive index of about 1.444)
  • a semiconductor material such as an SOI (Silicon On Insulator) substrate is a waveguide. Since it can be used for a material, it is preferable.
  • the core material include SiO x (refractive index: 1.47), SiON, SiN, or a non-silicon based semiconductor material (compound semiconductor).
  • the maximum power transfer rate is 100% if the two waveguide structures (material, dimensions, shape, etc.) are perfectly symmetrical. Conversely, when the two waveguide structures are different and the mode propagation constants are different, the maximum power transfer rate is less than 100%. Therefore, when efficiently transferring a higher-order mode such as the primary mode from the main waveguide to the sub-waveguide, the waveguide structures (material, dimensions, shape, etc.) of the main waveguide and the sub-waveguide should be the same as much as possible. Is desirable.
  • the main waveguide width and the sub waveguide width is preferably a substantially identical.
  • an Si optical waveguide is manufactured at a low cost
  • an old-generation exposure machine using KrF (248 nm) as a light source is also used.
  • KrF 248 nm
  • a general method for forming a waveguide core there is a possibility that an error caused by alignment accuracy of an exposure mask or etching accuracy may occur. Therefore, when there is no intentional change in the waveguide width (core width) such as a taper shape (see the prior art), for example, the difference between the main waveguide width and the sub-waveguide width is within ⁇ 10%. It is preferable. Similarly, the difference between the thickness of the main waveguide and the thickness of the sub waveguide is preferably within ⁇ 10%, for example.
  • the length of the directional coupler required until the power shift from the main waveguide to the sub waveguide is maximized is called a coupling length.
  • the bond length depends on the strength of the coupling coefficient ⁇ 21 . In general, the smaller the coupling coefficient ⁇ 21 is, the longer the coupling length is (see, for example, FIGS. 11 and 12 of Example 1 described later). For example, under the condition that the coupling length of the fundamental mode is sufficiently longer than the coupling length of the higher-order mode, the length of the directional coupler is shortened (for example, the length of the directional coupler is set as the coupling length of the higher-order mode).
  • the specific higher order mode (for example, the first mode) is sub-guided from the main waveguide.
  • a mode splitter having a structure that can be separated into waveguides can be realized.
  • the length of the directional coupler is longer than the coupling length of the higher-order mode, the higher-order mode shifts alternately between the main waveguide and the sub-waveguide. Therefore, for example, when the length of the directional coupler is set to be approximately the same as the coupling length of the fundamental mode and the ratio of the higher-order mode shifting to the secondary waveguide is reduced, the fundamental mode is changed from the primary waveguide to the secondary waveguide.
  • a mode splitter having a structure that can be separated into a waveguide is considered.
  • a directional coupler is formed by disposing a sub-waveguide having substantially the same width as the main waveguide in parallel with the main waveguide at a position near the main waveguide after the multiplexer. Further, the length of the directional coupler and the distance between the main waveguide and the sub-waveguide are appropriately set by utilizing the fact that the coupling constant is remarkably different between the fundamental mode light and the higher-order mode light. Accordingly, it is possible to separate only the higher-order mode light from the main waveguide to the sub-waveguide while suppressing loss of the fundamental mode light, and it is possible to configure a multiplexer that outputs only the fundamental mode light.
  • the sub-waveguide 22A has a coupling portion 22b that is a portion constituting the directional coupler and an end portion 22c that extracts the light of the mode separated by the coupling portion 22b.
  • the sub-waveguide does not have the start portion (reference numeral 22a in FIG. 1C) of the structure in which the sub-waveguide approaches the main waveguide gently.
  • the main waveguide 31 is entirely linear from the start portion 31a through the coupling portion 31b to the end portion 31c.
  • the sub-waveguide 32 of the mode splitter 30 includes a start portion 32a having a structure in which the sub-waveguide gently approaches the main waveguide, a coupling portion 32b that is a portion constituting the directional coupler, and a mode separated by the coupling portion 32b. And an end portion 32c for extracting the light.
  • the main waveguide 31 is entirely linear from the start portion 31a through the coupling portion 31b to the end portion 31c.
  • the sub-waveguide 32A of the mode splitter 30A has a coupling portion 32b that is a portion constituting a directional coupler and an end portion 32c that extracts light of a mode separated by the coupling portion 32b. It does not have a starting portion (reference numeral 32a in FIG. 2B) of the structure that gently approaches.
  • the same devices as the mode splitters 20A, 30, and 30A shown in FIGS. 2A to 2C may be used for each mode splitter.
  • the main waveguide 21 is a straight line and the sub-waveguide 22 is a curve.
  • the main waveguide 21 may be a curve and the sub-waveguide 22 may be a straight line.
  • the main waveguide and the sub-waveguide have a symmetrical planar shape as shown in FIG. 1C at least at a position close to the directional coupler.
  • the influence of the symmetry between the main waveguide and the sub-waveguide is determined by a finite difference time domain (FDTD) method in Example 2 (particularly, a comparison between FIGS. 18A and 18B). It has been compared by electromagnetic field simulation. 2B is obtained by bending the end portion 31c of the main waveguide of the mode splitter 30A of the optical waveguide element shown in FIG. 2C with the same bending structure as that of the end portion 32c of the sub-waveguide.
  • FDTD finite difference time domain
  • the start portion 31a of the main waveguide of the mode splitter 30 of the optical waveguide device shown in FIG. 2B is bent with the same bending structure as the start portion 32a of the sub-waveguide, and the end portion 31c of the main waveguide is the end portion of the sub-waveguide.
  • the mode splitter 20 having the symmetry shown in FIG. 1C is obtained by bending with a bending structure similar to that of 32c.
  • the intermediate line of the coupling portions 21b and 22b constituting the directional coupler is set as the symmetry center line (symmetric axis), and the main waveguide start portion 21a and the sub-waveguide start portion 22a are led.
  • the coupling portion 21b of the waveguide and the coupling portion 22b of the sub waveguide, and the end portion 21c of the main waveguide and the termination portion 22c of the sub waveguide are provided so as to be symmetrical.
  • the curvature radius of the curved portion (21a, 21c) of the main waveguide is equal to the curvature radius of the curved portion (22a, 22c) of the sub waveguide, or the curvature radius of the curved portion (21a, 21c) of the main waveguide is the sub waveguide.
  • the radius of curvature of the curved portions (22a, 22c) is larger than the radius of curvature of the curved portions (21a, 21c) of the main waveguide or smaller than the radius of curvature of the curved portions (22a, 22c) of the sub waveguide Is possible.
  • the waveguide can be extended or bent so as to have a desired arrangement on the substrate, and the direction and length of the waveguide, etc. Can be set freely.
  • the widths of the main waveguide and the sub-waveguide can be made substantially the same as a whole as well as the position close to the directional coupler.
  • the sub-waveguide has a start portion of a structure that gently approaches the main waveguide because loss can be further reduced.
  • the influence of the sub-waveguide on the fundamental mode of the main waveguide is comparatively examined by electromagnetic field simulation using the FDTD method (described above) in Example 2 (particularly, comparison of FIGS. 18B and 18C). 2B is obtained by bending the start portion of the sub-waveguide of the mode splitter 30A of the optical waveguide element shown in FIG. 2C with the same bending structure as the end portion 32c of the sub-waveguide. It is done. Similarly, a mode splitter having a gentle approach portion shown in FIG.
  • 1A is formed by bending the start portion of the sub-waveguide of the mode splitter 20A of the optical waveguide element shown in FIG. 2A with the same bending structure as the end portion 22c of the sub-waveguide. 20 is obtained. If the sub-waveguide appears discontinuously in the vicinity of the light passing through the main waveguide, light reflection or disturbance is likely to occur, and the loss of light increases. These losses can be further reduced when the sub-waveguide approaches the main waveguide gently. Similarly, when the sub-waveguide has an end portion of a structure that is gently separated from the main waveguide, it is preferable because the loss of light can be further reduced.
  • the structure in which the main waveguide and the sub waveguide are gradually approached or separated is configured along a curve such as an arc, an elliptical arc, a parabola, or a hyperbola.
  • the curvature radius of the curve is preferably 10 ⁇ m or more, for example. Since the curvature radius of the straight line is ⁇ , there is no particular upper limit to the curvature radius for continuously connecting the straight line portion and the curved portion, but the curvature radius of the curved portion adjacent to the straight line portion is, for example, several tens to Several hundred ⁇ m can be mentioned.
  • the bisector perpendicular to the coupling portions 21b and 22b constituting the directional coupler is set as a symmetry center line (symmetric axis), and the main waveguide start portion 21a and the main waveguide end portion 21c.
  • the start portion 22a of the sub-waveguide and the end portion 22c of the sub-waveguide are provided so as to be symmetrical. It is possible to select whether the radius of curvature of the start portion is equal to the radius of curvature of the end portion, whether the radius of curvature of the start portion is larger than the radius of curvature of the end portion, or whether the radius of curvature of the start portion is smaller than the radius of curvature of the end portion It is.
  • FIG. 3 shows a second embodiment of the optical waveguide device.
  • the optical waveguide device 10 configured by combining the optical multiplexer 14 and the mode splitter 20 similar to those in FIG. 1A is formed by providing a cascade type continuously in multiple stages.
  • the optical waveguide device 10 is configured by a 2 ⁇ 1 multiplexer (2 inputs and 1 output), whereas the optical waveguide device of FIG. 3 is configured by a 4 ⁇ 1 (4 inputs and 1 output) multiplexer.
  • an N ⁇ 1 (N input 1 output) multiplexer such as an 8 ⁇ 1 multiplexer, a 16 ⁇ 1 multiplexer, or a 32 ⁇ 1 multiplexer can be configured by overlapping a plurality of stages.
  • each optical waveguide element 10 is shifted to the sub-waveguide 22 at a position sufficiently away from the main waveguide 21, and the separated propagation mode (for example, higher order mode) is absorbed or radiated in a direction away from the main waveguide. . Thereby, recombination to the main waveguide 21 can be suppressed.
  • the separated propagation mode is absorbed in the substrate, for example, a light absorption layer 23 (see FIG. 5) described later is provided at the tip of the end portion 22 c of the sub-waveguide 22.
  • the end portion of the sub waveguide 22 can be extended to the peripheral edge of the substrate and radiated toward the outside of the substrate.
  • FIG. 4 shows a third embodiment of the optical waveguide element.
  • an optical demultiplexer 42 that demultiplexes one input light into two output lights (demultiplexed light) before the light is input to the mode splitter 20, and 2
  • a Mach-Zehnder type optical modulator 40 composed of an optical multiplexer 46 that multiplexes one input light (demultiplexed light) into one output light and an optical modulator 45 is arranged.
  • One output light of the optical demultiplexer 42 is input to the optical multiplexer 46 via the waveguide 43 having the optical modulator 45, and the other output light of the optical demultiplexer 42 does not have the optical modulator 45.
  • the light is input to the optical multiplexer 46 via the waveguide 44.
  • the light injected into the optical demultiplexer 42 from the optical waveguide 41 in the previous stage of the optical demultiplexer 42 is demultiplexed into two and propagates through different waveguides (arms) 43 and 44, respectively.
  • the light modulator 45 is generally a phase modulator.
  • the optical multiplexer 46 combines them.
  • the waved light is modulated according to the phase difference. For example, switching between the on state and the off state of the optical signal is controlled by the phase difference between the two lights injected into the optical multiplexer 46.
  • the Mach-Zehnder type optical modulator 40 When two lights are injected into the optical multiplexer 46 with the same phase, the combined light propagates in the optical waveguide 47 in the subsequent stage in the fundamental mode, and the optical signal is turned on. On the other hand, when two lights are injected into the optical multiplexer 46 with opposite phases, the combined light propagates in the first-order mode to the optical waveguide 47 in the subsequent stage, and the optical signal is turned off.
  • the Mach-Zehnder type optical modulator 40 By connecting the optical waveguide 47 downstream of the optical multiplexer 46 of the Mach-Zehnder type optical modulator 40 to the main waveguide 21 of the mode splitter 20 and separating the primary mode light into the sub-waveguide 22, the Mach-Zehnder type optical modulator 40. It is possible to suppress the deterioration of the extinction ratio.
  • the MMI type multiplexer 14 may be used as the optical multiplexer 46.
  • the relationship between the MMI type multiplexer 14 and the mode splitter 20 can be configured in the same manner as the optical waveguide element 10 in FIG. 1A.
  • the optical demultiplexer 42 and the optical multiplexer 46 of the Mach-Zehnder optical modulator 40 are not particularly limited.
  • the MMI type demultiplexer or multiplexer, the Y type demultiplexer or multiplexer, or the direction Examples include sex couplers.
  • the front stage (waveguide 41) which is the input side of the optical demultiplexer 42, the rear stage (waveguide 47) which is the output side of the optical multiplexer 46, or the optical branch It can be provided at one or more locations selected from the inside (waveguides 43, 44) between the wave multiplier 42 and the optical multiplexer 46. That is, the mode splitter 20 can be provided in at least one of the waveguides 41, 43, 44, and 47 that guide the input light, the demultiplexed light, and the output light in the Mach-Zehnder optical modulator 40.
  • FIG. 5 shows a fourth embodiment of the optical waveguide device.
  • the optical waveguide device according to the present embodiment includes a light absorption layer 23 doped with impurities at a high concentration at the end of the end portion of the sub-waveguide 22 of the mode splitter 20.
  • the light absorption layer 23 may be provided at the end of the end portion of the sub-waveguide 22. Good.
  • FIG. 6 shows a fifth embodiment of the optical waveguide device.
  • a light receiving element (PD: Photo Detector) 24 and an electric wiring 25 for taking out the current of the PD 24 are provided at the tip 22d of the end portion 22c of the sub-waveguide 22 of the mode splitter 20.
  • PD Light receiving element
  • an electric wiring 25 for taking out the current of the PD 24 are provided at the tip 22d of the end portion 22c of the sub-waveguide 22 of the mode splitter 20.
  • the PD 24 By installing the PD 24, it is possible to monitor the light amount of the higher-order mode light branched to the sub waveguide 22. By this monitoring, it is possible to detect a shift in operation due to, for example, aged deterioration or an environmental change such as temperature during driving.
  • the optical multiplexer 14 is incorporated in the Mach-Zehnder optical modulator 40 (see FIG.
  • the PD 24 and the electrical wiring 25 are provided at the end of the end portion 22c of the sub-waveguide 22. May be.
  • the control unit uses the monitoring result using the PD 24 to operate the optical modulator 45 (for example, an applied voltage in the case of electric control). ) Can be fed back.
  • the PD is preferably arranged on the substrate, the PD may be mounted on the substrate.
  • the PD can be integrated as a semiconductor element on the same substrate as the optical waveguide.
  • Examples of PDs that can be integrated on a Si substrate having a Si / SiO 2 waveguide include group IV semiconductor PDs such as germanium (Ge) PD, indium phosphide (InP) -based PDs, or gallium arsenide (GaAs). Examples include III-V compound semiconductor PD.
  • group IV semiconductor PDs such as germanium (Ge) PD, indium phosphide (InP) -based PDs, or gallium arsenide (GaAs).
  • Examples include III-V compound semiconductor PD.
  • two electric wirings 25 can be provided on the substrate (via an insulating layer if necessary), for example, two in parallel for each PD 24.
  • the sub-waveguide 22 and the main waveguide 21 have end portions 21c and 22c having a structure in which they are gently separated from each other. The radius of curvature of the tip 22d of the end portion 22c of the sub-waveguide gradually increases toward the PD 24, and finally the linear waveguide
  • the bending loss of the higher-order mode light at the end portion 22c of the sub waveguide can be reduced by increasing the radius of curvature at the end portion 22c of the sub waveguide. it can.
  • the end portion 22c of the sub waveguide a straight line while leaving the curved portion of the end portion 21c of the main waveguide 21.
  • the directional coupler does not have symmetry, and the removal rate of the higher-order mode of the main waveguide 21 is reduced, but the bending loss of the separated higher-order mode light can be reduced.
  • the end portion 22c may be extended on the extension line of the coupling portion 22b while the start portion 22a of the sub waveguide is bent as shown in FIG.
  • a portion close to the coupling portion 22b is bent to some extent away from the main waveguide 21, and a portion away from the main waveguide 21 to a certain extent is a straight line to the PD 24 (the extension of the coupling portion 22b). It is also possible to incline against).
  • the end portion of the sub-waveguide 22 is substantially the same until reaching the light absorption layer 23 or the PD 24. It is preferable that the width is formed. As a result, the light absorption layer 23 or the PD 24 can be disposed at a desired position on the substrate, and higher-order mode light branched to the sub waveguide 22 can be prevented from leaking from the sub waveguide 22 into the substrate. As shown in FIG. 3, FIG. 7A, FIG. 7B, and FIG. 8, when the optical waveguide device has two or more sub-waveguides 22, at least one of the end portions of the sub-waveguides 22 has light at the end thereof.
  • An absorption layer 23 or a PD 24 can be provided. It is possible to arbitrarily design, for example, by providing the light absorption layer 23 at the end of the end portion of any sub-waveguide 22 and providing the PD 24 at the end of the end portion of another sub-waveguide 22.
  • FIG. 7A shows a sixth embodiment of the optical waveguide device.
  • the optical waveguide device according to the present embodiment there are two or more sub-waveguides 22 at different positions in the longitudinal direction of the main waveguide 21 in the subsequent stage of the optical multiplexer 14, and the width of each sub-waveguide 22 is the main waveguide.
  • the difference with the width of 21 is within ⁇ 10%, which is substantially the same as the width of the main waveguide 21.
  • the distance between the sub waveguide 22 and the main waveguide 21 (interval w 0 in FIG. 1D) and the length of the portion where the sub waveguide 22 is placed in parallel with the main waveguide 21 (the length of the coupling portions 21b and 22b in FIG. 1C).
  • L 0 L 0
  • the removal rate of light (for example, primary mode light) to be separated into the sub-waveguide 22 can be increased.
  • FIG. 7B shows a seventh embodiment of the optical waveguide device.
  • two or more sub-waveguides 22 are provided at different positions in the longitudinal direction of the main waveguide 21 in the subsequent stage of the optical multiplexer 14, and the width of each sub-waveguide 22 is the main The difference from the width of the waveguide 21 is within ⁇ 10%, which is substantially the same as the width of the main waveguide 21.
  • the distance between the sub-waveguide 22 and the main waveguide 21 or the length of the portion where the sub-waveguide 22 is placed in parallel with the main waveguide 21 is different, and each sub-waveguide 22 is in a portion along the main waveguide 21.
  • Mode splitters 20 and 200 having different wavelength characteristics are formed.
  • the wavelength band from which light (for example, primary mode light) to be separated into the sub-waveguide 22 is removed can be expanded.
  • the mode splitter 200 has a larger distance between the sub waveguide 22 and the main waveguide 21 than the mode splitter 20, but the present invention is not particularly limited to this.
  • FIGS. 7A and 7B a configuration in which two or more sub waveguides 22 are provided at different positions in the longitudinal direction of the main waveguide 21 in the subsequent stage of the 2 ⁇ 1 (two inputs and one output) optical multiplexer 14. It is. However, when the mode splitter 20 is provided after the N ⁇ 1 (N input 1 output) optical multiplexer (see FIG. 3 and FIGS. 9A and 9B described later), and the optical multiplexer of the Mach-Zehnder optical modulator 40 Similarly, in other embodiments, such as when the mode splitter 20 is provided at the subsequent stage of 46 (see FIG. 4), two or more sub-waveguides 22 can be provided at different positions in the longitudinal direction of the main waveguide 21.
  • the width of each sub-waveguide 22 is preferably within ⁇ 10% of the width of the main waveguide 21.
  • the removal rate of light for example, primary mode light
  • the wavelength band removed by the sub-waveguide 22 can be widened.
  • FIG. 8 shows an eighth embodiment of the optical waveguide device.
  • the optical waveguide device according to the present embodiment is configured in the same manner as the optical waveguide device 10 of FIG. 1A except that the optical waveguides 11 and 12 provided in the previous stage of the optical multiplexer 14 also have a mode splitter 20. ing.
  • the optical waveguides 11, 12, 13 at the front stage and the rear stage of the optical multiplexer 14 constitute the main waveguide 21, and the mode splitter 20 is provided at each of the optical waveguides 11, 12, 13.
  • the mode splitter 20 according to each of the embodiments of the present invention is not limited to the case where the mode splitter 20 is provided in the optical waveguide 13 at the rear stage of the optical multiplexer 14 as shown in FIG. It can also be provided only.
  • the present invention is not limited to the case where it is provided in both of the optical waveguides 11 and 12 in the previous stage of the optical multiplexer 14, and can be provided in only one of the optical waveguides 11 and 12 in the previous stage of the optical multiplexer 14.
  • FIG. 9A shows a ninth embodiment of the optical waveguide device.
  • the optical waveguide device according to the present embodiment has the same configuration as that of the optical waveguide device 10 of FIG. 1A except that the optical multiplexer includes a Y-type multiplexer 15 as an optical multiplexer.
  • the Y-type multiplexer 15 can be used instead of the MMI-type multiplexer 14.
  • a Y-type demultiplexer and multiplexer can be used as the optical demultiplexer 42 and optical multiplexer 46 of the Mach-Zehnder optical modulator 40 shown in FIG. 4 a Y-type demultiplexer and multiplexer can be used.
  • FIG. 9B shows a tenth embodiment of the optical waveguide device.
  • the optical waveguide device according to the present embodiment has the same configuration as that of the optical waveguide device 10 in FIG. 1A except that the optical multiplexer includes a 3 ⁇ 1 (3-input, 1-output) MMI multiplexer 16 as an optical multiplexer.
  • the optical multiplexer includes a 3 ⁇ 1 (3-input, 1-output) MMI multiplexer 16 as an optical multiplexer.
  • a 3 ⁇ 1 MMI multiplexer 16 is used instead of the 2 ⁇ 1 MMI multiplexer 14. Can be used.
  • FIG. 9C shows an eleventh embodiment of the optical waveguide device.
  • the optical waveguide device according to the present embodiment has an N ⁇ 1 (N input 1 output) MMI multiplexer 17 (where N ⁇ 4) as an optical multiplexer, and the optical waveguide of FIG.
  • the configuration is the same as that of the waveguide element 10.
  • an N ⁇ 1 MMI multiplexer 17 is used instead of the 2 ⁇ 1 MMI multiplexer 14. Can be used.
  • the cladding region was formed of SiO 2 and the core region was formed of Si.
  • the thickness of the waveguide core region (see t 0 in FIG. 1D) was 220 nm, and the width of the waveguide core region (see w 1 and w 2 in FIG. 1D) was 500 nm. Clads were provided above and below the core to prevent light from touching the substrate and air, respectively.
  • the thickness of the clad (see t 1 and t 2 in FIG. 1D) was 2 ⁇ m above and below the core, respectively.
  • the clad was also formed on the side of the core and between the waveguides.
  • the electromagnetic field distribution in the fundamental mode and the primary mode when the above optical waveguide is arranged alone was analyzed by simulation.
  • the analysis results of the electromagnetic field distribution are shown in FIGS. 10A and 10B. It was found that the fundamental mode shown in FIG. 10A propagates in the center of the core, whereas the higher-order mode shown in FIG. 10B propagates outside the waveguide compared to the fundamental mode.
  • An MMI multiplexer was used as the optical multiplexer.
  • the width of the MMI duplexer (see WMMI in FIG. 1B) was 1.5 ⁇ m, and the length (see LMMI in FIG. 1B) was 1.7 to 1.9 ⁇ m.
  • two waveguides were coupled to the incident side of the MMI multiplexer, and one waveguide was coupled to the exit side opposite to the incident side.
  • a waveguide on the rear stage (outgoing side) of the optical multiplexer was used as a main waveguide, and a sub-waveguide was placed in parallel with and spaced from the main waveguide.
  • the waveguide width of the sub-waveguide was made the same as that of the main waveguide. If the interval between the main waveguide and the sub-waveguide (waveguide interval) is too close, the coupling of the fundamental mode from the main waveguide to the sub-waveguide becomes strong, and the loss of the fundamental mode light increases. Conversely, if the sub-waveguide is too far away from the main waveguide, the coupling of the primary mode from the main waveguide to the sub-waveguide becomes weak, and a very long sub-waveguide length is required.
  • the coupling coefficient was calculated from the result of mode analysis by the finite element method for the directional coupler in which the two optical waveguides are arranged, and the coupling length was calculated from the coupling coefficient.
  • the waveguide interval was set every 0.05 ⁇ m within the range of 0.15 to 0.85 ⁇ m. This setting was applied to all the mode analyzes shown in FIGS.
  • FIG. 11 shows the result of determining the relationship between the coupling coefficient and the waveguide interval. As the waveguide spacing increases, the fundamental mode and primary mode coupling coefficients ⁇ both decrease, but the fundamental mode coupling coefficient ⁇ decreases more rapidly than the primary mode coupling coefficient ⁇ . It turns out that. Further, FIG.
  • the waveguide 12 shows the result of obtaining the relationship between the coupling length and the waveguide interval.
  • the coupling length of the fundamental mode is 504 ⁇ m, but the coupling length of the primary mode is 16 ⁇ m. Since the coupling efficiency and the coupling length of the fundamental mode and the primary mode are determined by the waveguide interval, the length of the portion where the sub waveguide is parallel along the main waveguide (sub waveguide length) is the coupling length of the primary mode. It was equal to. Assuming that the main waveguide and the sub-waveguide are symmetrical, the primary mode light can be transferred to the sub-waveguide 100% if the sub-waveguide length is equal to the coupling length of the primary mode.
  • the primary mode at a plurality of waveguide intervals The relationship between the light intensity and the sub-waveguide length was obtained. The result is shown in FIG. From this result, it is understood that when the waveguide interval is narrow, the coupling coefficient is large, the light reaches the maximum transition point with a short sub-waveguide length, and then the light returns from the sub-waveguide to the main waveguide.
  • the coupling length of the first-order mode confirmed from FIG. 14 substantially matches the coupling length shown in FIG. 12 calculated by the finite element method.
  • the reason why the maximum power transfer efficiency is small when the sub-waveguide length is short is considered to be due to the influence of asymmetry at the start and end points of the sub-waveguide.
  • the coupling becomes small, and the transition to the sub-waveguide is not seen unless the sub-waveguide length is increased.
  • the relationship between the extinction ratio and the sub-waveguide length at multiple waveguide intervals was obtained It was.
  • the result is shown in FIG. It can be seen that the general tendency of the extinction ratio of the main waveguide is determined by the amount of decrease in the residual light at the time of OFF, and it is advantageous to increase the sub-waveguide length after widening the waveguide interval.
  • the fundamental mode light loss is large when the waveguide interval is 0.4 ⁇ m or less, it is considered that the waveguide interval is preferably larger than 0.4 ⁇ m.
  • Example 1 the waveguide interval (see w 0 in FIG. 1D) was set to 0.5 ⁇ m (500 nm), and the sub-waveguide length was set to 16 ⁇ m. At this time, the extinction ratio is 21.93 dB, and an improvement of about 12.5 dB is expected as compared with the extinction ratio of 9.37 dB when the sub-waveguide is not provided.
  • the directional coupler was used as the subsequent mode splitter, the change in characteristics due to the change in wavelength was verified. Furthermore, the wavelength dependence of the extinction ratio (ER) was calculated by changing the incident wavelength under the above-mentioned conditions (waveguide interval 0.5 ⁇ m, sub-waveguide length 16 ⁇ m). The results (wavelength 1.53 to 1.61 ⁇ m) are shown in FIG. Although the extinction ratio is reduced on the long wavelength side, the extinction ratio is improved by 4 dB or more compared with the case where the sub-waveguide is not formed (“woBP” in FIG. 16), and the entire region of C-band and L-band It was found that there is an effect of improving the extinction ratio.
  • the loss (loss) of the fundamental mode light due to the provision of the sub waveguide in Example 1 was calculated.
  • the results (wavelength 1.53 to 1.61 ⁇ m) are shown in FIG.
  • the loss of fundamental mode light is 0.016 dB or less over the entire range of C-band and L-band, which is considered not to cause a problem in practice.
  • a bent portion that is gently separated from the main waveguide is provided at the end of the sub-waveguide so that the primary mode light transferred to the sub-waveguide does not return to the main waveguide again. If the curvature radius of the bent portion is small, the first-order mode light leaks from the sub-waveguide and may recombine with the main waveguide via the cladding. Therefore, the radius of curvature of the bent portion is set to 30 ⁇ m so that the leakage of the first mode light is reduced.
  • Example 2 Also in Example 2, the same optical waveguide structure as in Example 1 was adopted. Specifically, the cladding material is SiO 2 , the core material is Si, the core thickness is 220 nm, the core width (waveguide width) is 500 nm, and the cladding thickness is 2 ⁇ m above and below the core.
  • the cladding material is SiO 2
  • the core material is Si
  • the core thickness is 220 nm
  • the core width (waveguide width) is 500 nm
  • the cladding thickness is 2 ⁇ m above and below the core.
  • FIG. 18 shows how light propagates when primary mode light is injected into the mode splitter.
  • FIG. 18A shows a mode splitter having a structure in which the main waveguide (left side in the figure) is linear, the sub-waveguide (right side in the figure) is the end point side, and the sub-waveguide is gently separated from the main waveguide. Indicates.
  • FIG. 18B shows a mode splitter having a structure in which the main waveguide and the sub-waveguide are gently separated from the other side at the end points.
  • FIG. 18C shows a mode splitter in which the main waveguide and the sub-waveguide have a structure that gently approaches the other side on each start side and a structure that gently leaves the other side on each end side. .
  • the first-order mode light is transferred to the sub-waveguide.
  • the first-order mode light remaining in the main waveguide is slightly recognized in FIG. In FIG. 18B, the primary mode light remaining in the main waveguide is very small, and in FIG. 18C, the primary mode light remaining in the main waveguide cannot be confirmed at all.
  • FIG. 19 shows the result of studying how the branching ratio changes with respect to the length of the straight portion along which the main waveguide and the sub waveguide are parallel to each other in the structure shown in FIG. .
  • the branching ratio here is a value obtained by decibel (dB) display of the ratio between the power of the primary mode light that shifts to the sub-waveguide and the power of the primary mode light that remains in the main waveguide.
  • FIG. 20 shows the results of examining the relationship between the optimized branching ratio and the radius of curvature of the curved portion for the three types of structures shown in FIGS. 18 (a), (b), and (c).
  • the curvature radius of the curved portion 3 to 4 types were selected from 20 ⁇ m, 40 ⁇ m, 60 ⁇ m, and 100 ⁇ m.
  • the results show that the branching ratio is improved by setting (b) as compared to (a) and further by setting (c).
  • the “optimized branching ratio” refers to the branching ratio when the length of the straight line portion is optimized for each structure. Therefore, the branching ratio shown in (c) of FIG. 20 is the same value as the “optimized branching ratio” shown in FIG.
  • the propagation state of the fundamental mode light in the mode splitter in FIG. 18C in which the length of the straight line portion is 2 ⁇ m and the curvature radius of the bent portion is 100 ⁇ m is shown. investigated. The result is shown in FIG. In this result, the fundamental mode light that shifts to the sub-waveguide is completely invisible, and all the fundamental mode light propagates through the main waveguide. Specifically, the branching ratio (loss) was ⁇ 30.5 dB, which was very low loss.
  • a waveguide and an optical multiplexer were configured with the cladding region made of SiO 2 and the core region made of Si.
  • the core thickness was 220 nm, and the core width (waveguide width) was 500 nm. Clads were provided above and below the core to prevent light from touching the substrate and air, respectively. The thickness of the clad was 2 ⁇ m above and below the core. The clad was also formed on the side of the core and between the waveguides.
  • An MMI type multiplexer was used as the optical multiplexer.
  • the width W MMI of the multiplexer / demultiplexer was 1.5 ⁇ m and the length L MMI was 1.8 ⁇ m.
  • the interval between the parallel waveguides was set to 0.3 ⁇ m.
  • a waveguide on the rear stage (outgoing side) of the optical multiplexer was used as a main waveguide, and a sub-waveguide was placed in parallel with and spaced from the waveguide (see FIG. 1A).
  • the waveguide width of the sub-waveguide is set to the same width as that of the main waveguide. Based on the examination of Examples 1 and 2, the distance between the sub waveguide and the main waveguide was set to 0.5 ⁇ m (500 nm).
  • the radius of curvature of the approaching portion and the separating portion is set to 100 ⁇ m in each of the main waveguide and the sub-waveguide, The length was 2 ⁇ m.
  • a waveguide and an optical multiplexer were configured with the cladding region made of SiO 2 and the core region made of Si.
  • the core thickness was 220 nm, and the core width (waveguide width) was 600 nm. Clads were provided above and below the core to prevent light from touching the substrate and air, respectively.
  • the thickness of the clad was 2 ⁇ m above and below the core.
  • the clad was also formed on the side of the core and between the waveguides.
  • An MMI type multiplexer was used as the optical multiplexer.
  • the width W MMI was 1.7 ⁇ m
  • the length L MMI was 2.4 ⁇ m.
  • the interval between the parallel waveguides was set to 0.3 ⁇ m.
  • a waveguide on the rear stage (outgoing side) of the optical multiplexer was used as a main waveguide, and a sub-waveguide was placed in parallel with and spaced from the waveguide (see FIG. 1A).
  • the optimum waveguide interval was examined even with a waveguide width of 600 nm.
  • the interval between the sub-waveguide and the main waveguide was set to 0.5 ⁇ m (500 nm). Further, as shown in FIG. 18C and FIG.
  • the optimum length of the straight portion is obtained by simulation. It was determined to be 9 ⁇ m.
  • the higher-order mode can be efficiently transferred from the main waveguide to the sub-waveguide, and the transition from the fundamental mode to the sub-waveguide can be almost eliminated.

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Abstract

La présente invention se rapporte à un élément à guides d'ondes optiques qui comprend : un multiplexeur optique multiplexant une pluralité de lumières d'entrée pour obtenir une lumière de sortie ; un guide d'ondes principal guidant la lumière d'entrée ainsi que la lumière de sortie, et permettant le guidage d'au moins deux types de mode de propagation qui ont un ordre de propagation différent ; et au minimum un séparateur de mode possédant une section de couplage située parallèlement au guide d'ondes principal à une distance prédéfinie dudit guide d'ondes principal afin de concevoir un coupleur directif, et comportant un guide d'ondes auxiliaire qui peut séparer au moins un type de mode de propagation parmi les deux types de mode de propagation ou plus du guide d'ondes principal. Le rapport d'indice de réfraction (ncore/nclad) entre le cœur et la gaine constituant le guide d'ondes principal et le guide d'ondes auxiliaire est de 101 à 250 %.
PCT/JP2013/071868 2012-08-22 2013-08-13 Élément à guides d'ondes optiques WO2014030578A1 (fr)

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FI124843B (fi) 2012-10-18 2015-02-13 Teknologian Tutkimuskeskus Vtt Taivutettu optinen aaltojohde
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CN114839718B (zh) * 2022-03-03 2023-03-31 上海大学 一种光波导多级耦合模分复用器

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