CN115933052A - Optical waveguide coupler and method for manufacturing optical waveguide coupler - Google Patents
Optical waveguide coupler and method for manufacturing optical waveguide coupler Download PDFInfo
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- 230000003287 optical effect Effects 0.000 title claims abstract description 74
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 23
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- 239000000758 substrate Substances 0.000 claims abstract description 64
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- 238000005859 coupling reaction Methods 0.000 claims abstract description 49
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 16
- 229910052710 silicon Inorganic materials 0.000 description 16
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- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 10
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Abstract
The present application relates to an optical waveguide coupler and a method of manufacturing an optical waveguide coupler. An optical waveguide coupler is used for coupling with an optical fiber, and comprises a substrate and a high-refractive-index waveguide, wherein the high-refractive-index waveguide is formed on the substrate and extends along a first direction; the high refractive index waveguide has a first end portion and a second end portion disposed opposite to each other in a first direction. The first end is closer to the optical fiber than the second end. The thickness of the first end part of the high-refractive-index waveguide is a first preset value, and the size of the first end part of the high-refractive-index waveguide along the second direction is a second preset value, so that the first end part can be in TE fundamental mode coupling with the optical fiber. The optical waveguide coupler is simple in device, easy to manufacture and provided with the function of polarizing the end face coupler.
Description
Technical Field
The present disclosure relates to the field of coupler technologies, and in particular, to an optical waveguide coupler and a method for manufacturing the optical waveguide coupler.
Background
The conventional end-face coupler is generally used for coupling of multiple polarization modes, and in single polarization mode application, a polarization conversion module is required to be added at the back end of the conventional end-face coupler to realize single polarization mode application. However, the introduction of the polarization conversion module increases the complexity of the device and the difficulty of manufacturing.
Disclosure of Invention
Therefore, it is necessary to provide an optical waveguide coupler with high efficiency and polarization effect and a method for manufacturing the optical waveguide coupler, aiming at the problem that the complexity and the manufacturing difficulty of the device are increased by adding a polarization conversion module to the rear end of the conventional end-face coupler in the application of a single polarization mode.
According to an aspect of the present application, there is provided an optical waveguide coupler for coupling with an optical fiber, the optical waveguide coupler comprising:
a substrate; and
a high refractive index waveguide formed on the substrate and extending in a first direction; the high refractive index waveguide has a first end portion and a second end portion disposed opposite to each other in a first direction; the first end is closer to the optical fiber than the second end;
a low index cladding overlying to the high index waveguide and in contact with the substrate;
the thickness of the first end part of the high-refractive-index waveguide is a first preset value, and the size of the first end part of the high-refractive-index waveguide along a second direction is a second preset value, so that the first end part can be in TE fundamental mode coupling with the optical fiber;
wherein the first direction and the second direction are perpendicular to each other.
In one embodiment, the first preset value is less than or equal to 120nm, and the second preset value is greater than or equal to 250nm.
In one embodiment, the optical waveguide coupler further comprises a low index cladding layer overlying the high index waveguide and in contact with the substrate;
an absolute difference between a refractive index of the low-index cladding and a refractive index of the core of the optical fiber is smaller than an absolute difference between a refractive index of the high-index waveguide and a refractive index of the core of the optical fiber.
In one embodiment, the substrate comprises a base and an isolation layer which are arranged in a stacked manner;
the high-refractive-index waveguide is arranged on the isolation layer;
the low-refractive-index cladding layer covers the high-refractive-index waveguide and is in contact with the isolation layer;
the low-refractive-index cladding layer and the isolation layer are made of the same material.
In one embodiment, the high refractive index waveguide includes a first portion and a second portion connected in series and extending in a first direction;
the first end part is arranged at one end of the first part far away from the second part, and the second end part is arranged at one end of the second part far away from the first part;
the thickness of the first portion gradually increases from the first end to the second end along the first direction;
the thickness of the second portion remains constant along the first direction.
In one embodiment, a dimension of the first portion along the first direction is greater than or equal to 120 μm.
In one embodiment, the low refractive index cladding comprises a third portion and a fourth portion connected in series;
the third part covers the first part and is in contact with the substrate;
the fourth portion overlies the second portion.
In one embodiment, the first end of the high index waveguide is coupled to the optical fiber and a center of the first end coincides with a central axis of a core of the optical fiber.
According to another aspect of the present application, there is provided a method of manufacturing an optical waveguide coupler, including the steps of:
providing a substrate;
forming a high refractive index waveguide extending in a first direction on the substrate;
forming a low index cladding overlying the high index waveguide and in contact with the substrate;
polishing or cracking to make the thickness of the first end of the high-refractive-index waveguide be a first preset value, and the size of the first end of the high-refractive-index waveguide along the second direction be a second preset value, so that the first end can be coupled with the optical fiber in a TE fundamental mode;
wherein the high refractive index waveguide has the first end portion and the second end portion disposed opposite to each other in a first direction;
the first end is closer to the optical fiber than the second end;
the first direction and the second direction are perpendicular to each other.
In one embodiment, the substrate includes a substrate and an isolation layer, which are stacked, and the forming of the high-refractive-index waveguide extending in the first direction on the substrate specifically includes:
forming a high refractive index waveguide layer on the isolation layer;
thinning the surface of the high-refractive-index waveguide layer to gradually reduce the thickness of the high-refractive-index waveguide layer in the first direction;
and etching the high-refractive-index waveguide layer to etch the high-refractive-index waveguide layer into the high-refractive-index waveguide with a ridge structure or a line structure.
According to the optical waveguide coupler and the preparation method of the optical waveguide coupler, the thickness of the first end part of the high-refractive-index waveguide is set to be the first preset value, so that the TM fundamental mode cannot be effectively bound by the high-refractive-index waveguide in the process of transmitting optical fibers to the high-refractive-index waveguide, single-mode polarization can be realized, namely only the TE fundamental mode in the high-refractive-index waveguide is excited for coupling, and the TM fundamental mode is cut off 0 The requirements of (a).
Drawings
Fig. 1 is a schematic structural diagram of an optical waveguide coupler according to an embodiment of the present application;
FIG. 2 is a side cross-sectional view of an optical waveguide coupler according to an embodiment of the present application;
FIGS. 3a-3c are cross-sectional views of an optical fiber in a section CS1 and an optical waveguide coupler of an embodiment of the present application in a section CS2 and a section CS3, respectively;
FIG. 4 is a diagram of the mode fields of an optical fiber at the CS1 section and an optical waveguide coupler of an embodiment of the present application at the CS2 section and the CS3 plane, respectively;
FIG. 5 is a graph showing TE coupling efficiency from an optical fiber to a high-index waveguide as a function of the width and thickness of the high-index waveguide (the high-index waveguide is made of lithium niobate);
FIG. 6 is a graph showing the TM coupling efficiency from an optical fiber to a high index waveguide as a function of the width and thickness of the high index waveguide (the high index waveguide is made of lithium niobate);
FIG. 7 shows the TE coupling efficiency from the fiber to the high index waveguide as a function of the thickness of the low index cladding (the high index waveguide is lithium niobate);
FIG. 8 shows an optical waveguide coupler in TE in an embodiment of the present application 0 Side view (a) and top view (b) of the first waveguide in the mode (the high refractive index waveguide is made of lithium niobate);
FIG. 9 is a graph showing the effect of the offset of the center of the core of an optical fiber relative to the center of a high index waveguide on coupling loss in an optical waveguide coupler in an embodiment of the present application;
FIG. 10 is a graph showing the variation of optical waveguide coupler with wavelength in one embodiment of the present application;
FIG. 11 is a graph showing TE coupling efficiency from an optical fiber to a high-index waveguide as a function of the width and thickness of the high-index waveguide (the high-index waveguide is made of silicon);
FIG. 12 is a graph showing TE1 coupling efficiency from an optical fiber to a high-index waveguide as a function of the width and thickness of the high-index waveguide (the high-index waveguide is made of silicon);
FIG. 13 shows a side view (a) and a top view (b) of the optical waveguide coupler of another embodiment of the present application for the propagation of the optical field of the first waveguide section in the TE0 mode (the high index waveguide is made of silicon);
FIG. 14 is a graph showing the effect of the offset of the center of the core of an optical fiber relative to the center of a high index waveguide on coupling loss in an optical waveguide coupler according to another embodiment of the present application;
FIG. 15 is a graph showing the variation of optical waveguide coupler with wavelength in another embodiment of the present application;
FIG. 16 is a schematic flow chart illustrating a method of fabricating an optical waveguide coupler according to an embodiment of the present application;
FIG. 17 is a schematic flow chart illustrating a method of fabricating an optical waveguide coupler in an embodiment of the present application;
fig. 18a-18e show schematic diagrams of fabrication processes for an optical waveguide coupler in an embodiment of the present application.
In the figure: 10. an optical waveguide coupler; 110. a substrate; 111. a substrate; 112. an isolation layer; 113. a high refractive index waveguide layer; 120. a high refractive index waveguide; 1201. a first end portion; 1202. a second end portion; 121. a first portion; 122. a second guided band second portion; 130. a low refractive index cladding; 131. a third portion; 132. a fourth part; 20. an optical fiber; 21. a core.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present application more comprehensible, embodiments accompanying the present application are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. This application is capable of embodiment in many different forms than those described herein and those skilled in the art will be able to make similar modifications without departing from the spirit of the application and therefore the application is not limited to the specific embodiments disclosed below.
In the description of the present application, it is to be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the present application and for simplicity in description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the present application.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present application, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In this application, unless expressly stated or limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can include, for example, fixed connections, removable connections, or integral parts; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be interconnected within two elements or in a relationship where two elements interact with each other unless otherwise specifically limited. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.
In this application, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through intervening media. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. As used herein, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like are for purposes of illustration only and do not denote a single embodiment.
Fig. 1 shows a schematic structural diagram of an optical waveguide coupler 10 in an embodiment of the present application, fig. 2 shows a side sectional view of the optical waveguide coupler 10 in an embodiment of the present application, and fig. 3a-c are sectional views of an optical fiber 20 in a section CS1 and an optical waveguide coupler 10 in an embodiment of the present application in a section CS2 and a section CS3, respectively.
Referring to fig. 1-4, an optical waveguide coupler 10 for coupling with an optical fiber 20 is provided, the optical waveguide coupler 10 including a substrate 110, a high refractive index waveguide 120, and a low refractive index cladding 130.
The high refractive index waveguide 120 is formed on the substrate 110 along a first direction F 1 Extending, low index cladding 130 overlies high index waveguide 120 and is in contact with substrate 110. The high refractive index waveguide 120 has a first direction F 1 The first end portion 1201 and the second end portion 1202 are oppositely arranged, the first end portion 1201 is closer to the optical fiber 20 than the second end portion 1202, wherein the refractive index of the core 21 of the optical fiber 20 is between the refractive index of the high refractive index waveguide 120 and the refractive index of air, the thickness of the first end portion 1201 of the high refractive index waveguide 120 is smaller than that of the second end portion 1202 of the high refractive index waveguide 120, the thickness of the first end portion 1201 of the high refractive index waveguide 120 is a first preset value, and the first end portion 1201 of the high refractive index waveguide 120 is along the second direction F 2 Is a second preset value to enable TE fundamental mode coupling of the first end portion 1201 with the optical fiber 20.
The optical waveguide couplerWhen the combiner 10 is used, because the thickness of the first end portion 1201 of the high refractive index waveguide 120 is set to be the first preset value, the TM fundamental mode cannot be effectively bound by the high refractive index waveguide 120 in the process of transmitting the optical fiber 20 to the high refractive index waveguide 120, the single-mode polarization can be realized, that is, only the TE fundamental mode coupling in the high refractive index waveguide 120 is excited, and the TM fundamental mode is cut off, the end-face coupler has the polarization function, and the single-mode TE of various multi-electrical regulation and dispersion regulation devices is satisfied 0 The device stability is improved and the efficiency of coupling the high index waveguide 120 to the optical fiber is also improved.
In addition, the refractive index of the low-index cladding 130 is between the refractive index of the high-index waveguide 120 and the refractive index of air, so that the high-index waveguide 120 can effectively guide the optical fiber 20 to transmit in the TE mode, and leakage into the substrate 110 is reduced.
In some embodiments, the thickness of the first end portion 1201 of the high index waveguide 120 is smaller than the thickness of the second end portion 1202 of the high index waveguide 120, so that the thickness of the high index waveguide 120 tends to change, which is beneficial for improving the coupling efficiency of the optical waveguide coupler 10.
In some embodiments, referring to FIG. 2, the high index waveguide 120 includes a plurality of waveguides connected in series and oriented along a first direction F 1 A first portion 121 and a second portion 122 extending from each other, a first end portion 1201 is provided at an end of the first portion 121 remote from the second portion 122, and a second end portion 1202 is provided at an end of the second portion 122 remote from the first portion 121. Along a first direction F 1 The thickness of the first portion 121 gradually increases from the first end 1201 to the second end 1202. Along a first direction F 1 The thickness of the second portion 122 remains constant.
In the process of propagating the optical field in the first waveguide band described below, the thickness of the first portion 121 of the high refractive index waveguide 120 is gradually increased, the confinement capability to the optical field is enhanced, and through adiabatic evolution, the optical field is almost entirely localized in the high refractive index waveguide 120, thereby improving the coupling efficiency.
In some embodiments, referring to fig. 2 in combination with fig. 3b and 3c, the low refractive index cladding 130 includes a third portion 131 and a fourth portion 132 connected in series, the third portion 131 covering the first portion 121 and contacting the substrate 110, and the fourth portion 132 covering the second portion 122.
The optical waveguide coupler 10 includes a first waveguide section including a first portion 121, a third portion 131, and a portion of the isolation layer 112.
It will be appreciated that in the first direction F 1 The increasing thickness of the first portion 121 of the first waveguide segment increases the confinement capability for the optical field from the first end 1201 toward the second end 1202, and eventually the TE mode of the first end 1201 with the larger spot area is localized almost entirely in the second end 1202 of the high refractive index waveguide 120. In some embodiments, the absolute difference between the refractive index of low index cladding 130 and the refractive index of core 21 of optical fiber 20 is less than the absolute difference between the refractive index of high index waveguide 120 and the refractive index of core 21 of optical fiber 20.
Under the condition that the thickness of the first end portion 1201 of the high refractive index waveguide 120 is set to be a first preset value, the high refractive index waveguide 120 can effectively guide the optical fiber 20 to be coupled to the propagation of the TE0 mode of the first end portion 1201, leakage into the substrate 110 is reduced, and compared with the high refractive index waveguide 120, the low refractive index cladding 130 is closer to the refractive index of the optical fiber 20, so that the overlapping degree of the TE mode fields in the first end portion 1201 and the optical fiber 20 is high; in the process of transmitting the optical field in the first waveguide section, the thickness of the first part 121 of the high-refractive-index waveguide 120 is gradually increased, the constraint capacity on the optical field is enhanced, and finally, the optical field is almost entirely localized in the high-refractive-index waveguide 120 through adiabatic evolution, so that the coupling efficiency is improved.
In some embodiments, the first preset value is less than or equal to 120nm, the second preset value is greater than or equal to 250nm, and the first direction F 1 And a second direction F 2 Perpendicular to each other.
First direction F 1 Parallel to the length direction of the high refractive index waveguide 120, a second direction F 2 Parallel to the width direction of the high refractive index waveguide 120, then the high refractive index waveguide 120 is along the first direction F 1 Is the length of the high refractive index waveguide 120, the high refractive index waveguide 120 being along the second direction F 2 Is the size ofThe width of the high index waveguide 120.
The material of the high-index waveguide 120 may include, but is not limited to, lithium niobate and silicon to ensure TE-mode coupling of the first end portion 1201 of the high-index waveguide 120 with the optical fiber 20.
In some embodiments, referring to fig. 5-9, the high index waveguide 120 is lithium niobate, the low index cladding 130 is silicon dioxide, and the substrate 111 of the substrate 110 is silicon.
As shown in fig. 5, the low refractive index cladding 130 has a thickness of 2.6 μm, and when the thickness of the high refractive index waveguide 120 is less than 40nm, the high refractive index waveguide 120 cannot effectively confine the TE fundamental mode, and as shown in fig. 6, when the thickness of the high refractive index waveguide 120 is less than 80nm, the high refractive index waveguide 120 cannot effectively confine the TM fundamental mode. Therefore, when the first preset value may be less than or equal to 80nm and greater than 40nm, the first end portion 1201 of the high refractive index waveguide 120 and the optical fiber 20 may be used for TE fundamental mode coupling to achieve single mode polarization, and the width of the first end portion 1201 of the high refractive index waveguide 120 may meet the condition of deep ultraviolet lithography (for example, the width of the first end portion 1201 of the high refractive index waveguide 120 may be set to 1200 nm), which may save the manufacturing time and cost, have high repeatability, and are suitable for mass production. In particular, as shown in the embodiments of FIGS. 5-9, the high index waveguide 120 is oriented in the second direction F 2 Is 1200nm, the thickness of the first end portion 1201 of the high index waveguide 120 is 60nm, the coupling efficiency from the optical fiber 20 to the high index waveguide 120 can reach 96%, and the corresponding coupling loss is 0.18dB.
Referring to FIG. 5, the high refractive index waveguide 120 is along a second direction F 2 The larger the dimension of (a) is, in order to ensure the coupling efficiency of the optical fiber 20 to the high refractive index waveguide 120, the smaller the first preset value needs to be set, that is, the smaller the thickness of the first end portion 1201 of the high refractive index waveguide 120 is.
In other embodiments, the high refractive index waveguide 120 is made of lithium niobate, the low refractive index cladding 130 is made of silica, the substrate 111 of the substrate 110 is made of silicon, the first predetermined value is greater than 80nm, the TM mode and the TE mode can be coupled simultaneously, and the high coupling efficiency between the high refractive index waveguide 120 and the optical fiber can be achieved by reducing the width of the high refractive index waveguide 120.
In some embodiments, referring to FIGS. 11-14, high index waveguide 120 is silicon, low index cladding 130 is silicon dioxide, and substrate 111 of substrate 110 is silicon.
As shown in fig. 11, the low refractive index cladding 130 has a thickness of 2.6 μm, and when the thickness of the high refractive index waveguide 120 is less than 10nm, the high refractive index waveguide 120 cannot effectively confine the TE fundamental mode, and as shown in fig. 12, when the thickness of the high refractive index waveguide 120 is less than 50nm, the high refractive index waveguide 120 cannot effectively confine the TM fundamental mode. Therefore, the first predetermined value may be less than or equal to 40nm and greater than 10nm, and TE fundamental mode coupling between the first end portion 1201 of the high refractive index waveguide 120 and the optical fiber 20 can be used to implement single mode polarization.
In particular to the embodiment shown in FIGS. 11-14, the high index waveguide 120 is oriented in a second direction F 2 Is 600nm, the first end 1201 of the high index waveguide 120 has a thickness of 30nm, the coupling efficiency from the optical fiber 20 to the high index waveguide 120 can reach 95%, and the corresponding coupling loss is 0.22dB.
In other embodiments, the high refractive index waveguide 120 is made of silicon, the low refractive index cladding 130 is made of silicon dioxide, the substrate 111 of the substrate 110 is made of silicon, the first predetermined value may be greater than 40nm, the TM mode and the TE mode may be coupled simultaneously, and the coupling efficiency between the high refractive index waveguide 120 and the optical fiber may be achieved by reducing the width of the high refractive index waveguide 120.
In some embodiments, the substrate 110 includes a substrate 111 and an isolation layer 112 stacked, the high refractive index waveguide 120 is disposed on the isolation layer 112, and the low refractive index cladding 130 covers the high refractive index waveguide 120 and contacts the isolation layer 112. The low index cladding 130 is the same material as the spacer layer 112.
When the thickness of spacer layer 112 is comparable to the mode field size, the thickness of low index cladding layer 130 may be greater than or equal to the thickness of spacer layer 112. When the thickness of spacer layer 112 is greater than the mode field size, the thickness of low index cladding layer 130 may be less than the thickness of spacer layer 112 and greater than the mode field size.
In the present embodiment, the thickness of the isolation layer 112 is equivalent to the mode field size, and the thickness of the low refractive index cladding layer 130 is slightly larger than the thickness of the isolation layer 112.
It can be appreciated that the high index waveguide 120 is disposed between the low index cladding 130 and the spacer 112, which are made of the same material, so as to facilitate guiding the optical fiber 20 to be substantially transmitted to the first end portion 1201 of the high index waveguide 120 in a centered TE mode, which is beneficial to improving the coupling efficiency of the optical waveguide coupler 10.
As can be seen from fig. 7, when the thickness of the low refractive index cladding 130 is greater than 2.5 μm, the TE coupling efficiency from the optical fiber 20 to the high refractive index waveguide 120 is about 96%, and illustratively, the thickness of the low refractive index cladding 130 is 2.6 μm, and the thickness of the low refractive index cladding 130 is substantially equal to the thickness of the isolation layer 112 of the substrate 110, which is beneficial for guiding the optical fiber 20 to be approximately centrally transmitted to the first end 1201 of the high refractive index waveguide 120 in the TE mode.
In some embodiments, the second direction F of the high index waveguide 120 2 The size of the waveguide is 600nm-1400nm, namely the width of the high-refractive-index waveguide 120 is 600nm-1400nm, so that a time-consuming and high-cost electron beam exposure process can be abandoned, an ultraviolet lithography machine is selected for preparation, the preparation time and cost can be saved, the repeatability is high, the method is suitable for mass production, and a new possibility is provided for the end face coupling and packaging of the integrated lithium niobate platform on the premise of ensuring the coupling efficiency.
In some embodiments, the first portion 121 is along the first direction F 1 Is greater than or equal to 120 μm.
That is, the length of the first portion 121 is greater than or equal to 120 μm.
If the length of the first portion 121 is too short to satisfy adiabatic transmission, i.e. radiation loss is large during optical field transmission, the length of the first portion 121 is preferably greater than or equal to 120 μm.
In addition, the length of the first portion 121 is not preferably too long. If the length of the first portion 121 is too long, the process is not favorable, the integration is reduced, and the insertion loss is increased, for which reason, the first portion 121 extends along the first direction F 1 The size of (A) needs to be reasonableE.g. 200 μm, is beneficial to processing and manufacturing and can improve the total coupling efficiency.
In some embodiments, referring to FIG. 8, the high index waveguide 120 is lithium niobate, the low index cladding 130 is silica, the substrate 111 of the substrate 110 is silicon, the low index cladding 130 has a thickness of 2.6 μm, and the first portion 121 extends along a first direction F 1 Is 120 μm, it can be seen from FIG. 8 that most of the TE of the optical fiber 20 0 Is transmitted into the high index waveguide 120. The total coupling efficiency of the optical waveguide coupler 10 is 87%, and the corresponding coupling loss is 0.61dB.
In some embodiments, referring to FIG. 13, the high index waveguide 120 is silicon, the low index cladding 130 is silicon dioxide, the substrate 111 of the substrate 110 is silicon, the low index cladding 130 has a thickness of 2.6 μm, and the first portion 121 extends along a first direction F 1 Is 120 μm, it can be seen from FIG. 13 that most of the TE of the optical fiber 20 0 Is transmitted into the high index waveguide 120. The total coupling efficiency of the optical waveguide coupler 10 is 88%, corresponding to a coupling loss of 0.56dB.
In some embodiments, the first end 1201 of the high index waveguide 120 is coupled to the optical fiber 20 and the center of the first end 1201 coincides with the central axis of the core 21 of the optical fiber 20.
Specifically, in the embodiment shown in fig. 9, the high refractive index waveguide 120 is made of lithium niobate, the low refractive index cladding 130 is made of silica, and the substrate 111 of the substrate 110 is made of silicon, and it can be seen from fig. 9 that the larger the offset amount of the center of the core 21 of the optical fiber 20 from the center of the first end 1201 of the high refractive index waveguide 120, the larger the coupling loss.
Specifically, in the embodiment shown in fig. 14, the high-index waveguide 120 is made of silicon, the low-index cladding 130 is made of silicon dioxide, and the substrate 111 of the substrate 110 is made of silicon, and it can be seen from fig. 14 that the larger the offset amount of the center of the core 21 of the optical fiber 20 from the center of the first end 1201 of the high-index waveguide 120, the larger the coupling loss.
In this way, it is preferable to provide the first end portion 1201 of the high refractive index waveguide 120 in alignment with the core 21 of the optical fiber 20, which can effectively improve the coupling efficiency of the optical waveguide coupler 10.
In the embodiment shown in fig. 10, the coupling efficiency of the optical waveguide coupler 10 is higher than 50% in the wavelength range of 1 μm to 2 μm, and the corresponding coupling loss is less than 3dB, i.e. the operating bandwidth of the optical waveguide coupler 10 is greater than 1000nm.
In the embodiment shown in fig. 15, the coupling efficiency of the optical waveguide coupler 10 is higher than 65% in the wavelength range of 1.3-2 μm, and the corresponding coupling loss is less than 3dB, i.e. the operating bandwidth of the optical waveguide coupler 10 is larger than 700m.
Fig. 16 is a schematic flow chart showing a method for manufacturing an optical waveguide coupler according to an embodiment of the present application.
Referring to fig. 16 and 18, a method for manufacturing an optical waveguide coupler 10 according to an embodiment of the present disclosure includes the following steps:
s310, providing the substrate 110.
S320, forming a first direction F on the substrate 110 1 An extended high index waveguide 120.
S330, a low index cladding 130 is formed overlying the high index waveguide 120 and in contact with the substrate 110.
S340, polishing or cracking is carried out so that the thickness of the first end portion 1201 of the high refractive index waveguide 120 is a first preset value, and the first end portion 1201 of the high refractive index waveguide 120 is along the second direction F 2 Is a second predetermined value to enable TE fundamental mode coupling of the first end portion 1201 to the optical fiber 20.
Wherein the high refractive index waveguide 120 has a first direction F 1 The first end portion 1201 and the second end portion 1202 are oppositely disposed, the first end portion 1201 being closer to the optical fiber 20 than the second end portion 1202.
Step S340 of polishing or cleaving may be polishing the same end of substrate 110, high index waveguide 120, and low index cladding 130 to make the same end of substrate 110 as first end 1201 and the same end of high index waveguide 120 as first end 1201 flush with first end 1201. Of course, substrate 110, high index waveguide 120, and low index cladding 130 may be cleaved such that the end of substrate 110 facing first end 1201 is flush with the end of high index waveguide 120 facing first end 1201.
In some embodiments, referring to fig. 17 and 18, the substrate 110 includes a base 111 and an isolation layer 112 sequentially stacked, and the substrate 110 is formed along a first direction F 1 The steps of extending the high index waveguide 120 include:
s321, as shown in fig. 18a, a high refractive index waveguide layer 113 is formed on the spacer layer 112.
S322, as shown in FIG. 18b, the surface of the high refractive index waveguide layer 113 is thinned so that the thickness of the high refractive index waveguide layer 113 is in the first direction F 1 And gradually decreases upward.
S323, as shown in fig. 18c, the high refractive index waveguide layer 113 is etched to etch the high refractive index waveguide layer 113 into the high refractive index waveguide 120 having a ridge structure or a line structure.
In the present embodiment, the first direction F is formed on the substrate 110 1 After the step of extending the high index waveguide 120, the method of making the optical waveguide coupler 10 further comprises:
s330, as shown in fig. 18d, a low refractive index cladding 130 is formed overlying the high refractive index waveguide 120 and in contact with the substrate 110.
S340, as shown in fig. 18e, polishing the same end of the substrate 110, the high refractive index waveguide 120 and the low refractive index cladding 130, so that the same end of the substrate 110 as the first end portion 1201 faces, and the same end of the high refractive index waveguide 120 as the first end portion 1201 faces are flush with the first end portion 1201, and the thickness of the first end portion 1201 of the high refractive index waveguide 120 is a first preset value, and the first end portion 1201 of the high refractive index waveguide 120 is along the second direction F 2 Is a second preset value.
The preparation method of the optical waveguide coupler 10 has the advantage of simple preparation process, and since the low-refractive-index cladding 130 covers the high-refractive-index waveguide 120, the process of the low-refractive-index cladding 130 can be omitted, and only a single etching (an ultraviolet lithography machine can be selected for etching the high-refractive-index waveguide 120) needs to be performed on the high-refractive-index waveguide 120, so that the preparation steps are simplified, and the preparation cost is reduced. In addition, the polishing process used in the manufacturing process of the optical waveguide coupler 10 can greatly reduce the manufacturing cost of the optical waveguide coupler 10.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. An optical waveguide coupler for coupling to an optical fiber, the optical waveguide coupler comprising:
a substrate; and
a high refractive index waveguide formed on the substrate and extending in a first direction; the high refractive index waveguide has a first end portion and a second end portion which are oppositely arranged along a first direction; the first end is closer to the optical fiber than the second end;
a low index cladding overlying to the high index waveguide and in contact with the substrate;
the thickness of the first end part of the high-refractive-index waveguide is a first preset value, and the size of the first end part of the high-refractive-index waveguide along a second direction is a second preset value, so that the first end part can be in TE fundamental mode coupling with the optical fiber;
wherein the first direction and the second direction are perpendicular to each other.
2. The optical waveguide coupler of claim 1, wherein the first predetermined value is less than or equal to 120nm and the second predetermined value is greater than or equal to 250nm.
3. The optical waveguide coupler of claim 1, wherein an absolute difference between the refractive index of the low-index cladding and the refractive index of the core of the optical fiber is smaller than an absolute difference between the refractive index of the high-index waveguide and the refractive index of the core of the optical fiber.
4. The optical waveguide coupler of claim 1, wherein the substrate includes a base and an isolation layer arranged in a stack;
the high-refractive-index waveguide is arranged on the isolation layer;
the low-refractive-index cladding layer covers the high-refractive-index waveguide and is in contact with the isolation layer;
the low-refractive-index cladding layer and the isolation layer are made of the same material.
5. The optical waveguide coupler according to claim 1, wherein the high refractive index waveguide includes a first portion and a second portion connected in series and extending in a first direction;
the first end part is arranged at one end of the first part far away from the second part, and the second end part is arranged at one end of the second part far away from the first part;
the thickness of the first portion gradually increases from the first end to the second end along the first direction;
the thickness of the second portion remains constant along the first direction.
6. The optical waveguide coupler of claim 5, wherein a dimension of the first portion along the first direction is greater than or equal to 120 μm.
7. The optical waveguide coupler of claim 5, wherein the low index cladding comprises a third portion and a fourth portion connected in series;
the third part covers the first part and is in contact with the substrate;
the fourth portion overlies the second portion.
8. The optical waveguide coupler of claim 1, wherein the first end of the high index waveguide is directly coupled to the optical fiber and a center of the first end coincides with a central axis of a core of the optical fiber.
9. A method for manufacturing an optical waveguide coupler is characterized by comprising the following steps:
providing a substrate;
forming a high refractive index waveguide extending in a first direction on the substrate;
forming a low index cladding overlying the high index waveguide and in contact with the substrate;
polishing or cracking to make the thickness of the first end of the high-refractive-index waveguide be a first preset value, and the size of the first end of the high-refractive-index waveguide along the second direction be a second preset value, so that the first end can be coupled with the optical fiber in a TE fundamental mode; wherein the high refractive index waveguide has the first end portion and the second end portion disposed opposite to each other in a first direction;
wherein the first end is closer to the optical fiber than the second end;
the first direction and the second direction are perpendicular to each other.
10. The method for manufacturing an optical waveguide coupler according to claim 9, wherein the substrate includes a base and an isolation layer which are stacked, and the forming of the high refractive index waveguide extending in the first direction on the substrate specifically includes:
forming a high refractive index waveguide layer on the isolation layer;
thinning the surface of the high-refractive-index waveguide layer to gradually reduce the thickness of the high-refractive-index waveguide layer in the first direction;
and etching the high-refractive-index waveguide layer to etch the high-refractive-index waveguide layer into the high-refractive-index waveguide with a ridge structure or a line structure.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20050023678A (en) * | 2003-09-02 | 2005-03-10 | 한국과학기술연구원 | Ultrashort polarization- independent vertical directional coupler switch |
| US20130322813A1 (en) * | 2010-12-29 | 2013-12-05 | Socpra Sciences Et Genie S.E.C. | Low loss directional coupling between highly dissimilar optical waveguides for high refractive index integrated photonic circuits |
| WO2021178727A1 (en) * | 2020-03-04 | 2021-09-10 | The Regents Of The University Of California | Evanescent coupler mode converters |
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2022
- 2022-10-17 CN CN202211266246.4A patent/CN115933052A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20050023678A (en) * | 2003-09-02 | 2005-03-10 | 한국과학기술연구원 | Ultrashort polarization- independent vertical directional coupler switch |
| US20130322813A1 (en) * | 2010-12-29 | 2013-12-05 | Socpra Sciences Et Genie S.E.C. | Low loss directional coupling between highly dissimilar optical waveguides for high refractive index integrated photonic circuits |
| WO2021178727A1 (en) * | 2020-03-04 | 2021-09-10 | The Regents Of The University Of California | Evanescent coupler mode converters |
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