Low-crosstalk optical waveguide and refractive index detection device and method
By using anisotropic base layer composed of a variety of dielectric materials in the optical waveguide, the electric field distribution of the waveguide symmetric mode and anti-symmetric mode is changed, the problems of large size and complex design of the optical waveguide structure in the prior art are solved, and high integration is achieved and miniaturized optical systems.
Patent Information
- Application Number
- CN202411662028.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-20
- Publication Date
- 2025-02-07
AI Technical Summary
In the prior art, by increasing the distance between optical waveguides to suppress crosstalk, the optical waveguide structure is large, affecting the miniaturization of the optical chip; while suppressing crosstalk with different sizes can reduce the volume of the optical waveguide, but The design process is complex, the design efficiency is inefficient and the bandwidth to suppress crosstalk is narrow.
An anisotropic base layer composed of a variety of dielectric materials is formed by arranging a plurality of substrate units on a horizontal plane to form an equivalent anisotropic base layer, and a waveguide core layer is provided on its surface. This structure can change the electric field distribution of the waveguide symmetric mode and the anti-symmetric mode, so that its effective refractive index difference is approaching 0, reducing crosstalk between the waveguides.
It realizes that crosstalk between adjacent waveguides is effectively suppressed without increasing the volume of the optical waveguide, and the integration and miniaturization of the optical system are improved. At the same time, the design is simple and the bandwidth to suppress crosstalk is wide.
Smart Images
Figure CN119395813A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of optical signal transmission, and in particular to a low crosstalk optical waveguide, a refractive index detection device and a method. Background Art
[0002] With the development of modern optical technology, optical chips with various functions have emerged, such as optical computing chips and optical chips for biological detection. As an important component in optical chips, the performance and integration of optical waveguides directly affect the performance and miniaturization of optical chips.
[0003] 1550nm wavelength is a commonly used communication wavelength for optical transmission. The optical waveguide structure used is usually silicon as the core layer, silicon dioxide as the substrate, and vacuum as the cover layer. When the spacing between waveguides in the silicon core layer is small, the crosstalk between adjacent waveguides increases significantly, resulting in a decrease in the performance of the optical chip. Therefore, the optical waveguide of this structure needs to increase the spacing between adjacent waveguides to suppress the crosstalk between waveguides, which leads to a large volume of the optical waveguide, and then leads to a small integration of the optical chip, which is not conducive to the miniaturization of the optical system. Another optical waveguide structure is to arrange several waveguides of different widths and heights together to form a waveguide superlattice. Since waveguides of different sizes support different propagation modes, the direct coupling between waveguides is reduced, and the crosstalk between adjacent waveguides can be suppressed without increasing the spacing between adjacent waveguides. Although this design can reduce the size of the optical waveguide to a certain extent and improve the integration of the optical chip, its effect of suppressing crosstalk is too dependent on the width and height of each waveguide, and the size of each waveguide needs to be accurately calculated, resulting in a relatively complex design process, low design efficiency, and can only suppress crosstalk in a narrow broadband range.
[0004] In summary, increasing the distance between adjacent waveguides to suppress crosstalk between adjacent waveguides will result in a larger volume of the optical waveguide structure, which will affect the miniaturization of the optical chip; using waveguides of different sizes to suppress crosstalk between adjacent waveguides can reduce the volume of the optical waveguide and improve the integration of the optical chip, but its design process is relatively complicated, the design efficiency is low, and its bandwidth for suppressing crosstalk is narrow. Summary of the invention
[0005] To this end, the technical problem to be solved by the present invention is to overcome the problem in the prior art that increasing the distance between adjacent waveguides to suppress crosstalk between adjacent waveguides will result in a larger volume of the optical waveguide structure, thereby affecting the miniaturization of the optical chip; using waveguides of different sizes to suppress crosstalk between adjacent waveguides can reduce the volume of the optical waveguide and improve the integration of the optical chip, but its design process is relatively complicated, the design efficiency is low, and the bandwidth for suppressing crosstalk is narrow.
[0006] In order to solve the above technical problems, the present invention provides a low crosstalk optical waveguide, comprising: An anisotropic substrate layer, comprising a plurality of substrate units arranged in a horizontal plane, each of the substrate units comprising a plurality of substrates arranged in a horizontal plane; A waveguide core layer is arranged on the surface of the anisotropic base layer; Among them, the materials of each substrate in each substrate unit are different dielectric materials; when the propagation mode of the electromagnetic wave is the TE mode, the multiple substrate units and the multiple substrates in each substrate unit are arranged in a direction perpendicular to the propagation direction of the electromagnetic wave; when the propagation mode of the electromagnetic wave is the TM mode, the multiple substrate units and the multiple substrates in each substrate unit are arranged along the propagation direction of the electromagnetic wave.
[0007] Preferably, the silicon dioxide substrate layer is continuously disposed on the surface of the anisotropic substrate layer away from the waveguide core layer.
[0008] Preferably, the distance between two adjacent substrate units is 0; and / or The distance between two adjacent substrates in each substrate unit is 0; and / or The height of the substrate unit is 50nm~500nm; and / or The width of the substrate unit is less than 0.13 times of the vacuum wavelength.
[0009] Preferably, when the propagation mode of the electromagnetic wave is the TE mode, the width of each of the substrate units is smaller than the width of each waveguide in the waveguide core layer, and the length of each of the substrate units is greater than or equal to the length of each waveguide in the waveguide core layer; When the propagation mode of the electromagnetic wave is the TM mode, the sum of the widths of all the substrate units is greater than or equal to the length of each waveguide in the waveguide core layer.
[0010] Preferably, when the propagation mode of the electromagnetic wave is TE0 mode, The width of each waveguide in the waveguide core layer is 440 nm, the height of each waveguide is 220 nm, and the distance between two adjacent waveguides is 400 nm; Each of the substrate units includes a first substrate and a second substrate; The distance between two adjacent substrate units and the distance between the first substrate and the second substrate are both 0; The width of the substrate unit is 120 nm, the width of the first substrate is 80 nm, the width of the second substrate is 40 nm, and the height of the first substrate and the height of the second substrate are both 380 nm.
[0011] Preferably, when the propagation mode of the electromagnetic wave is TM0 mode, The width of each waveguide in the waveguide core layer is 450 nm, the height of each waveguide is 220 nm, and the distance between two adjacent waveguides is 450 nm; Each of the substrate units includes a first substrate and a second substrate; The distance between two adjacent substrate units and the distance between the first substrate and the second substrate are both 0; The width of the first substrate is 100 nm, the width of the second substrate is 100 nm, and the height of the first substrate and the height of the second substrate are both 94 nm.
[0012] Preferably, when the propagation mode of the electromagnetic wave is TE1 mode, The width of each waveguide in the waveguide core layer is 800 nm, the height of each waveguide is 220 nm, and the distance between two adjacent waveguides is 400 nm; Each of the substrate units includes a first substrate and a second substrate; The distance between two adjacent substrate units and the distance between the first substrate and the second substrate are both 0; The width of the first substrate is 80 nm, the width of the second substrate is 40 nm, and the height of the first substrate and the height of the second substrate are both 350 nm.
[0013] Preferably, the dielectric material includes silicon, silicon dioxide, silicon nitride, aluminum nitride, or titanium dioxide.
[0014] The present invention also provides a refractive index detection device, comprising: The low crosstalk optical waveguide as described above; A crosstalk detection device is connected to the low-crosstalk optical waveguide, and is used to detect a first crosstalk value curve of the low-crosstalk optical waveguide within a preset working wavelength range; and after the medium to be detected is filled between adjacent waveguides of the waveguide core layer in the low-crosstalk optical waveguide and on the surface of the waveguide core layer away from the anisotropic substrate layer, a second crosstalk value curve of the low-crosstalk optical waveguide within the preset working wavelength range is detected; A host computer, which is in communication connection with the crosstalk detection device, is used to obtain a first operating wavelength corresponding to the minimum value in the first crosstalk value curve, and a second operating wavelength corresponding to the minimum value in the second crosstalk value curve, and calculate the refractive index of the medium to be detected based on the first operating wavelength, the second operating wavelength and the vacuum refractive index; Wherein, the calculation formula of the refractive index of the medium to be detected is: , in, Indicates the refractive index of the medium to be detected; represents the second operating wavelength; represents the first operating wavelength; Represents the refractive index of vacuum.
[0015] The present invention also provides a refractive index detection method, which is applied to the above-mentioned refractive index detection device, comprising: Detecting a first crosstalk value curve of the low crosstalk optical waveguide within a preset operating wavelength range, and obtaining a first operating wavelength corresponding to a minimum value in the first crosstalk value curve; Filling a medium to be detected between adjacent waveguides of the waveguide core layer in the low crosstalk optical waveguide and on the surface of the waveguide core layer away from the anisotropic substrate layer; Detecting a second crosstalk value curve of the low crosstalk optical waveguide after being filled with the medium to be detected within a preset working wavelength range, and obtaining a second working wavelength corresponding to a minimum value in the second crosstalk value curve; The refractive index of the medium to be detected is calculated based on the first working wavelength, the second working wavelength and the vacuum refractive index.
[0016] The low crosstalk optical waveguide provided by the present application utilizes substrates of multiple dielectric materials arranged on a horizontal plane to obtain substrate units. According to the equivalent medium theory, multiple substrate units are arranged on a horizontal plane to obtain an anisotropic substrate layer equivalent to an anisotropic material. The waveguide core layer is arranged on the surface of the anisotropic substrate layer. Since the anisotropic substrate unit can change the electric field distribution of the symmetric mode and the antisymmetric mode of the waveguide, the effective refractive index difference between the symmetric mode and the antisymmetric mode of the waveguide is changed, so that the effective refractive index difference between the symmetric mode and the antisymmetric mode of the waveguide approaches 0, and then the coupling length of the waveguide approaches infinity, and the crosstalk between adjacent waveguides is almost 0, which can effectively reduce the crosstalk between waveguides even when the distance between adjacent waveguides is small. The invention discloses a low-crosstalk optical waveguide with a simple design, which can suppress the crosstalk between adjacent waveguides in a broadband range of 1300nm to 1634nm for the TE0 mode. In addition, the crosstalk between adjacent waveguides can be suppressed in the TE mode and the TM mode respectively by changing the arrangement direction of the substrate unit and the substrates in the substrate unit. At the same time, since the anisotropic substrate layer is obtained by using a dielectric material with extremely low loss, the electromagnetic wave can be transmitted with low loss in the optical waveguide. The low-crosstalk optical waveguide provided by the present application is simple in design, and can effectively suppress the crosstalk between adjacent waveguides in a wider broadband range while reducing the volume of the optical waveguide, thereby improving the integration of the optical chip and the miniaturization of the optical system. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein: Figure 1Schematic diagram of the low crosstalk optical waveguide structure in TE mode provided in this application; Figure 2 Schematic diagram of the low crosstalk optical waveguide structure in the TM mode provided by this application; Figure 3 A schematic diagram of a low crosstalk optical waveguide and its related parameters when the waveguide core layer includes two waveguides provided in the present application; wherein, Figure 3 (a) is a schematic diagram of the cross section of the low crosstalk optical waveguide and the electric field distribution of the symmetric mode and the antisymmetric mode. Figure 3 (b) is a schematic diagram showing the distribution of the absolute value of the difference between the effective refractive index of the symmetric mode and the antisymmetric mode with respect to the thickness of the substrate unit and the operating wavelength. Figure 3 (c) is a graph showing the absolute value of the difference between the effective refractive index of the symmetric mode and the antisymmetric mode as a function of the operating wavelength. Figure 3 (d) is a schematic diagram showing the comparison of the normalized coupling length of the low crosstalk optical waveguide and the traditional optical waveguide as a function of the operating wavelength; Figure 4 Schematic diagram of the performance comparison between low crosstalk optical waveguide and traditional optical waveguide under TE fundamental mode; Figure 4 (a) is a schematic diagram of the crosstalk curve of the two optical waveguides changing with the working wavelength. Figure 4 (b) is a schematic diagram of the electric field mode distribution of the two optical waveguides at different wavelengths; Figure 5 A schematic diagram of a curve showing a change in crosstalk of a low crosstalk optical waveguide with operating wavelength when the waveguide core layer is in TM fundamental mode (i.e., TM0 mode) and contains two waveguides; Figure 6 Schematic diagram of the curve of the transmission rate of the TE fundamental mode changing with the working wavelength when it propagates in a low crosstalk optical waveguide at different bending angles; Figure 6 (a) is a schematic diagram of the curve of the transmittance of the TE fundamental mode when propagating in a low crosstalk optical waveguide with a bending angle of 90° versus the operating wavelength. Figure 6 (b) is a schematic diagram of the curve of the transmittance of the TE fundamental mode changing with the working wavelength when propagating in a low crosstalk optical waveguide with a bending angle of 180°; Figure 7 Schematic diagram of low crosstalk optical waveguide and its related parameters when the waveguide core layer contains seven waveguides in the TE fundamental mode; wherein, Figure 7 (a) is a schematic diagram of the cross section of a low crosstalk optical waveguide. Figure 7 (b) shows the TE fundamental mode in Figure 7 Schematic diagram comparing the curve of the transmittance of the structure shown in (a) with that of the traditional silicon dioxide-based optical waveguide when propagating with the operating wavelength; Figure 8A schematic diagram of the low crosstalk optical waveguide and its related parameters in the TE1 mode provided in this application; wherein: Figure 8 (a) is a schematic diagram of the electric field distribution of the symmetric mode of the low crosstalk optical waveguide in the TE1 mode. Figure 8 (b) is a schematic diagram of the electric field distribution of the antisymmetric mode of the low crosstalk optical waveguide in the TE1 mode. Figure 8 (c) is a schematic diagram showing the comparison of the normalized coupling length of the low crosstalk optical waveguide and the traditional optical waveguide under the TE1 mode with the change of the working wavelength. Figure 8 (d) is a schematic diagram comparing the crosstalk curves of the low crosstalk optical waveguide and the traditional optical waveguide in the TE1 mode with the change of the working wavelength; Fig. 9 A schematic diagram of a structure in which a medium to be detected is arranged on a low crosstalk optical waveguide; Fig.10 Schematic diagram of the principle of low crosstalk optical waveguide for detecting refractive index; Fig.10 (a) is a schematic diagram of the crosstalk curve of the low crosstalk optical waveguide as the refractive index of the medium to be detected changes with the working wavelength. Fig.10 (b) is a schematic diagram of a curve showing a change in the refractive index of the medium to be detected and the working wavelength corresponding to the lowest crosstalk value of the low crosstalk optical waveguide; Explanation of the reference numerals in the specification: 1. anisotropic substrate layer; 11. substrate unit; 111. first substrate; 112. second substrate; 2. waveguide core layer; 21. waveguide; 3. silicon dioxide substrate layer; 4. medium to be detected. DETAILED DESCRIPTION
[0018] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.
[0019] Coupling length It refers to the propagation distance required for energy to be completely transferred from one waveguide to an adjacent waveguide. Therefore, the crosstalk between adjacent waveguides can be determined by the coupling length. The calculation formula is: , in, The operating wavelength of the optical waveguide; represents the effective refractive index of the symmetric mode of the waveguide; represents the effective refractive index of the antisymmetric mode of the waveguide.
[0020] From the above formula, it can be seen that when When the coupling length will approach infinity, which means that the crosstalk between adjacent waveguides is almost zero. and When the absolute value of the difference approaches to 0, the crosstalk between adjacent waveguides also approaches 0. Therefore, the crosstalk between adjacent waveguides can be reduced by changing the difference in the effective refractive index of the symmetric mode and the antisymmetric mode of the waveguide.
[0021] Based on the above principle, this application provides a low crosstalk optical waveguide. Figure 1 and Figure 2 The low crosstalk optical waveguide specifically includes an anisotropic substrate layer 1 and a waveguide core layer 2.
[0022] The anisotropic substrate layer 1 includes a plurality of substrate units 11 arranged on a horizontal plane, and each substrate unit 11 includes a plurality of substrates arranged on a horizontal plane.
[0023] The waveguide core layer 2 is arranged on the surface of the anisotropic base layer 1 .
[0024] Specifically, the waveguide core layer 2 includes a plurality of waveguides 21 ; in one embodiment, the waveguide core layer 2 may be a silicon core layer, that is, the material of each waveguide 21 in the waveguide core layer 2 is silicon.
[0025] Specifically, the materials of the substrates in each substrate unit 11 are different dielectric materials.
[0026] When the propagation mode of the electromagnetic wave is the TE mode, the multiple substrate units 11 and the multiple substrates in each substrate unit 11 are arranged along a direction perpendicular to the propagation direction of the electromagnetic wave; when the propagation mode of the electromagnetic wave is the TM mode, the multiple substrate units 11 and the multiple substrates in each substrate unit 11 are arranged along the propagation direction of the electromagnetic wave.
[0027] Furthermore, the dielectric material includes silicon, silicon dioxide, silicon nitride, aluminum nitride, titanium dioxide, and the like.
[0028] In one embodiment, each substrate unit 11 includes a first substrate 111 and a second substrate 112 of different materials, the first substrate 111 is made of silicon, and the second substrate 112 is made of silicon dioxide. In other embodiments of the present application, each substrate unit 11 may also include 3, 4, 5 or more substrates.
[0029] like Figure 1 As shown in , when the propagation mode of the electromagnetic wave is the TE mode, the electromagnetic wave propagates along the z-axis direction, the multiple substrate units 11 are arranged along the x-axis direction, and the first substrate 111 and the second substrate 112 in each substrate unit 11 are also arranged along the x-axis direction; like Figure 2As shown in , when the propagation mode of the electromagnetic wave is the TM mode, the electromagnetic wave propagates along the z-axis direction, multiple substrate units 11 are arranged along the z-axis direction, and the first substrate 111 and the second substrate 112 in each substrate unit 11 are also arranged along the z-axis direction.
[0030] The present application arranges substrates of various dielectric materials on a horizontal plane to obtain substrate units. According to the equivalent medium theory, multiple substrate units are arranged on a horizontal plane to obtain an anisotropic substrate layer equivalent to an anisotropic material. The waveguide core layer is disposed on the surface of the anisotropic substrate layer. The anisotropic substrate layer is used to change the electric field distribution of the symmetric mode and the antisymmetric mode of the waveguide, thereby changing the effective refractive index difference between the symmetric mode and the antisymmetric mode of the waveguide, so that the effective refractive index difference between the symmetric mode and the antisymmetric mode of the waveguide is close to 0, thereby making the coupling length of the waveguide approach infinity, and the crosstalk between adjacent waveguides It is almost 0, and the crosstalk between waveguides can be effectively reduced even when the distance between adjacent waveguides is small, thereby improving the integration of the optical system. The design is simple, and the crosstalk between adjacent waveguides can be suppressed in the broadband range of 1300nm~1634nm for the TE0 mode; in addition, by changing the arrangement direction of the substrate unit and each substrate in the substrate unit, the crosstalk between adjacent waveguides can be suppressed in the TE mode and TM mode respectively. At the same time, since the anisotropic substrate layer is obtained by using extremely low-loss dielectric materials, electromagnetic waves can be transmitted with low loss in the optical waveguide.
[0031] Further, in some embodiments of the present application, Figure 1 or Figure 2 As shown, the low crosstalk optical waveguide further includes a silicon dioxide base layer 3 .
[0032] The silicon dioxide base layer 3 is continuously arranged on the surface of the anisotropic base layer 1 on the side away from the waveguide core layer 2 .
[0033] Using the silicon dioxide substrate layer 3 to support the anisotropic substrate layer 1 can make the anisotropic substrate layer 1 more stable, further reduce the difference between the effective refractive index of the symmetric mode and the effective refractive index of the antisymmetric mode, and thus further reduce the crosstalk between the waveguides 21 .
[0034] Further, the distance between two adjacent substrate units 11 is 0; and / or the distance between two adjacent substrates in each substrate unit 11 is 0.
[0035] Further, the height of the substrate unit 11 is 50nm~500nm, for example: 50nm, 73nm, 96nm, 119nm, 142nm, 165nm, 188nm, 211nm, 234nm, 257nm, 280nm, 303nm, 326nm, 349nm, 377nm, 400nm, 423nm, 446nm, 469nm or 500nm; and / or, the width of the substrate unit 11 is less than 0.13 times the vacuum wavelength, for example: 0.03, 0.05, 0.07, 0.09 or 0.11.
[0036] By limiting the substrate unit 11 and the substrate spacing and size as described above, the anisotropic substrate layer 1 can better suppress the crosstalk between adjacent waveguides 21, thereby improving the performance of the low-crosstalk optical waveguide.
[0037] Further, when the propagation mode of the electromagnetic wave is the TE mode, the width of the substrate unit 11 is smaller than the width of each waveguide 21 in the waveguide core layer 2, and the length of the substrate unit 11 is greater than or equal to the length of each waveguide 21 in the waveguide core layer 2. When the propagation mode of the electromagnetic wave is the TM mode, the sum of the widths of all substrate units 11 is greater than or equal to the length of each waveguide 21 in the waveguide core layer 2.
[0038] In this application, the length of the substrate unit 11 and the substrate refers to the length of the sides of the substrate unit 11 and the substrate parallel to the direction of electromagnetic wave propagation; the width of the substrate unit 11 and the substrate refers to the length of the sides of the substrate unit 11 and the substrate perpendicular to the direction of electromagnetic wave propagation.
[0039] When the propagation mode of the electromagnetic wave is the TE mode, since the setting direction of each substrate unit 11 is the same as that of the waveguide 21, by limiting the width of each substrate unit 11 to be smaller than the width of the waveguide 21 and limiting the length of each substrate unit 11 to be greater than or equal to the length of the waveguide 21, one or more substrate units 11 can be arranged under each waveguide 21, so that the effective refractive index of the symmetric mode and the antisymmetric mode of the optical waveguide can be better adjusted, and the crosstalk between adjacent waveguides 21 can be suppressed.
[0040] When the propagation mode of the electromagnetic wave is the TM mode, since the setting direction of each substrate unit 11 is perpendicular to the waveguide 21, by limiting the sum of the widths of all substrate units 11 to be greater than or equal to the length of the waveguide 21, the substrate unit 11 can be set under the entire waveguide 21, thereby suppressing crosstalk between adjacent waveguides 21.
[0041] In one embodiment, when the propagation mode of the electromagnetic wave is the TE0 mode, The width of each waveguide 21 in the waveguide core layer 2 is 440 nm, the height of each waveguide 21 is 220 nm, and the distance between two adjacent waveguides 21 is 400 nm; Each substrate unit 11 includes a first substrate 111 and a second substrate 112; The distance between two adjacent substrate units 11 and the distance between the adjacent first substrate 111 and the second substrate 112 are both 0; The width of the substrate unit 11 is 120 nm, the width of the first substrate 111 is 80 nm, the width of the second substrate 112 is 40 nm, and the height of the first substrate 111 and the height of the second substrate 112 are both 380 nm.
[0042] like Figure 3 (a) shows a schematic diagram of the cross section of a low crosstalk optical waveguide and the electric field distribution of a symmetric mode and an antisymmetric mode when the waveguide core layer includes two waveguides provided in an embodiment of the present application, and its specific dimensions are as follows: Width of waveguide 21 is 440nm, the height of the waveguide 21 is 220nm, and the distance between two adjacent waveguides 21 is 400nm; Each substrate unit 11 includes a first substrate 111 and a second substrate 112; The distance between two adjacent substrate units 11 and the distance between the adjacent first substrate 111 and the second substrate 112 are both 0; The width of the substrate unit 11 is 120 nm, and the width of the first substrate 111 is is 80 nm, and the width of the second substrate 112 is is 40 nm, and the height of the first substrate 111 and the height of the second substrate 112 (ie, the height of the substrate unit 11 ) are all 380nm.
[0043] Figure 3 (b) is a schematic diagram showing the distribution of the absolute value of the difference between the effective refractive index of the symmetric mode and the antisymmetric mode with respect to the thickness of the substrate unit and the operating wavelength. The curve in the figure indicates that the effective refractive index of the symmetric mode is equal to the effective refractive index of the antisymmetric mode. It can be seen that when the height of the substrate unit is When the optical waveguide is used as the optical waveguide for optical transmission, the effective refractive index of the symmetric mode is always equal to the effective refractive index of the antisymmetric mode at two working wavelengths, and the effective refractive index of the symmetric mode is very close to the effective refractive index of the antisymmetric mode near these two working wavelengths, which indicates that the low crosstalk optical waveguide provided by the present application can achieve a larger coupling length (i.e., smaller crosstalk) in a wider broadband range.
[0044] Figure 3 (c) in Figure 3(a) shows a curve diagram of the absolute value of the difference between the effective refractive index of the symmetric mode and the antisymmetric mode of the low crosstalk optical waveguide as a function of the operating wavelength. The points marked with a five-pointed star in the figure indicate that the effective refractive index of the symmetric mode is equal to the effective refractive index of the antisymmetric mode. The operating wavelengths corresponding to the two points are 1358nm and 1530nm, respectively. Figure 3 (d) in Figure 3 FIG. 1 is a schematic diagram showing a curve comparison of the normalized coupling length of the low crosstalk optical waveguide and the conventional optical waveguide as a function of the operating wavelength. It can be seen from the figure that the low crosstalk optical waveguide with an anisotropic substrate layer provided in this embodiment can achieve a normalized coupling length in a wide band range of 1300 nm to 1556 nm. , achieving normalized coupling length in the broadband range of 1300nm~1634nm , which fully proves that the present application can effectively suppress the crosstalk between adjacent waveguides by adding an anisotropic substrate layer, and the crosstalk suppression performance of the obtained low-crosstalk optical waveguide is far superior to that of the traditional silica-based optical waveguide.
[0045] like Figure 4 The figure shows the performance comparison between the low crosstalk optical waveguide and the traditional optical waveguide under the TE fundamental mode. The length of the waveguide in the low crosstalk optical waveguide is 100 μm, and the other dimensions are the same as Figure 3 The optical waveguide structures shown in (a) have the same dimensions; the calculation formula for the crosstalk value between adjacent waveguides is: , in, Indicates the crosstalk value between adjacent waveguides; represents the initial incident power; represents the output power coupled into the adjacent waveguide.
[0046] like Figure 4 (a) is a schematic diagram of the crosstalk curve of the two optical waveguides versus the operating wavelength. It can be seen from the figure that the crosstalk of the low crosstalk optical waveguide provided by the present application is lower than -20dB in the broadband range of 1300nm~1637nm, and its crosstalk suppression performance is much higher than that of the traditional silica-based optical waveguide.
[0047] like Figure 4 (b) is a schematic diagram of the electric field mode distribution of the two optical waveguides at different wavelengths. It can be seen from the figure that at the operating wavelengths of 1550nm and 1360nm, there is almost no energy coupling to the adjacent waveguide in the low crosstalk optical waveguide provided by the present application, while there is significant energy coupling in the traditional silica-based optical waveguide, which fully demonstrates the crosstalk suppression performance of the low crosstalk optical waveguide provided by the present application.
[0048] In one embodiment, when the propagation mode of the electromagnetic wave is the TM0 mode, The width of each waveguide 21 in the waveguide core layer 2 is 450 nm, the height of each waveguide 21 is 220 nm, and the distance between two adjacent waveguides 21 is 450 nm; Each substrate unit 11 includes a first substrate 111 and a second substrate 112; The distance between two adjacent substrate units 11 and the distance between the adjacent first substrate 111 and the second substrate 112 are both 0; The width of the first substrate 111 is 100 nm, the width of the second substrate 112 is 100 nm, and the height of the first substrate 111 and the height of the second substrate 112 are both 94 nm.
[0049] Based on the size limitation of the low crosstalk optical waveguide in the TM0 mode, a specific embodiment of the present application further provides a low crosstalk optical waveguide in a TM fundamental mode and when the waveguide core layer includes two waveguides, and its specific size is as follows: The width of each waveguide 21 is 450 nm, the height of each waveguide 21 is 220 nm, and the distance between two waveguides 21 is 450 nm; Each substrate unit 11 includes a first substrate 111 and a second substrate 112; The distance between two adjacent substrate units 11 and the distance between the adjacent first substrate 111 and the second substrate 112 are both 0; The width of the first substrate 111 is 100 nm, the width of the second substrate 112 is 100 nm, and the height of the first substrate 111 and the height of the second substrate 112 are both 94 nm.
[0050] like Figure 5 The figure shows a schematic diagram of a curve of the crosstalk of the low crosstalk optical waveguide provided in the above specific embodiment varying with the working wavelength. It can be seen from the figure that the crosstalk of the low crosstalk optical waveguide in the broadband range of 1535nm~1560nm is lower than -17.5dB, indicating that the low crosstalk optical waveguide designed in the present application can effectively suppress the crosstalk of the TM fundamental mode.
[0051] Furthermore, in order to verify that the anisotropic substrate layer 1 also has the effect of suppressing crosstalk between waveguides for the curved waveguide system, the present embodiment arranges the anisotropic substrate layer 1 in the optical waveguides with different bending angles, thereby obtaining low crosstalk optical waveguides with different bending angles. Taking the TE mode as an example, Figure 6 The figure shows the curve of the transmission rate of the TE fundamental mode when it propagates in the low crosstalk optical waveguide at different bending angles as a function of the working wavelength; Figure 6 (a) is a schematic diagram of the curve of the transmittance of the TE fundamental mode when propagating in a low crosstalk optical waveguide with a bending angle of 90° versus the operating wavelength. Figure 6(b) is a schematic diagram of the curve showing the variation of transmittance of the TE fundamental mode with the operating wavelength when propagating in a low crosstalk optical waveguide with a bending angle of 180°.
[0052] from Figure 6 It can be seen that when the turning radius of the low crosstalk optical waveguide with a bending angle of 90° is 3μm, 4μm, and 5μm, the TE fundamental mode can show high transmittance (≥95%) in the wide band range of 1300nm~1613nm; when the turning radius of the low crosstalk optical waveguide with a bending angle of 180° is 3μm, 4μm, and 5μm, the TE fundamental mode can also show high transmittance in a wider broadband range. In addition, from the magnetic field of the TE fundamental mode propagating in the low crosstalk optical waveguide with bending angles of 90° and 180° at an operating wavelength of 1550nm It can be seen from the distribution diagram that the energy is always confined to the initial excitation waveguide for transmission, and almost no energy is coupled to the adjacent waveguide.
[0053] Furthermore, this embodiment also applies the anisotropic substrate layer 1 to the waveguide array system, also taking the TE mode as an example, such as Figure 7 As shown in (a), when the propagation mode of the electromagnetic wave is the TE fundamental mode and the waveguide core layer 2 includes seven waveguides 21, The width of each waveguide 21 is 440 nm, the height of each waveguide 21 is 220 nm, and the distance between two adjacent waveguides 21 is 400 nm; Each substrate unit 11 includes a first substrate 111 and a second substrate 112; The distance between two adjacent substrate units 11 and the distance between the adjacent first substrate 111 and the second substrate 112 are both 0; The width of the first substrate 111 is 80 nm, the width of the second substrate 112 is 40 nm, and the height of the first substrate 111 and the height of the second substrate 112 are both 380 nm.
[0054] Figure 7 (b) shows the TE fundamental mode in Figure 7 The schematic diagram of the comparison of the transmittance variation curve of the structure shown in (a) and the traditional silica substrate optical waveguide when propagating in the operating wavelength is shown. It can be seen from the figure that within the broadband range of 1300nm~1587nm, the transmittance of the TE fundamental mode in the low crosstalk optical waveguide provided in this embodiment is greater than 95%, indicating that a low crosstalk optical waveguide can also be obtained by setting an anisotropic substrate layer 1 in the waveguide array system.
[0055] In addition, the anisotropic substrate layer 1 can not only suppress the crosstalk of the TE / TM fundamental mode, but also suppress the crosstalk in the high-order waveguide mode.
[0056] Specifically, in one embodiment, when the propagation mode of the electromagnetic wave is the TE1 mode, The width of each waveguide 21 in the waveguide core layer 2 is 800 nm, the height of each waveguide 21 is 220 nm, and the distance between two adjacent waveguides 21 is 400 nm; Each substrate unit 11 includes a first substrate 111 and a second substrate 112; The distance between two adjacent substrate units 11 and the distance between the adjacent first substrate 111 and the second substrate 112 are both 0; The width of the first substrate 111 is 80 nm, the width of the second substrate 112 is 40 nm, and the height of the first substrate 111 and the height of the second substrate 112 are both 350 nm.
[0057] like Figure 8 A schematic diagram of a low crosstalk optical waveguide and its related parameters in the TE1 mode provided in an embodiment of the present application; wherein: Figure 8 (a) is a schematic diagram of the electric field distribution of the symmetric mode of the low crosstalk optical waveguide in the TE1 mode. Figure 8 (b) is a schematic diagram of the electric field distribution of the antisymmetric mode of the low crosstalk optical waveguide in the TE1 mode. Figure 8 (c) is a schematic diagram showing the comparison of the normalized coupling length of the low crosstalk optical waveguide and the traditional optical waveguide under the TE1 mode with the change of the working wavelength. Figure 8 (d) is a schematic diagram comparing the crosstalk curves of the low crosstalk optical waveguide and the traditional optical waveguide in the TE1 mode with the operating wavelength.
[0058] from Figure 8 It can be seen that the coupling length of the TE high-order waveguide mode propagating in the low-crosstalk optical waveguide provided by the present application is much longer than that of the traditional silica-based optical waveguide, and the crosstalk of the TE high-order waveguide mode when propagating in the low-crosstalk optical waveguide provided by the present application is much smaller than that of the traditional silica-based optical waveguide, indicating that the ability of the low-crosstalk optical waveguide provided by the present application to suppress the crosstalk of the high-order waveguide mode is much better than that of the silica-based optical waveguide.
[0059] It is worth noting that for other TE high-order waveguide modes and TM high-order waveguide modes, the effect of maximizing the suppression of crosstalk between waveguides can be achieved by changing the sizes of the waveguide, the first substrate, the second substrate and the substrate unit.
[0060] In summary, the present invention uses anisotropic materials composed of multilayer dielectric structures as optical waveguide substrates to greatly reduce the crosstalk of optical waveguides, and is applicable to dual waveguides, curved waveguides, and waveguide array systems, and is applicable not only to waveguide fundamental modes, but also to high-order waveguide modes. In addition, by adjusting the arrangement direction of the dielectric multilayer structure, the crosstalk of waveguide modes (TE mode or TM mode) with different polarizations can be effectively suppressed, and the crosstalk can be effectively suppressed within a larger bandwidth range.
[0061] Based on the low crosstalk optical waveguide provided in the above embodiment, the embodiment of the present application further provides a refractive index detection device. Since the space between adjacent waveguides 21 in the waveguide core layer 2 of the low crosstalk optical waveguide and the side of the waveguide core layer 2 away from the anisotropic substrate layer 1 are both vacuum, the refractive index is 1. Therefore, Fig. 9 As shown, when performing refractive index detection, the refractive index change of the filling medium between adjacent waveguides 21 of the waveguide core layer 2 of the medium 4 to be detected and on the surface of the waveguide core layer 2 on the side away from the anisotropic substrate layer 1 will cause the working wavelength corresponding to the minimum crosstalk value of the low crosstalk waveguide to shift. The refractive index of the medium to be detected can be calculated based on the relationship between the shift of the working wavelength corresponding to the minimum crosstalk value before and after filling the medium to be detected and the refractive index of the vacuum.
[0062] The embodiment of the present application obtains a schematic diagram of a curve of the crosstalk of a low crosstalk waveguide changing with the working wavelength when different refractive index media are located between adjacent waveguides and on the surface of the waveguide core layer through simulation, as shown in FIG. Fig.10 As shown in (a), each substrate unit in the low crosstalk optical waveguide used in the simulation includes a first substrate and a second substrate, the material of the first substrate is silicon, the material of the second substrate is silicon dioxide, the refractive index of silicon is set to 3.476, and the refractive index of silicon dioxide is set to 1.444. Fig.10 As can be seen from (a) in the figure, when the refractive index of the medium changes slightly, the operating wavelength corresponding to the lowest crosstalk value of the low crosstalk optical waveguide also shifts. Therefore, by measuring the operating wavelength corresponding to the lowest crosstalk, the refractive index of the corresponding medium to be detected can be obtained, such as Fig.10 (b) shows the working wavelength corresponding to the minimum crosstalk value under different refractive index media. When the refractive index of the medium to be detected shifts by 0.01, the working wavelength corresponding to the minimum crosstalk value shifts by about 1nm. This device for measuring refractive index using crosstalk of a low-crosstalk optical waveguide has good measurement accuracy.
[0063] Specifically, based on the above detection principle, the refractive index detection device specifically includes: The low crosstalk optical waveguide as described above; A crosstalk detection device is connected to the low-crosstalk optical waveguide, and is used to detect a first crosstalk value curve of the low-crosstalk optical waveguide within a preset working wavelength range; and after the medium to be detected is filled between adjacent waveguides of the waveguide core layer in the low-crosstalk optical waveguide and on the surface of the waveguide core layer away from the anisotropic substrate layer, a second crosstalk value curve of the low-crosstalk optical waveguide within the preset working wavelength range is detected; A host computer is connected to the crosstalk detection device for obtaining a first working wavelength corresponding to a minimum value in a first crosstalk value curve and a second working wavelength corresponding to a minimum value in a second crosstalk value curve, and calculating a refractive index of a medium to be detected based on the first working wavelength, the second working wavelength and a vacuum refractive index; Among them, the calculation formula of the refractive index of the medium to be detected is: , in, Indicates the refractive index of the medium to be detected; represents the second operating wavelength; represents the first operating wavelength; Represents the refractive index of vacuum.
[0064] It should be noted that the first working wavelength in the above calculation formula for the refractive index of the medium to be detected is and the second operating wavelength All units are in nm.
[0065] In a specific embodiment of the present application, when performing refractive index detection, the electromagnetic wave propagation mode of the low crosstalk optical waveguide used is the TE1 mode, and the waveguide core layer includes two waveguides, each waveguide has a width of 800nm, a height of 220nm, and a distance between two adjacent waveguides is 400nm; each substrate unit includes a first substrate and a second substrate; the spacing between two adjacent substrate units and the spacing between adjacent first substrates and second substrates are both 0; the width of the first substrate is 80nm, the width of the second substrate is 40nm, and the height of the first substrate and the height of the second substrate are both 350nm.
[0066] Based on the refractive index detection device provided in the above embodiment, this embodiment further provides a refractive index detection method, which specifically includes: Detecting a first crosstalk value curve of the low crosstalk optical waveguide within a preset working wavelength range, and obtaining a first working wavelength corresponding to a minimum value in the first crosstalk value curve; Filling the medium to be detected between adjacent waveguides of the waveguide core layer in the low crosstalk optical waveguide and on the surface of the waveguide core layer away from the anisotropic substrate layer; Detecting a second crosstalk value curve of the low crosstalk optical waveguide within a preset working wavelength range after being filled with the medium to be detected, and obtaining a second working wavelength corresponding to a minimum value in the second crosstalk value curve; The refractive index of the medium to be detected is calculated based on the first working wavelength, the second working wavelength and the vacuum refractive index.
[0067] Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.
Claims
1. A low crosstalk optical waveguide, characterized in that: include: An anisotropic substrate layer, comprising a plurality of substrate units arranged in a horizontal plane, each of the substrate units comprising a plurality of substrates arranged in a horizontal plane; A waveguide core layer is arranged on the surface of the anisotropic base layer; Wherein, the materials of each substrate in each substrate unit are different dielectric materials; When the propagation mode of the electromagnetic wave is the TE mode, the multiple substrate units and the multiple substrates in each substrate unit are arranged along a direction perpendicular to the propagation direction of the electromagnetic wave; when the propagation mode of the electromagnetic wave is the TM mode, the multiple substrate units and the multiple substrates in each substrate unit are arranged along the propagation direction of the electromagnetic wave.
2. The low crosstalk optical waveguide according to claim 1, characterized in that: Also includes: The silicon dioxide substrate layer is continuously arranged on the surface of the anisotropic substrate layer on a side away from the waveguide core layer.
3. The low crosstalk optical waveguide according to claim 1, characterized in that: The distance between two adjacent base units is 0; and / or The distance between two adjacent substrates in each substrate unit is 0; and / or The height of the substrate unit is 50nm~500nm; and / or The width of the substrate unit is less than 0.13 times of the vacuum wavelength.
4. The low crosstalk optical waveguide according to claim 3, characterized in that: When the propagation mode of the electromagnetic wave is the TE mode, the width of each of the substrate units is smaller than the width of each waveguide in the waveguide core layer, and the length of each of the substrate units is greater than or equal to the length of each waveguide in the waveguide core layer; When the propagation mode of the electromagnetic wave is the TM mode, the sum of the widths of all the substrate units is greater than or equal to the length of each waveguide in the waveguide core layer.
5. The low crosstalk optical waveguide according to claim 1, characterized in that: When the propagation mode of electromagnetic waves is TE0 mode, The width of each waveguide in the waveguide core layer is 440 nm, the height of each waveguide is 220 nm, and the distance between two adjacent waveguides is 400 nm; Each of the substrate units includes a first substrate and a second substrate; The distance between two adjacent substrate units and the distance between the first substrate and the second substrate are both 0; The width of the substrate unit is 120 nm, the width of the first substrate is 80 nm, the width of the second substrate is 40 nm, and the height of the first substrate and the height of the second substrate are both 380 nm.
6. The low crosstalk optical waveguide according to claim 1, characterized in that: When the propagation mode of electromagnetic waves is TM0 mode, The width of each waveguide in the waveguide core layer is 450 nm, the height of each waveguide is 220 nm, and the distance between two adjacent waveguides is 450 nm; Each of the substrate units includes a first substrate and a second substrate; The distance between two adjacent substrate units and the distance between the first substrate and the second substrate are both 0; The width of the first substrate is 100 nm, the width of the second substrate is 100 nm, and the height of the first substrate and the height of the second substrate are both 94 nm.
7. The low crosstalk optical waveguide according to claim 1, characterized in that: When the propagation mode of electromagnetic waves is TE1 mode, The width of each waveguide in the waveguide core layer is 800 nm, the height of each waveguide is 220 nm, and the distance between two adjacent waveguides is 400 nm; Each of the substrate units includes a first substrate and a second substrate; The distance between two adjacent substrate units and the distance between the first substrate and the second substrate are both 0; The width of the first substrate is 80 nm, the width of the second substrate is 40 nm, and the height of the first substrate and the height of the second substrate are both 350 nm.
8. The low crosstalk optical waveguide according to claim 1, characterized in that: The dielectric material includes silicon, silicon dioxide, silicon nitride, aluminum nitride, and titanium dioxide.
9. A refractive index detection device, characterized in that: include: The low crosstalk optical waveguide according to any one of claims 1 to 8; a crosstalk detection device, connected to the low-crosstalk optical waveguide, and used to detect a first crosstalk value curve of the low-crosstalk optical waveguide within a preset working wavelength range; After the medium to be detected is filled between adjacent waveguides of the waveguide core layer in the low crosstalk optical waveguide and on the surface of the waveguide core layer away from the anisotropic substrate layer, a second crosstalk value curve of the low crosstalk optical waveguide within a preset working wavelength range is detected; A host computer, which is in communication connection with the crosstalk detection device, is used to obtain a first operating wavelength corresponding to the minimum value in the first crosstalk value curve, and a second operating wavelength corresponding to the minimum value in the second crosstalk value curve, and calculate the refractive index of the medium to be detected based on the first operating wavelength, the second operating wavelength and the vacuum refractive index; Wherein, the calculation formula of the refractive index of the medium to be detected is: ， in, Indicates the refractive index of the medium to be detected; represents the second operating wavelength; represents the first operating wavelength; Represents the refractive index of vacuum.
10. A refractive index detection method, characterized in that: The method is applied to the refractive index detection device as claimed in claim 9, comprising: Detecting a first crosstalk value curve of the low crosstalk optical waveguide within a preset operating wavelength range, and obtaining a first operating wavelength corresponding to a minimum value in the first crosstalk value curve; Filling a medium to be detected between adjacent waveguides of the waveguide core layer in the low crosstalk optical waveguide and on the surface of the waveguide core layer away from the anisotropic substrate layer; Detecting a second crosstalk value curve of the low crosstalk optical waveguide after being filled with the medium to be detected within a preset working wavelength range, and obtaining a second working wavelength corresponding to a minimum value in the second crosstalk value curve; The refractive index of the medium to be detected is calculated based on the first working wavelength, the second working wavelength and the vacuum refractive index.