CN106468810B - Light spot converter and optical device - Google Patents
Light spot converter and optical device Download PDFInfo
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- CN106468810B CN106468810B CN201510516253.9A CN201510516253A CN106468810B CN 106468810 B CN106468810 B CN 106468810B CN 201510516253 A CN201510516253 A CN 201510516253A CN 106468810 B CN106468810 B CN 106468810B
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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
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
- G02B6/421—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms the intermediate optical component consisting of a short length of fibre, e.g. fibre stub
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
- G02B27/0938—Using specific optical elements
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
- G02B27/0938—Using specific optical elements
- G02B27/0944—Diffractive optical elements, e.g. gratings, holograms
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- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Integrated Circuits (AREA)
- Optical Couplings Of Light Guides (AREA)
Abstract
The invention discloses a light spot converter and an optical device, comprising: the optical fiber comprises a first core and a second core covering the first core, wherein the first core is a sub-wavelength grating, and the second core is made of a material with a refractive index larger than that of silicon dioxide by a first proportion, and the first proportion is larger than or equal to 2% and smaller than or equal to 10%. The invention discloses a light spot converter and an optical device, which are used for solving the problem of high processing difficulty of the light spot converter in the prior art.
Description
Technical Field
The present invention relates to the field of optical communications, and in particular, to a light spot converter and an optical device.
Background
Coupling of a silicon optical chip to an optical fiber is very important, and common coupling modes include vertical coupling and edge coupling. The vertical coupling, namely grating coupling, has the characteristics of easy processing, large loss, limited bandwidth and the like; the edge coupling adopts a Spot Converter (SSC) to realize the direct coupling between a small-Size silicon waveguide (such as 400nm multiplied by 200nm) and a large-Size optical fiber (such as the diameter of about 10 mu m), and has the characteristics of small loss, irrelevant polarization, large working bandwidth, large processing difficulty and the like.
Currently, the optical spot converter is generally implemented on the basis of a wedge-shaped waveguide, and then a layer of material with a larger refractive index than silicon dioxide (SiO2) is added on the wedge-shaped waveguide to realize transition, the cross section size is about 3 μm multiplied by 3 μm, and then a lens optical fiber with a mode field diameter of about 3 μm is matched to realize the coupling of the silicon optical chip and the single-mode optical fiber. Fig. 1 is a prior art spot converter. In the dual core (or overlay) spot converter shown in fig. 1, the first core is a tapered waveguide (taper) and the second core is a polymer core. The light spot converter adopting the dual-core structure reduces the alignment difficulty with an external optical fiber, but in order to realize low-loss coupling, the tip (tip) of a wedge waveguide (taper) is often required to be less than 100nm, so that the processing difficulty is very high.
Disclosure of Invention
In order to solve the above technical problems, the present invention provides a light spot converter and an optical apparatus, which are used to solve the problem of the prior art that the light spot converter is difficult to process.
In order to achieve the above technical object, the present invention provides a light spot converter, including: a first core and a second core overlying the first core; the first core is a sub-wavelength grating; the second core is a material having a refractive index greater than that of silica by a first proportion that is greater than or equal to 2% and less than or equal to 10%.
Furthermore, the initial end of the sub-wavelength grating is connected with the conventional waveguide in a bridging waveguide mode, and the tail end of the sub-wavelength grating is close to the coupling optical fiber.
Further, the effective refractive index of the sub-wavelength grating gradually decreases from a start end having the same effective refractive index as that of the conventional waveguide to an end having an effective refractive index greater than that of silica by a second ratio that is 20% or less.
Further, the length of the second core is greater than the length of the first core.
Further, the size of the second core is matched with the size of the circumscribed coupling optical fiber.
further, the sub-wavelength grating amplifies the light spot to the size of the second core, and the external coupling optical fiber focuses light to the size of the second core.
Further, the period of the sub-wavelength grating is 300nm, the duty ratio is 50%, the minimum width is 300nm, and the maximum width is 500 nm.
Further, the light spot converter further includes: a silica coating overlying the second core.
Further, the light spot converter further includes: the first core and the second core are positioned on the silicon dioxide buried layer, and the second core covers all surfaces of the first core, which are not in contact with the silicon dioxide buried layer.
The present invention also provides an optical device comprising: the light spot converter and the coupling optical fiber are coupled to the side end face of the second core of the light spot converter.
Further, the coupling fiber is a lensed fiber.
the light spot converter provided by the invention comprises a first core and a second core covered on the first core, wherein the first core is a sub-wavelength grating, the second core is made of a material with a refractive index larger than that of silicon dioxide by a first proportion, and the first proportion is more than or equal to 2% and less than or equal to 10%. Compared with the prior art, the light spot converter provided by the invention has the advantages of independence on polarization, small loss, small crosstalk and simpler production process. In addition, in the embodiment of the invention, the minimum size of the device can be smaller than the characteristic size of the existing processing technology, and the processing difficulty is small.
Drawings
FIG. 1 is a prior art spot converter;
fig. 2 is a top view of a spot converter according to an embodiment of the invention;
Fig. 3 is a cross-sectional view of a spot converter according to an embodiment of the invention;
FIG. 4 is a schematic structural diagram of a sub-wavelength grating of a spot converter according to an embodiment of the present invention;
FIG. 5 is a top view of Poynting vector when the optical fiber Gaussian source is used in the embodiment of the present invention;
FIG. 6 is a schematic top view of a poynet pavilion in a chip-mode light source according to an embodiment of the present invention;
FIG. 7 is a diagram illustrating the relationship between loss and fiber alignment error of a spot converter according to an embodiment of the present invention.
Detailed Description
the embodiments of the present invention will be described in detail below with reference to the accompanying drawings, and it should be understood that the embodiments described below are only for illustrating and explaining the present invention and are not intended to limit the present invention.
the embodiment of the invention provides a light spot converter, which comprises: a first core and a second core overlying the first core. The first core is a sub-wavelength grating, and the second core is a material with a refractive index greater than that of silicon dioxide by a first proportion, wherein the first proportion is greater than or equal to 2% and less than or equal to 10%.
Specifically, the initial end of the sub-wavelength grating is connected with the conventional waveguide in a bridging waveguide manner, and the tail end of the sub-wavelength grating is close to the coupling optical fiber, specifically, the tail end of the sub-wavelength grating is close to the coupling optical fiber and does not contact the coupling optical fiber. The effective refractive index of the sub-wavelength grating gradually decreases from the beginning to the end, the effective refractive index of the beginning is the same as that of the conventional waveguide, and the effective refractive index of the end is greater than that of the silica by a second proportion, wherein the second proportion is less than or equal to 20%.
the second core has a length greater than the length of the first core. The size of the second core matches the size of the circumscribed coupling fiber. The sub-wavelength grating amplifies the light spot to the size of the second core, and the external coupling optical fiber focuses light to the size of the second core. Therefore, the silicon optical chip and the optical fiber have better mode overlapping, and low-loss optical coupling is realized.
Fig. 2 is a top view of a spot converter according to an embodiment of the invention; fig. 3 is a cross-sectional view of a spot converter according to an embodiment of the invention. Fig. 3 is a cross-sectional view taken along the direction a in fig. 2.
As shown in fig. 2 and 3, the optical spot converter provided in this embodiment includes a sub-wavelength grating (SWG) (i.e., a first core), a second core covering the SWG, a silicon dioxide (SiO2) covering the second core, a buried silicon dioxide layer, and a silicon (Si) substrate disposed under the buried silicon dioxide layer. The first core and the second core are positioned on the silicon dioxide buried layer, and the second core also covers all the surfaces of the first core, which are not contacted with the silicon dioxide buried layer. The buried silicon dioxide layer and the silicon substrate are typically 2 μm in height, and the refractive index of silicon dioxide is about 1.44.
in this embodiment, the first core is a small-sized sub-wavelength grating, and the structure of the SWG is shown in fig. 4. In fig. 4, the black frame is a silicon material, and the others are materials of the second core. Wherein the desired refractive index can be designed by adjusting the period, width or duty cycle of the SWG. For example, in the 1550nm window, the period of the SWG is typically around 300nm or less, and if too large, the index tunable features of the sub-wavelength grating are lost, and if too small, processing difficulties can result. Here, the cycle of the SWG is 300nm, and the duty ratio (a/Ω: 150/300) is 50%. The minimum width Wa of the SWG is 300nm and the maximum width Wb is 500nm, where 500nm is the width of a conventional waveguide. The beginning of the SWG is connected with the conventional waveguide with low loss by using a bridge waveguide, wherein the minimum width of the bridge waveguide is 130nm, and here, 130nm is the minimum feature length allowed by the existing processing technology, however, the present invention is not limited to this, and as the processing technology develops, a smaller width can be adopted, and the maximum width of the bridge waveguide is 500 nm. Here, the length of the bridging waveguide was 10 μm, the length of the SWG was 100 μm, and the height of the SWG was 220 nm.
In this embodiment, the second core is made of a material having a refractive index slightly larger than that of silica, and the size of the second core is larger so as to match the size of the external optical fiber. The second core may be a silicon compound (SiOX, SiON) or various polymers (polymers), also called high molecular compounds, whose refractive index is slightly larger than that of silicon dioxide (1.44) in order to perform guided wave confinement of light, where the refractive index of the second core is between 2% and 10% larger than that of silicon dioxide, and where the refractive index of the second core is, for example, about 1.5. In this embodiment, the size of the second core is 3 μm by 3 μm, where 3 μm matches the size of the corresponding lensed fiber. The length of the second core is greater than the length of the sub-wavelength grating, for example, 105 μm.
Fig. 5 is a top view of a Poynting vector in the case of the fiber gaussian light source according to the embodiment of the present invention. As shown in FIG. 5, when a fiber Gaussian beam (light from fiber) is incident, the waist radius of the Gaussian beam is set to 1.5 μm, the calculated loss is 0.478dB, and the reflection is 37.3 dB.
Fig. 6 is a schematic top view of the poynet pavilion in the chip mode light source according to the embodiment of the invention. As shown in fig. 6, when light is incident from the chip waveguide (light from chip), the calculated loss is 0.132dB and the reflection is 36.7 dB.
Fig. 7 is a diagram illustrating the relationship between Loss (Loss) and fiber alignment error (Offset) of the spot converter according to the embodiment of the invention. In the simulation, the light source is an ideal gaussian beam output by the optical fiber, and as can be seen from fig. 7, the optical fiber alignment error allowed by the light spot converter of the present embodiment is large.
It should be noted that the parameters given in this embodiment are only typical values under specific conditions, and other optimized values can be selected according to the actual technical level of the process and the material of the second core.
In addition, an embodiment of the present invention further provides an optical apparatus, including: the light spot converter is the same as the above embodiments, and therefore, the details are not repeated herein, and the coupling optical fiber is coupled to the side end face of the second core of the light spot converter. Wherein, the coupling fiber is a lens fiber.
In summary, compared with the prior art, the light spot converter provided by the embodiment of the invention has the advantages of independence on polarization, low loss, low crosstalk, smaller minimum size of a device than the characteristic size of the existing processing technology, low processing difficulty and simpler production technology. Furthermore, the invention is also applicable to other integrated optical devices, such as laser out-coupling.
The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. The present invention is not limited to the above-described embodiments, which are described in the specification and illustrated only for illustrating the principle of the present invention, but various changes and modifications may be made within the scope of the present invention as claimed without departing from the spirit and scope of the present invention.
Claims (11)
1. A spot converter, comprising:
The first core is a sub-wavelength grating; the starting end of the sub-wavelength grating is connected with a conventional waveguide in a bridging waveguide mode, and the tail end of the sub-wavelength grating is close to the coupling optical fiber; the effective refractive index of the sub-wavelength grating is gradually reduced from a starting end to a tail end, the effective refractive index of the starting end is the same as that of the conventional waveguide, the effective refractive index of the tail end is larger than that of silicon dioxide by a second proportion, and the second proportion is less than or equal to 20%;
A second core covering the first core, the second core being a material having a refractive index greater than that of silicon dioxide by a first proportion, the first proportion being greater than or equal to 2% and less than or equal to 10%.
2. The spot converter according to claim 1, wherein the sub-wavelength grating terminates adjacent to the coupling fiber and comprises:
The tail end of the sub-wavelength grating is close to the coupling optical fiber and does not contact the coupling optical fiber.
3. The spot converter according to claim 2,
The first core is a small-sized sub-wavelength grating.
4. the spot converter according to claim 1, wherein the second core has a length greater than a length of the first core.
5. the spot converter according to claim 1, wherein the second core has a size that matches a size of the circumscribed coupling fiber.
6. The spot converter according to claim 1, wherein the sub-wavelength grating amplifies the spot to the size of the second core and an external coupling fiber focuses the light to the size of the second core.
7. The spot converter according to claim 1, wherein the sub-wavelength grating has a period of 300nm, a duty cycle of 50%, a minimum width of 300nm, and a maximum width of 500 nm.
8. the spot converter according to claim 1, further comprising: a silica coating overlying the second core.
9. The spot converter according to claim 1, further comprising: the first core and the second core are positioned on the silicon dioxide buried layer, and the second core covers all surfaces of the first core, which are not in contact with the silicon dioxide buried layer.
10. An optical device, comprising:
A spot converter according to any one of claims 1 to 9;
And the coupling optical fiber is coupled to the side end face of the second core of the light spot converter.
11. The optical device of claim 10, wherein the coupling fiber is a lensed fiber.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510516253.9A CN106468810B (en) | 2015-08-20 | 2015-08-20 | Light spot converter and optical device |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510516253.9A CN106468810B (en) | 2015-08-20 | 2015-08-20 | Light spot converter and optical device |
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| CN106468810A CN106468810A (en) | 2017-03-01 |
| CN106468810B true CN106468810B (en) | 2019-12-06 |
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Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110243572B (en) * | 2019-06-28 | 2021-07-27 | 中兴光电子技术有限公司 | Device and method for testing refractive index of optical waveguide group |
| CN113075765A (en) * | 2020-01-06 | 2021-07-06 | 山东大学 | Heterogeneous integrated vertical coupler based on sub-wavelength grating and application thereof |
| CN114153024A (en) * | 2020-09-07 | 2022-03-08 | 苏州旭创科技有限公司 | Optical assembly, photonic integrated chip and coupling structure thereof |
| CN115113329B (en) * | 2022-08-29 | 2022-11-08 | 上海羲禾科技有限公司 | Optical waveguide mode spot conversion device and manufacturing method thereof |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013064940A (en) * | 2011-09-20 | 2013-04-11 | Oki Electric Ind Co Ltd | Diffraction grating type optical coupler |
| CN104570235A (en) * | 2013-10-25 | 2015-04-29 | 富士通株式会社 | Spot size converter and optical apparatus |
| CN104813204A (en) * | 2013-11-13 | 2015-07-29 | 华为技术有限公司 | Waveguide structures, waveguide coupling structures, and manufacturing methods |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JP4003658B2 (en) * | 2003-02-17 | 2007-11-07 | 日立電線株式会社 | Lens array spot size conversion optical circuit |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013064940A (en) * | 2011-09-20 | 2013-04-11 | Oki Electric Ind Co Ltd | Diffraction grating type optical coupler |
| CN104570235A (en) * | 2013-10-25 | 2015-04-29 | 富士通株式会社 | Spot size converter and optical apparatus |
| CN104813204A (en) * | 2013-11-13 | 2015-07-29 | 华为技术有限公司 | Waveguide structures, waveguide coupling structures, and manufacturing methods |
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