CN118244420A - Polarization independent interlayer optical coupler - Google Patents
Polarization independent interlayer optical coupler Download PDFInfo
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- 239000011229 interlayer Substances 0.000 title claims abstract description 42
- 230000010287 polarization Effects 0.000 title claims abstract description 37
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- 230000008878 coupling Effects 0.000 claims abstract description 81
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- 238000009812 interlayer coupling reaction Methods 0.000 claims abstract description 50
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 10
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- 229910052581 Si3N4 Inorganic materials 0.000 claims description 8
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 8
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- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 claims description 4
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims description 4
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- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 4
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Abstract
The invention belongs to the technical field of optical chips, and provides a polarization-independent interlayer optical coupler, wherein the width of a first waveguide layer in a coupling area is in a trend of decreasing in the horizontal direction and in the direction of pointing to a second waveguide layer by the first waveguide layer, the width of a second waveguide layer in the coupling area is in a trend of increasing, a buffer waveguide layer is introduced into the first waveguide layer and the second waveguide layer, or the thickness of at least one waveguide layer in the first waveguide layer and the second waveguide layer is introduced into the thickness of the buffer waveguide layer, so that the transmission of a transverse electric mode and a transverse magnetic mode can be simultaneously supported, and the buffer waveguide layer has extremely low interlayer coupling loss on the transverse electric mode and the transverse magnetic mode.
Description
Technical Field
The invention belongs to the technical field of optical chips, and relates to a polarization-independent interlayer optical coupler.
Background
In recent years, technologies such as artificial intelligence, cloud computing, automatic driving and the like are rapidly developed, and the performance requirements of microelectronic chips are increasingly growing. However, with the relaxation of moore's law, microelectronic chips begin to encounter performance bottlenecks, and currently, optical chips with advantages of high bandwidth, low loss, small size and the like are regarded as important supplements of microelectronic chips, and a feasible solution is provided for application scenes such as optical interconnection, optical computation and the like.
With the continuous development of optical chip technology, integrated photonic devices are not limited to a single layer, and often different optical waveguide layers are required to realize different functions, namely, three-dimensional integrated photonic chips. At this time, it is very important to realize efficient interconnection and interworking of optical signals between different optical waveguides, unlike electrical signals in microelectronic chips, optical signals in optical chips cannot directly realize low-loss vertical interconnection, and need to be gradually coupled from one layer to another layer by means of evanescent coupling, which is called interlayer optical coupling. The existing interlayer optical coupling structure generally only considers a Mode of a single polarization state, namely a transverse electric Mode (TRANSVERSE ELECTRIC Mode) or a transverse magnetic Mode (TRANSVERSE MAGNETIC Mode), and because the transverse electric Mode and the transverse magnetic Mode have different Mode field distributions, an interlayer coupler designed for the transverse electric Mode generally has larger loss for the transverse magnetic Mode, so that the interlayer coupler cannot be applied to communication or data center links.
Therefore, how to provide an interlayer optical coupler independent of polarization, which supports the transmission of the transverse electric mode and the transverse magnetic mode, and has extremely low interlayer coupling loss to the transverse electric mode and the transverse magnetic mode, is a technical problem to be solved by those skilled in the art.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a polarization independent interlayer optical coupler for solving the problem that the optical coupler in the prior art cannot achieve low coupling loss for both the transverse electric mode and the transverse magnetic mode.
To achieve the above and other related objects, the present invention provides a polarization independent interlayer optical coupler comprising:
a first waveguide layer;
A second waveguide layer located above the first waveguide layer in a vertical direction, at least a portion of the second waveguide layer being located at one side of the first waveguide layer in a horizontal direction;
A buffered waveguide layer, in a vertical direction, between the first waveguide layer and the second waveguide layer, the first waveguide layer overlapping the buffered waveguide layer to form a first coupling region, and the second waveguide layer overlapping the buffered waveguide layer to form a second coupling region, in a vertical direction projection;
The width of the first waveguide layer in the first coupling region tends to decrease, the width of the buffer waveguide layer in the first coupling region tends to increase, and the width of the buffer waveguide layer in the second coupling region tends to decrease, in the horizontal direction and in the direction from the first waveguide layer to the second waveguide layer.
Optionally, the effective thickness of the first waveguide layer is greater than the effective thickness of the second waveguide layer, and the effective thickness of the buffered waveguide layer is between the effective thickness of the first waveguide layer and the effective thickness of the second waveguide layer; or the effective thickness of the second waveguide layer is greater than the effective thickness of the first waveguide layer, and the effective thickness of the buffered waveguide layer is between the effective thickness of the first waveguide layer and the effective thickness of the second waveguide layer.
Optionally, the width of the first waveguide layer in the first coupling region decreases linearly, or the width of the first waveguide layer in the first coupling region decreases non-linearly; the width of the buffer waveguide layer in the first coupling region has a linear increasing trend, or the width of the buffer waveguide layer in the first coupling region has a nonlinear increasing trend; the width of the buffer waveguide layer in the second coupling region is in a linear decreasing trend, or the width of the buffer waveguide layer in the second coupling region is in a nonlinear decreasing trend; the width of the second waveguide layer in the second coupling region has a linear increasing trend, or the width of the second waveguide layer in the second coupling region has a nonlinear increasing trend.
Optionally, the materials of the first waveguide layer, the second waveguide layer and the buffer waveguide layer include one or more of silicon, silicon nitride, silicon oxynitride, lithium niobate, aluminum nitride and silicon carbide.
Optionally, the buffered waveguide layer includes a first buffered waveguide layer, a second buffered waveguide layer, … …, and an nth buffered waveguide layer, N is an integer greater than or equal to 2, in a vertical direction, the second buffered waveguide layer is located above the first buffered waveguide layer, … …, the nth buffered waveguide layer is located above the nth buffered waveguide layer, in a vertical direction projection, a left end portion of the first buffered waveguide layer overlaps the first waveguide layer, a right end portion of the first buffered waveguide layer overlaps a left end portion of the second buffered waveguide layer, … …, a left end portion of the nth buffered waveguide layer overlaps a right end portion of the N-1 buffered waveguide layer, a right end portion of the nth buffered waveguide layer overlaps the second waveguide layer, and a width change trend of the left end portion in each buffered waveguide layer is opposite to a width change trend of the right end portion.
Optionally, the semiconductor device further comprises a substrate, an oxygen-buried layer and an upper cladding layer, wherein the oxygen-buried layer is located above the substrate in a vertical direction, and the upper cladding layer is located above the oxygen-buried layer, and at least one part of the first waveguide layer, the second waveguide layer and the buffer waveguide layer is located in the upper cladding layer.
The present invention also provides a polarization independent interlayer optical coupler comprising:
a first waveguide layer;
the second waveguide layer is positioned above the first waveguide layer in the vertical direction, the second waveguide layer and the first waveguide layer are overlapped to form an interlayer coupling region in the vertical direction, the width of the first waveguide layer in the interlayer coupling region tends to be smaller in the horizontal direction and the direction from the first waveguide layer to the second waveguide layer, and the width of the second waveguide layer in the interlayer coupling region tends to be larger in the horizontal direction and the direction from the first waveguide layer to the second waveguide layer;
at least one of the first waveguide layer and the second waveguide layer has a thickness decreasing in a width decreasing direction in the interlayer coupling region.
Optionally, in a direction that is horizontal and directed by the first waveguide layer towards the second waveguide layer, the thickness of the first waveguide layer in the interlayer coupling region tends to decrease and/or the thickness of the second waveguide layer in the interlayer coupling region tends to increase.
Optionally, the width of the first waveguide layer in the interlayer coupling region decreases linearly, or the width of the first waveguide layer in the interlayer coupling region decreases non-linearly; the width of the second waveguide layer in the interlayer coupling region has a linear increasing trend, or the width of the second waveguide layer in the interlayer coupling region has a nonlinear increasing trend.
Optionally, the semiconductor device further comprises a substrate, an oxygen-buried layer and an upper cladding layer, wherein the oxygen-buried layer is located above the substrate in the vertical direction, and the upper cladding layer is located above the oxygen-buried layer, and at least one part of the first waveguide layer and the second waveguide layer is located in the upper cladding layer.
As described above, in the polarization independent interlayer optical coupler of the present invention, in the horizontal direction and in the direction from the first waveguide layer to the second waveguide layer, the width of the first waveguide layer in the coupling region tends to decrease, the width of the second waveguide layer in the coupling region tends to increase, and a buffer waveguide layer is introduced into the first waveguide layer and the second waveguide layer, or a thickness gradient is introduced into at least one of the first waveguide layer and the second waveguide layer, so that the transmission of the transverse electric mode and the transverse magnetic mode can be simultaneously supported, and the interlayer coupling loss to both the transverse electric mode and the transverse magnetic mode is extremely low.
Drawings
Fig. 1 is a perspective view of a polarization independent interlayer optical coupler according to a first embodiment of the present invention.
Fig. 2 shows a cross-sectional view of a polarization independent interlayer optical coupler in accordance with a first embodiment of the present invention.
Fig. 3 is a top view of a polarization independent interlayer optical coupler according to a first embodiment of the present invention.
FIG. 4 shows a normalized electric field amplitude distribution of transverse electric mode at a wavelength of 1.55 μm in the first embodiment of the present invention.
FIG. 5 shows a normalized electric field amplitude distribution of transverse magnetic mode at a wavelength of 1.55 μm in the first embodiment of the present invention.
FIG. 6 is a graph showing the variation of coupling loss at a wavelength in the range of 1.5-1.6 μm in the first embodiment of the present invention.
Fig. 7 is a perspective view of a polarization independent interlayer optical coupler according to a second embodiment of the present invention.
Fig. 8 shows a cross-sectional view of a polarization independent interlayer optical coupler in accordance with a second embodiment of the present invention.
Fig. 9 is a top view of a polarization independent interlayer optical coupler according to a second embodiment of the present invention.
FIG. 10 shows a normalized electric field amplitude distribution of transverse electric mode at a wavelength of 1.55 μm in the second embodiment of the present invention.
FIG. 11 shows a normalized electric field amplitude distribution of transverse magnetic mode at a wavelength of 1.55 μm in the second embodiment of the present invention.
FIG. 12 is a graph showing the variation of coupling loss at a wavelength in the range of 1.5-1.6 μm in the second embodiment of the present invention.
Reference numerals illustrate: 1-substrate, 2-buried oxide layer, 3-upper cladding layer, 4-first waveguide layer, 5-second waveguide layer, 6-buffer waveguide layer, 7-first coupling region, 8-second coupling region, 9-first waveguide layer, 10-second waveguide layer, 11-interlayer coupling region.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention.
Please refer to fig. 1 to 12. It should be noted that, the illustrations provided in the present embodiment merely illustrate the basic concept of the present invention by way of illustration, and only the components related to the present invention are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.
Example 1
The present embodiment provides a polarization independent interlayer optical coupler, referring to fig. 1 to 3, which includes a first waveguide layer 4, a second waveguide layer 5 and a buffer waveguide layer 6, wherein the second waveguide layer 5 is located above the first waveguide layer 4 in a vertical direction (z-direction), and at least a portion of the second waveguide layer 5 is located at one side of the first waveguide layer 4 in a horizontal direction (x-direction); in the vertical direction, the buffered waveguide layer 6 is located between the first waveguide layer 4 and the second waveguide layer 5, and in the projection in the vertical direction, the first waveguide layer 4 overlaps with the buffered waveguide layer 6 to form a first coupling region 7, and the second waveguide layer 5 overlaps with the buffered waveguide layer 6 to form a second coupling region 8; wherein in a horizontal direction and in a direction (x-direction) from the first waveguide layer 4 to the second waveguide layer 5, the width of the first waveguide layer 4 in the first coupling region 7 tends to decrease, the width of the buffer waveguide layer 6 in the first coupling region 7 tends to increase, the width of the buffer waveguide layer 6 in the second coupling region 8 tends to decrease, and the width of the second waveguide layer 5 in the second coupling region 8 tends to increase.
As an example, the polarization-independent interlayer optical coupler further comprises a substrate 1, an oxygen-buried layer 2 and an upper cladding layer 3, the oxygen-buried layer 2 being located above the substrate 1 and the upper cladding layer 3 being located above the oxygen-buried layer 2 in a vertical direction (z-direction), wherein at least a part of the first waveguide layer 4, the second waveguide layer 5 and the buffer waveguide layer 6 is located in the upper cladding layer 3. Specifically, in the present embodiment, the first waveguide layer 4, the second waveguide layer 5, and the buffered waveguide layer 6 are all located in the upper cladding layer 3, and in other examples, the first waveguide layer 4 and the buffered waveguide layer 6 may be located in the buried oxide layer 2, the second waveguide layer 5 may be located in the upper cladding layer 3, or the first waveguide layer 4 may be located in the buried oxide layer 2, and the buffered waveguide layer 6 and the second waveguide layer 5 may be located in the upper cladding layer 3, which is not limited to the present embodiment.
As an example, the substrate 1 may include a silicon substrate or a silicon oxide substrate, the material of the buried oxide layer 2 may include silicon oxide, and the material of the upper cladding layer 3 may include silicon oxide.
As an example, the first waveguide layer 4, the second waveguide layer 5, and the buffered waveguide layer 6 each use a high refractive index contrast material including silicon, silicon nitride, silicon oxynitride, lithium niobate, aluminum nitride, silicon carbide, and the like. In this embodiment, for convenience of processing, the first waveguide layer 4, the second waveguide layer 5, and the buffered waveguide layer 6 are made of the same material; in other examples, the first waveguide layer 4, the second waveguide layer 5, and the buffered waveguide layer 6 may be made of different materials, which is not limited to the present embodiment.
As an example, to achieve polarization-independent interlayer coupling, the effective thickness of the buffered waveguide layer 6 is typically between the effective thickness of the first waveguide layer 4 and the effective thickness of the second waveguide layer 5, when an optical field enters the first coupling region 7 first during the coupling of the optical field from the first waveguide layer 4 to the second waveguide layer 5, the optical field will be coupled from the first waveguide layer 4 to the buffered waveguide layer 6, in the first coupling region 7, the waveguide width of the first waveguide layer 4 gradually becomes smaller in the x-direction, and the width of the buffered waveguide layer 6 gradually becomes larger, and the optical field is nearly adiabatically coupled from the first waveguide layer 4 to the buffered waveguide layer 6; then, the optical field enters the second coupling region 8 to be coupled from the buffered waveguide layer 6 to the second waveguide layer 5, in the second coupling region 8, the waveguide width of the buffered waveguide layer 6 gradually becomes smaller and the width of the second waveguide layer 5 gradually becomes larger in the x direction, the optical field from the buffered waveguide layer 6 to the second waveguide layer 5 completes near adiabatic coupling, and thus the optical field as a whole realizes interlayer coupling from the first waveguide layer 4 to the second waveguide layer 5.
As an example, the effective thickness H is described as:
……（1）
Wherein, ，/>，N c denotes the upper cladding refractive index, n s denotes the buried oxide layer refractive index, n f denotes the waveguide refractive index, n eff denotes the waveguide effective refractive index, ε c denotes the upper cladding relative dielectric constant, ε s denotes the buried oxide layer relative dielectric constant, ε f denotes the waveguide relative dielectric constant. When the first waveguide layer 4, the second waveguide layer 5 and the buffered waveguide layer 6 are made of the same material, the physical thickness of the buffered waveguide layer 6 is between the physical thickness of the first waveguide layer 4 and the physical thickness of the second waveguide layer 5.
In other examples, it is also possible to provide that the optical field is coupled from the second waveguide layer 5 into the first waveguide layer 4, that the optical field first enters the second coupling region 8 to be coupled from the second waveguide layer 5 into the buffered waveguide layer 6, and that the optical field then enters the first coupling region 7 to be coupled from the buffered waveguide layer 6 into the first waveguide layer 4.
As an example, the principle of evanescent coupling is utilized when an optical signal is transmitted between layers, in each coupling region, the waveguide width of one waveguide layer gradually decreases, the waveguide width of the other waveguide layer gradually increases, and the optical signal is coupled to the waveguide layer with the increased width; in the coupling region, the waveguide width is graded in a near adiabatic manner to maintain extremely low transmission losses.
As an example, in the x-direction, in the first coupling region 7, the first waveguide layer 4 decreases in width non-linearly, and the buffered waveguide layer 6 increases in width non-linearly; in the second coupling region 8, the width of the buffered waveguide layer 6 decreases non-linearly, and the width of the second waveguide layer 5 increases non-linearly. In other examples, the width of the first waveguide layer 4 in the first coupling region 7 may be linearly decreased, the width of the buffered waveguide layer 6 in the first coupling region 7 may be linearly increased, and the width of the buffered waveguide layer 6 in the second coupling region 8 may be linearly decreased, and the width of the second waveguide layer 5 in the second coupling region 8 may be linearly increased, which is not limited to the present embodiment. Generally, a tapered waveguide that varies non-linearly may achieve adiabatic coupling over a shorter length than a tapered waveguide that varies linearly.
It should be noted that, the waveguide width described in the present embodiment is in a trend of decreasing, which means that the waveguide width is smaller as a whole, and the local waveguide width may be kept unchanged or slightly increased, which also belongs to the protection scope of the present patent; similarly, the waveguide width described in the present embodiment tends to increase, which means that the waveguide width is increased as a whole, and the local waveguide width may be kept unchanged or slightly reduced, which also belongs to the protection scope of the present patent.
Specifically, taking a silicon nitride waveguide as an example, the materials of the first waveguide layer 4, the second waveguide layer 5 and the buffer waveguide layer 6 are all silicon nitride, wherein the thickness of the first waveguide layer 4 is 800 nm, the thickness of the second waveguide layer 5 is 250 nm, the thickness of the buffer waveguide layer 6 is 400nm, the distance between the first waveguide layer 4 and the buffer waveguide layer 6 is 400nm, the distance between the buffer waveguide layer 6 and the second waveguide layer 5 is 500 nm, the length of the first coupling region 7 is 240 μm, the width of the first waveguide layer 4 in the first coupling region 7 is linearly changed from 800 nm to 150 nm, the width of the buffer waveguide layer 6 is linearly changed from 150 nm to 2100 nm, the length of the second coupling region 8 is 300 μm, the width of the buffer waveguide layer 6 in the second coupling region 8 is linearly changed from nm to 150 nm, and the width of the second waveguide layer 5 in the first coupling region 7 is linearly changed from 2100 to 2500. Referring to fig. 4, the coupling loss of the transverse electric mode is about 0.03 dB when the wavelength is 1.55 μm, and referring to fig. 5, the coupling loss of the transverse magnetic mode is about 0.03 dB when the wavelength is 1.55 μm, which indicates that the interlayer optical coupler of the embodiment supports the transmission of the transverse electric mode and the transverse magnetic mode at the same time, and has extremely low interlayer coupling loss for both the transverse electric mode and the transverse magnetic mode; referring to fig. 6, the wavelength is in the range of 1.5-1.6 μm, and the transverse electric mode and the transverse magnetic mode have extremely low interlayer coupling loss, which indicates that the interlayer optical coupler of the embodiment can realize polarization independent low-loss interlayer coupling in a broadband range.
As an example, in this embodiment, the buffered waveguide layer 6 is provided with only one layer, in other examples, in order to better isolate the first waveguide layer 4 from the second waveguide layer 5, more buffered waveguide layers may be provided, for example, a first buffered waveguide layer, a second buffered waveguide layer, … …, an nth buffered waveguide layer, N is an integer of ≡2, in the vertical direction (z-direction), the second buffered waveguide layer is located above the first buffered waveguide layer, … …, the nth buffered waveguide layer is located above the nth buffered waveguide layer, in the projection in the vertical direction, the left end portion of the first buffered waveguide layer overlaps with the first waveguide layer, the right end portion of the first buffered waveguide layer overlaps with the left end portion of the second buffered waveguide layer, … …, the left end portion of the nth buffered waveguide layer overlaps with the right end portion of the N-1 buffered waveguide layer, the right end portion of the nth buffered waveguide layer overlaps with the second waveguide layer, and the width of each buffered waveguide layer changes in opposite directions.
By way of example, the ellipses in fig. 1 and 2 represent other waveguide devices to which the interlayer optical coupler is connected; in addition, the waveguides are illustrated as straight waveguides of symmetrical structure for convenience of description, and in other examples, may be provided as curved shapes of asymmetrical structures; and the width and thickness of the non-coupling region in the waveguide layer can also be varied as desired.
As an example, in the present embodiment, the second waveguide layer 5 is located entirely on one side of the first waveguide layer 4 in the horizontal direction, that is, on the projection in the vertical direction, the second waveguide layer 5 does not overlap with the first waveguide layer 4; in other examples, the second waveguide layer 5 may also be partially located on one side of the first waveguide layer 4 in the horizontal direction, i.e. in the vertical direction, and it is also within the scope of the present invention to partially overlap the second waveguide layer 5 with the first waveguide layer 4.
As described above, in the polarization independent interlayer optical coupler of this embodiment, the buffer waveguide layer is disposed between the first waveguide layer and the second waveguide layer, the width of the first waveguide layer in the first coupling region tends to decrease, the width of the buffer waveguide layer in the first coupling region tends to increase, the width of the buffer waveguide layer in the second coupling region tends to decrease, and the width of the second waveguide layer in the second coupling region tends to increase, so that the transmission of the transverse electric mode and the transverse magnetic mode can be simultaneously supported, and the interlayer coupling loss for both the transverse electric mode and the transverse magnetic mode is extremely low.
Example two
The present embodiment provides a polarization independent interlayer optical coupler, referring to fig. 7 to 9, the polarization independent interlayer optical coupler includes a first waveguide layer 9 and a second waveguide layer 10, the second waveguide layer 10 is located above the first waveguide layer 9 in a vertical direction (z direction), the second waveguide layer 10 overlaps the first waveguide layer 9 in a projection in the vertical direction to form an interlayer coupling region 11, the width of the first waveguide layer 9 in the interlayer coupling region 11 tends to decrease in a direction (x direction) from the first waveguide layer 9 to the second waveguide layer 10 in a horizontal direction, and the width of the second waveguide layer 10 in the interlayer coupling region 11 tends to increase in a direction (x direction); wherein, in the interlayer coupling region 11, at least one of the first waveguide layer 9 and the second waveguide layer 10 has a thickness decreasing in a width decreasing direction thereof.
As an example, the polarization-independent interlayer optical coupler further comprises a substrate 1, an oxygen-buried layer 2 and an upper cladding layer 3, the oxygen-buried layer 2 being located above the substrate 1 and the upper cladding layer 3 being located above the oxygen-buried layer 2 in a vertical direction (z-direction), wherein at least a part of the first waveguide layer 9 and the second waveguide layer 10 is located in the upper cladding layer 3. Specifically, in this embodiment, the first waveguide layer 9 and the second waveguide layer 10 are both located in the upper cladding layer 3, and in other examples, the first waveguide layer 9 may be located in the oxygen-buried layer 2, and the second waveguide layer 10 may be located in the upper cladding layer 3, which is not limited to this embodiment.
As an example, the substrate 1 may include a silicon substrate or a silicon oxide substrate, the material of the buried oxide layer 2 may include silicon oxide, and the material of the upper cladding layer 3 may include silicon oxide.
As an example, the first waveguide layer 9 and the second waveguide layer 10 each use a high refractive index contrast material including silicon, silicon nitride, silicon oxynitride, lithium niobate, aluminum nitride, silicon carbide, and the like. In this embodiment, for convenience of processing, the first waveguide layer 9 and the second waveguide layer 10 are made of the same material; in other examples, the first waveguide layer 9 and the second waveguide layer 10 may be made of different materials, which is not limited to the present embodiment.
As an example, in order to achieve polarization-independent interlayer coupling, in the interlayer coupling region 11, at least one of the first waveguide layer 9 and the second waveguide layer 10 gradually decreases in thickness in the width-decreasing direction thereof. In the present embodiment, the thickness of the first waveguide layer 9 is set to be gradually reduced, the thickness of the second waveguide layer 10 is set to be constant, and the pitch between the first waveguide layer 9 and the second waveguide layer 10 (i.e., the pitch between the upper surface of the first waveguide layer 9 and the lower surface of the second waveguide layer 10) is gradually increased in the thickness reduction direction (x-direction) along the first waveguide layer 9. In another example, the thickness of the first waveguide layer 9 may be set constant, and in the interlayer coupling region 11, the thickness of the second waveguide layer 10 gradually decreases in the-x direction; or in the interlayer coupling region 11, the thickness of the first waveguide layer 9 is gradually reduced in the x-direction while the thickness of the second waveguide layer 10 is gradually reduced in the-x-direction.
As an example, in the interlayer coupling region 11, the waveguide width of the first waveguide layer 9 becomes gradually smaller and the waveguide width of the second waveguide layer 10 becomes gradually larger in the x-direction, and the optical field is nearly adiabatically coupled from the first waveguide layer 9 to the second waveguide layer 10.
As an example, the principle of evanescent coupling is used when an optical signal is transmitted between layers, and in the interlayer coupling region 11, the waveguide width of one waveguide layer gradually decreases, the waveguide width of the other waveguide layer gradually increases, and the optical signal is coupled to the waveguide layer with the increased width; in the coupling region, the waveguide width is graded in a near adiabatic manner to maintain extremely low transmission losses.
As an example, in the x-direction, in the interlayer coupling region 11, the width of the first waveguide layer 9 decreases non-linearly, and the width of the second waveguide layer 10 increases non-linearly. In other examples, the width of the first waveguide layer 9 in the interlayer coupling region 11 may be linearly decreased, and the width of the second waveguide layer 10 may be linearly increased, and the non-linearly-changed tapered waveguide may be adiabatically coupled in a shorter length than the linearly-changed tapered waveguide without being limited to the present embodiment. Similarly, in the interlayer coupling region 11, the thickness variation of the waveguide layer may be a linear variation or a nonlinear variation, which is selected according to the actual requirement.
It should be noted that, the waveguide width and the thickness described in the present embodiment are reduced, which means that the waveguide width or thickness is reduced as a whole, and the local waveguide width or thickness may be kept unchanged or slightly increased, which also belongs to the protection scope of the present patent; similarly, the waveguide width described in the present embodiment tends to increase, which means that the waveguide width is increased as a whole, and the local waveguide width may be kept unchanged or slightly reduced, which also belongs to the protection scope of the present patent.
Specifically, taking a silicon nitride waveguide as an example, the first waveguide layer 9 and the second waveguide layer 10 are both made of silicon nitride, wherein the thickness of the first waveguide layer 9 is 800 nm, the thickness of the second waveguide layer 10 is 250 nm, when no thickness gradient is introduced, the interval between the first waveguide layer 9 and the second waveguide layer 10 (i.e., the interval between the upper surface of the first waveguide layer 9 and the lower surface of the second waveguide layer 10) is 300 nm, the length of the interlayer coupling region 11 is 200 μm, the width of the first waveguide layer 9 in the interlayer coupling region 11 is linearly changed from 800 nm to 150nm, the thickness of the first waveguide layer 9 is linearly changed from 800 nm to 150nm, and the width of the second waveguide layer 10 is linearly changed from 150nm to 1400 nm. Referring to fig. 10, the coupling loss of the transverse electric mode is about 0.01 dB when the wavelength is 1.55 μm, and referring to fig. 11, the coupling loss of the transverse magnetic mode is about 0.014 dB when the wavelength is 1.55 μm, which indicates that the interlayer optical coupler of the embodiment supports the transmission of the transverse electric mode and the transverse magnetic mode simultaneously, and has extremely low interlayer coupling loss for both the transverse electric mode and the transverse magnetic mode; referring to fig. 12, the wavelengths are in the range of 1.5-1.6 μm, and the transverse electric mode and the transverse magnetic mode have extremely low interlayer coupling loss, which indicates that the interlayer optical coupler of the embodiment can realize polarization independent low-loss interlayer coupling in a broadband range.
By way of example, the ellipses in fig. 7 and 8 represent other waveguide devices to which the interlayer optical coupler is connected; in addition, the waveguides are illustrated as straight waveguides of symmetrical structure for convenience of description, and in other examples, may be provided as curved shapes of asymmetrical structures; and the width and thickness of the non-coupling region in the waveguide layer can also be varied as desired.
As an example, the present invention is not limited to the scheme described in the first or second embodiment alone, and the two schemes may be flexibly combined to achieve a desired interlayer coupling effect.
In summary, in the polarization independent interlayer optical coupler of the present invention, in the horizontal direction and in the direction from the first waveguide layer to the second waveguide layer, the width of the first waveguide layer in the coupling region tends to decrease, the width of the second waveguide layer in the coupling region tends to increase, and a buffer waveguide layer is introduced into the first waveguide layer and the second waveguide layer, or a thickness gradient is introduced into at least one of the first waveguide layer and the second waveguide layer, so that the transmission of the transverse electric mode and the transverse magnetic mode can be simultaneously supported, and the interlayer coupling loss to both the transverse electric mode and the transverse magnetic mode is extremely low. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.
Claims (10)
1. A polarization independent interlayer optical coupler, comprising:
a first waveguide layer;
A second waveguide layer located above the first waveguide layer in a vertical direction, at least a portion of the second waveguide layer being located at one side of the first waveguide layer in a horizontal direction;
A buffered waveguide layer, in a vertical direction, between the first waveguide layer and the second waveguide layer, the first waveguide layer overlapping the buffered waveguide layer to form a first coupling region, and the second waveguide layer overlapping the buffered waveguide layer to form a second coupling region, in a vertical direction projection;
The width of the first waveguide layer in the first coupling region tends to decrease, the width of the buffer waveguide layer in the first coupling region tends to increase, and the width of the buffer waveguide layer in the second coupling region tends to decrease, in the horizontal direction and in the direction from the first waveguide layer to the second waveguide layer.
2. The polarization independent interlayer optical coupler of claim 1, wherein: the effective thickness of the first waveguide layer is greater than the effective thickness of the second waveguide layer, and the effective thickness of the buffer waveguide layer is between the effective thickness of the first waveguide layer and the effective thickness of the second waveguide layer; or the effective thickness of the second waveguide layer is greater than the effective thickness of the first waveguide layer, and the effective thickness of the buffered waveguide layer is between the effective thickness of the first waveguide layer and the effective thickness of the second waveguide layer.
3. The polarization independent interlayer optical coupler of claim 1, wherein: the width of the first waveguide layer in the first coupling region is in a linear decreasing trend, or the width of the first waveguide layer in the first coupling region is in a nonlinear decreasing trend; the width of the buffer waveguide layer in the first coupling region has a linear increasing trend, or the width of the buffer waveguide layer in the first coupling region has a nonlinear increasing trend; the width of the buffer waveguide layer in the second coupling region is in a linear decreasing trend, or the width of the buffer waveguide layer in the second coupling region is in a nonlinear decreasing trend; the width of the second waveguide layer in the second coupling region has a linear increasing trend, or the width of the second waveguide layer in the second coupling region has a nonlinear increasing trend.
4. The polarization independent interlayer optical coupler of claim 1, wherein: the materials of the first waveguide layer, the second waveguide layer and the buffer waveguide layer comprise one or more of silicon, silicon nitride, silicon oxynitride, lithium niobate, aluminum nitride and silicon carbide.
5. The polarization independent interlayer optical coupler of claim 1, wherein: the buffered waveguide layer comprises a first buffered waveguide layer, a second buffered waveguide layer, … … and an Nth buffered waveguide layer, N is an integer larger than or equal to 2, in the vertical direction, the second buffered waveguide layer is positioned above the first buffered waveguide layer, … … and the Nth buffered waveguide layer is positioned above the N-1 buffered waveguide layer, in the vertical direction, the left end part of the first buffered waveguide layer is overlapped with the first waveguide layer, the right end part of the first buffered waveguide layer is overlapped with the left end part of the second buffered waveguide layer, … … and the left end part of the Nth buffered waveguide layer is overlapped with the right end part of the N-1 buffered waveguide layer, and the width change trend of the left end part and the width change trend of the right end part in each buffered waveguide layer are opposite.
6. The polarization independent interlayer optical coupler of any of claims 1 to 5, wherein: the semiconductor device further comprises a substrate, an oxygen-buried layer and an upper cladding layer, wherein the oxygen-buried layer is located above the substrate in the vertical direction, and the upper cladding layer is located above the oxygen-buried layer, and at least one part of the first waveguide layer, the second waveguide layer and the buffer waveguide layer is located in the upper cladding layer.
7. A polarization independent interlayer optical coupler, comprising:
a first waveguide layer;
the second waveguide layer is positioned above the first waveguide layer in the vertical direction, the second waveguide layer and the first waveguide layer are overlapped to form an interlayer coupling region in the vertical direction, the width of the first waveguide layer in the interlayer coupling region tends to be smaller in the horizontal direction and the direction from the first waveguide layer to the second waveguide layer, and the width of the second waveguide layer in the interlayer coupling region tends to be larger in the horizontal direction and the direction from the first waveguide layer to the second waveguide layer;
at least one of the first waveguide layer and the second waveguide layer has a thickness decreasing in a width decreasing direction in the interlayer coupling region.
8. The polarization independent interlayer optical coupler of claim 7, wherein: in a direction that is horizontal and directed by the first waveguide layer toward the second waveguide layer, the thickness of the first waveguide layer in the interlayer coupling region tends to decrease, and/or the thickness of the second waveguide layer in the interlayer coupling region tends to increase.
9. The polarization independent interlayer optical coupler of claim 7, wherein: the width of the first waveguide layer in the interlayer coupling region is in a linear decreasing trend, or the width of the first waveguide layer in the interlayer coupling region is in a nonlinear decreasing trend; the width of the second waveguide layer in the interlayer coupling region has a linear increasing trend, or the width of the second waveguide layer in the interlayer coupling region has a nonlinear increasing trend.
10. The polarization independent interlayer optical coupler of any of claims 7 to 9, wherein: the semiconductor device further comprises a substrate, an oxygen-buried layer and an upper cladding layer, wherein the oxygen-buried layer is located above the substrate in the vertical direction, the upper cladding layer is located above the oxygen-buried layer, and at least one part of the first waveguide layer and the second waveguide layer is located in the upper cladding layer.
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