Silicon-based groove type annular resonant cavity for sound pressure sensing and preparation method of silicon-based groove type annular resonant cavity
By adopting a groove structure and a planar waveguide grating in a silicon-based annular resonant cavity and using the evanescent field effect for light field coupling, the problems of weak local capacity and large coupling loss of traditional annular resonant cavity are solved, and higher sensitivity is achieved.
Patent Information
- Application Number
- CN202411359768.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-27
- Publication Date
- 2025-02-25
AI Technical Summary
The traditional all-pass silicon-based annular resonant cavity has problems such as weak localization of the light field and large coupling loss, resulting in low sensitivity.
The silicon-based groove-type annular resonant cavity structure is adopted, and the light field coupling is achieved by etching the plane waveguide grating on both sides of the straight waveguide and evanescent field effect in the groove-type annular resonant cavity to achieve the function of light constraining in the intermediate groove.
It significantly enhances the local capacity of the light field, improves the quality factor of the resonant cavity and the interaction ability of the light field and sound pressure, thereby improving the sensitivity of the sensor.
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Figure CN119511459A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of sensor devices, and in particular relates to a silicon-based slot-type ring resonator for sound pressure sensing and a preparation method thereof. Background Art
[0002] Since most of the underwater detection in the ocean is done by acoustic wave detection, it is of great significance to develop high-performance underwater acoustic sensor equipment. The acoustic pressure sensor device based on the silicon-based slot ring resonator uses polymer material SU8 as the upper cladding. The low Young's modulus makes it perform well in terms of acoustic performance. When the density of the upper cladding changes due to the sound pressure, the refractive index of the upper cladding and the core layer of the optical waveguide will also change. According to the effective refractive index method, the refractive index of the lower cladding remains unchanged, and the change in the refractive index of the upper cladding and the core layer will cause the effective refractive index of the waveguide to change, causing the resonant wavelength to shift. The change in the detection wavelength shift is used to detect the change in the underwater acoustic signal to be measured.
[0003] The traditional all-through silicon-based ring resonator structure has problems such as weak light field localization ability, large coupling loss, low sensitivity, and large coupling loss. Summary of the invention
[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a silicon-based slot ring resonator for sound pressure sensing and a method for preparing the same. The present invention can solve the problems existing in the prior art.
[0005] The technical solution of the present invention:
[0006] According to a first aspect, a silicon-based slot ring resonator core layer for sound pressure sensing is provided, comprising an input plane waveguide grating, a slot ring resonator, a straight waveguide and an output plane waveguide grating, wherein the input plane waveguide grating is connected to the input end of the straight waveguide, the output end of the straight waveguide is connected to the output plane waveguide grating, the slot ring resonator is a resonant cavity composed of two concentric rings, the slot ring resonator is located above the straight waveguide, and the middle is a coupling region.
[0007] Furthermore, the coupling region has a size of 80 to 120 nm.
[0008] Furthermore, the core layer thickness of the silicon-based slot ring resonator for sound pressure sensing is 220-280 nm, and the core layer width is 450-800 nm.
[0009] Furthermore, the period of the input planar waveguide grating and the output planar waveguide grating is 600-800 nm, and the duty ratio is 1:1.
[0010] Furthermore, the radius of the inner ring of the resonant cavity is 15 to 25 μm, and the groove spacing between the inner and outer rings is 80 to 100 nm.
[0011] According to a second aspect, a silicon-based slot ring resonator for acoustic pressure sensing is provided, comprising an upper cladding layer, the silicon-based slot ring resonator core layer and a lower cladding layer connected in sequence.
[0012] Furthermore, the upper cladding material is SU8, the core layer material of the silicon-based slot ring resonator is silicon, and the lower cladding material is silicon dioxide.
[0013] Furthermore, the SU8 is used as the upper cladding layer with a thickness of 0.5 to 2 μm, and the silicon dioxide is used as the lower cladding layer with a thickness of 1 to 3 μm.
[0014] According to a third aspect, a method for preparing the above-mentioned silicon-based slot ring resonator for sound pressure sensing is provided, comprising the following steps:
[0015] A silicon dioxide mask layer is grown on the SOI substrate as a lower cladding layer;
[0016] The mask with the grooved ring resonator and the straight waveguide pattern is transferred to the silicon dioxide surface to form a mask layer, and then the pattern on the mask is transferred to the photoresist through exposure and development;
[0017] ICP etching is used to etch the mask layer pattern to remove excess photoresist, and ICP etching is used to form the slot-type ring resonator and the straight waveguide to form the slot-type waveguide and the straight waveguide;
[0018] Align the grating diffraction with the straight waveguide respectively, perform electron beam lithography to form the input planar waveguide grating and the output planar waveguide grating, and then anneal at high temperature for 2 to 3 hours;
[0019] A certain thickness of polymer material SU8 is spin-coated on the surface of the core layer of the silicon-based slot ring resonator, and then thinned to obtain SU8 of corresponding size as an upper cladding layer.
[0020] The beneficial effects of the present invention compared with the prior art are as follows:
[0021] (1) The silicon-based slot ring resonator and straight waveguide of the present invention adopt silicon-based etching technology to etch planar waveguide gratings on both sides of the straight waveguide, thereby achieving low-loss coupling with a single-mode optical fiber;
[0022] (2) Based on the discontinuous characteristics of the electric field at the interface with high refractive index difference, the slot ring resonator can confine light in the middle groove and realize the function of light transmission in the low refractive index area. When light enters the straight waveguide from the planar waveguide grating, an exponentially decaying evanescent field will be formed on the waveguide surface. When the light is transmitted to the coupling area, part of the light will enter the ring resonator. Due to the evanescent field effect, the straight waveguide and the ring resonator produce evanescent field coupling. The light that meets the resonance conditions will be confined in the middle groove of the ring resonator, forming a higher light energy density. The light that does not meet the resonance conditions will be output from the output end of the straight waveguide. Repeating this cycle will form a stronger light energy localization effect in the groove. Compared with the traditional structure, the slot waveguide structure has significantly enhanced the light field localization capability, effectively improving the quality factor of the resonant cavity, and enhancing the interaction ability between the light field and the sound pressure, which can improve the sensitivity of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0024] Figure 1 A schematic diagram of a planar structure of a silicon-based slot ring resonator for sound pressure sensing according to an embodiment of the present invention is shown;
[0025] Figure 2 A schematic diagram of the three-dimensional structure of a silicon-based slot ring resonator device provided according to an embodiment of the present invention is shown;
[0026] Figure 3 A schematic cross-sectional view of a silicon-based slot ring resonator waveguide provided in an embodiment of the present invention is shown;
[0027] Figure 4 A schematic diagram showing the relationship between the effective refractive index and the sound pressure change of the silicon-based slot ring resonator provided in an embodiment of the present invention is shown;
[0028] Figure 5 A schematic diagram of a spectrum curve of a silicon-based slot ring resonator provided according to an embodiment of the present invention is shown. Explanation of the reference numerals in the figure: 1, input planar waveguide grating, 2, input straight waveguide, 3, output straight waveguide, 4, output planar waveguide grating, 5, slot ring resonator, 6, coupling region, 7, groove region, 8, lower cladding, 9, core layer, 10, upper cladding. DETAILED DESCRIPTION
[0029] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0030] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.
[0031] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.
[0032] like Figure 1 As shown, according to an embodiment of the first aspect of the present invention, a silicon-based slot ring resonator core layer for sound pressure sensing is provided, comprising an input plane waveguide grating, a slot ring resonator, a straight waveguide and an output plane waveguide grating, wherein the input plane waveguide grating is connected to the input end of the straight waveguide, the output end of the straight waveguide is connected to the output plane waveguide grating, the slot ring resonator is a resonant cavity composed of two concentric rings, the slot ring resonator is located above the straight waveguide, and the middle is a coupling region.
[0033] Through this setting, the slot ring resonator can confine light in the middle groove based on the discontinuous characteristics of the electric field at the interface with high refractive index difference, thereby realizing the function of light transmission in the low refractive index area. After the light enters the straight waveguide from the planar waveguide grating, an exponentially decaying evanescent field will be formed on the surface of the waveguide. When the light is transmitted to the coupling area, part of the light will enter the ring resonator. Due to the evanescent field effect, the straight waveguide and the ring resonator produce evanescent field coupling. The light that meets the resonance conditions will be confined to the middle groove of the ring resonator, forming a higher light energy density. The light that does not meet the resonance conditions will be output from the output end of the straight waveguide. Repeating this cycle will form a stronger light energy localization effect in the groove. Compared with the traditional structure, the slot waveguide structure has significantly enhanced the light field localization capability, effectively improving the quality factor of the resonant cavity, and enhancing the interaction ability between the light field and the sound pressure, which can improve the sensitivity of the sensor.
[0034] Further in one embodiment, the coupling region size is 80-120 nm.
[0035] Further in one embodiment, a silicon-based slot ring resonator for sound pressure sensing has a core layer thickness of 220-280 nm and a core layer width of 450-800 nm.
[0036] Further in one embodiment, the period of the input planar waveguide grating and the output planar waveguide grating is 600-800 nm, and the duty cycle is 1:1.
[0037] In a further embodiment, the radius of the inner ring of the silicon-based slot ring resonator is 15-25 μm, and the slot spacing between the inner and outer rings is 80-100 nm.
[0038] According to a second aspect of the embodiment, a silicon-based slot ring resonator for sound pressure sensing is provided, comprising an upper cladding, the silicon-based slot ring resonator core layer and a lower cladding connected in sequence.
[0039] Further in one embodiment, the upper cladding material is SU8, the core material of the silicon-based slot ring resonator is silicon, and the lower cladding material is silicon dioxide.
[0040] In a further embodiment, SU8 is used as the upper cladding layer with a thickness of 0.5 to 2 μm, and silicon dioxide is used as the lower cladding layer with a thickness of 1 to 3 μm.
[0041] According to a third aspect of the embodiment, a method for preparing the above-mentioned silicon-based slot ring resonator for sound pressure sensing is provided, comprising the following steps:
[0042] A silicon dioxide mask layer is grown on the SOI substrate as a lower cladding layer;
[0043] The mask with the grooved ring resonator and the straight waveguide pattern is transferred to the silicon dioxide surface to form a mask layer, and then the pattern on the mask is transferred to the photoresist through exposure and development;
[0044] ICP etching is used to etch the mask layer pattern to remove excess photoresist, and ICP etching is used to form the slot-type ring resonator and the straight waveguide to form the slot-type waveguide and the straight waveguide;
[0045] Align the grating diffraction with the straight waveguide respectively, perform electron beam lithography to form the input planar waveguide grating and the output planar waveguide grating, and then anneal at high temperature for 2 to 3 hours;
[0046] A certain thickness of polymer material SU8 is spin-coated on the surface of the core layer of the silicon-based slot ring resonator, and then thinned to obtain SU8 of corresponding size as an upper cladding layer.
[0047] Working principle: When light is transmitted from the input straight waveguide to the coupling region, the straight waveguide and the slot ring resonator generate evanescent field coupling. Part of the light field enters the resonator groove and has the same phase after one cycle. The light in the straight waveguide and the light in the groove will resonate. The light in the slot ring resonator satisfies the resonance condition given by formula (1).
[0048] mλ=n eff L,m=1,2,3... (1)
[0049] Among them, m is the resonance order, λ is the resonance wavelength, and n eff is the effective refractive index, and L is the circumference of the slot ring resonator.
[0050] When the upper cladding of the optical waveguide slot ring resonator is deformed due to the sound pressure, the refractive index of the upper cladding and core of the optical waveguide will also change. Since the refractive index of the lower cladding remains unchanged, the change in the refractive index of the upper cladding and core will cause the effective refractive index of the waveguide to change. The relationship between the effective refractive index and the change in the refractive index of the core is:
[0051]
[0052] Where k0 is the wave number, k x , k y is the resonance coefficient of the core layer along the x and y directions, and n1 is the refractive index of the waveguide core layer under the action of sound pressure.
[0053] According to the effective refractive index theory, there is a linear relationship between the sound pressure and the effective refractive index. The effective refractive index of the waveguide increases with the increase of the sound pressure. According to formulas (1) and (2), the refractive index of the core layer will cause the effective refractive index to change. When the effective refractive index increases, the resonant wavelength will also redshift. The sensor sensitivity is defined as:
[0054]
[0055] Among them, S is sensitivity, T is light transmission efficiency, Q is quality factor, and P is sound pressure. Therefore, according to formulas (1) to (3), the sensor sensitivity is positively correlated with the effective refractive index and quality factor.
[0056] In order to have a further understanding of the silicon-based slot ring resonator for sound pressure sensing and the preparation method thereof provided by the present invention, a detailed description is given below in conjunction with specific examples and drawings.
[0057] like Figure 1 , Figure 2 As shown, the silicon-based slot ring resonator device for sound pressure sensing of the present invention is composed of an input plane waveguide grating 1, an input straight waveguide 2, a slot ring resonator 5, an output plane waveguide grating 4, an output straight waveguide 3, a coupling region 6, and a slot region 7. The input plane waveguide grating 1 is connected to the input straight waveguide 2, the output plane waveguide grating 4 is connected to the output straight waveguide 3, the input straight waveguide 2 and the slot ring resonator 5 are connected through the coupling region 6, the output straight waveguide 3 and the slot ring resonator 5 are connected through the coupling region 6, and the slot region 7 is the middle spacing region of the slot ring resonator.
[0058] The silicon-based slot ring resonator is composed of a planar waveguide grating, a straight waveguide and a silicon-based slot waveguide ring resonator. Specifically, the cross section of the silicon-based slot ring resonator is as follows: Figure 3 As shown, from top to bottom are the upper cladding 10, the core layer 9, and the lower cladding 8, wherein the lower cladding material is silicon dioxide, the upper cladding material is SU8 with a thickness of 1 μm, the core layer material is silicon with a thickness of 220 nm and a width of 450 nm, the inner ring radius of the slot ring resonator is 20 μm, and the slot spacing is 100 nm.
[0059] The method for preparing the silicon-based slot ring resonator device for sound pressure sensing of the present invention is as follows:
[0060] In the first step, a layer of silicon dioxide is oxidized and grown on the SOI substrate as a mask layer for subsequent etching, with a thickness of 1μm; the mask with the core layer pattern is transferred to the surface of the silicon dioxide to form a mask layer, and an appropriate amount of photoresist is applied for uniform coating. The drawn mask pattern is introduced into the electron beam lithography system, and is transferred to the photoresist through exposure and development. The mask layer pattern is etched using ICP etching technology to remove excess photoresist, and then the silicon waveguide is etched using ICP to form the core layer shape. The etching time is 25s and the etching depth is 220nm.
[0061] In the second step, the grating diffraction is aligned with the input straight waveguide and the output straight waveguide, and electron beam lithography is performed at the designed position. The grating is etched by ICP and annealed at high temperature for 3 hours to reduce the surface roughness of the waveguide. The grating period is 600nm and the duty cycle is 1:1.
[0062] In the third step, a certain thickness of polymer material SU8 is spin-coated on the grooves on the surface of the core layer to perform thinning treatment, and the thickness of the upper cladding layer is 1μm.
[0063] Resonance spectrum and sound pressure test of silicon-based slot ring resonator:
[0064] like Figure 4 As shown, the response curve and acoustic wave signal curve of the acoustic sensing test using a silicon-based slot ring resonator as a sensor device are shown. The silicon-based slot ring resonator is placed in a water environment, and a sinusoidal sound pressure signal with a frequency of 1kHz is applied to the sensor chip.
[0065] like Figure 5 As shown in the figure, the response curve and acoustic wave signal curve of the acoustic sensing test using the traditional all-through silicon-based ring resonator as the sensor device are shown. The all-through silicon-based ring resonator is placed in a water environment, and a sinusoidal sound pressure signal with a frequency of 1kHz is applied to the sensor chip.
[0066] The experimental results verify the feasibility of using the silicon-based slot ring resonator device proposed in the present invention for acoustic sensing.
[0067] In summary, the silicon-based slot ring resonator for sound pressure sensing and the preparation method thereof provided by the present invention have at least the following advantages over the prior art:
[0068] (1) The silicon-based slot ring resonator and straight waveguide of the present invention adopt silicon-based etching technology to etch planar waveguide gratings on both sides of the straight waveguide, thereby achieving low-loss coupling with a single-mode optical fiber;
[0069] (2) Based on the discontinuous characteristics of the electric field at the interface with high refractive index difference, the slot ring resonator can confine light in the middle groove and realize the function of light transmission in the low refractive index area. When light enters the straight waveguide from the planar waveguide grating, an exponentially decaying evanescent field will be formed on the waveguide surface. When the light is transmitted to the coupling area, part of the light will enter the ring resonator. Due to the evanescent field effect, the straight waveguide and the ring resonator produce evanescent field coupling. The light that meets the resonance conditions will be confined in the middle groove of the ring resonator, forming a higher light energy density. The light that does not meet the resonance conditions will be output from the output end of the straight waveguide. Repeating this cycle will form a stronger light energy localization effect in the groove. Compared with the traditional structure, the slot waveguide structure has significantly enhanced the light field localization capability, effectively improving the quality factor of the resonant cavity, and enhancing the interaction ability between the light field and the sound pressure, which can improve the sensitivity of the sensor.
[0070] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" may include both "above" and "below". The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.
[0071] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.
[0072] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A silicon-based slot ring resonator core for sound pressure sensing, characterized in that: It includes an input plane waveguide grating, a slot ring resonant cavity, a straight waveguide and an output plane waveguide grating. The input plane waveguide grating is connected to the input end of the straight waveguide, the output end of the straight waveguide is connected to the output plane waveguide grating, the slot ring resonant cavity is a resonant cavity composed of two concentric rings, the slot ring resonant cavity is located above the straight waveguide, and the middle is a coupling area.
2. The silicon-based slot ring resonator core layer for sound pressure sensing according to claim 1, characterized in that: The coupling region has a size of 80 to 120 nm.
3. The silicon-based slot ring resonator core layer for sound pressure sensing according to claim 2, characterized in that: The core layer thickness of the silicon-based slot-type ring resonant cavity used for sound pressure sensing is 220-280 nm, and the core layer width is 450-800 nm.
4. The silicon-based slot ring resonator core layer for sound pressure sensing according to claim 3, characterized in that: The periods of the input planar waveguide grating and the output planar waveguide grating are 600-800nm, and the duty ratio is 1:
1.
5. The silicon-based slot ring resonator core layer for sound pressure sensing according to claim 4, characterized in that: The radius of the inner ring of the resonant cavity is 15-25 μm, and the groove spacing between the inner and outer rings is 80-100 nm.
6. A silicon-based slot ring resonator for sound pressure sensing, characterized in that: It comprises an upper cladding layer, a silicon-based slot ring resonator core layer and a lower cladding layer which are connected in sequence.
7. A silicon-based slot ring resonator for sound pressure sensing as claimed in claim 6, characterized in that: The upper cladding material is SU8, the core layer material of the silicon-based slot ring resonator is silicon, and the lower cladding material is silicon dioxide.
8. A silicon-based slot ring resonator for sound pressure sensing as claimed in claim 7, characterized in that: The SU8 is used as the upper cladding layer with a thickness of 0.5 to 2 μm, and the silicon dioxide is used as the lower cladding layer with a thickness of 1 to 3 μm.
9. A method for preparing a silicon-based slot ring resonator for sound pressure sensing according to any one of claims 6 to 8, characterized in that: The method comprises the following steps: A silicon dioxide mask layer is grown on the SOI substrate as a lower cladding layer; The mask with the grooved ring resonator and the straight waveguide pattern is transferred to the silicon dioxide surface to form a mask layer, and then the pattern on the mask is transferred to the photoresist through exposure and development; ICP etching is used to etch the mask layer pattern to remove excess photoresist, and ICP etching is used to form the slot-type ring resonator and the straight waveguide to form the slot-type waveguide and the straight waveguide; Align the grating diffraction with the straight waveguide respectively, perform electron beam lithography to form the input planar waveguide grating and the output planar waveguide grating, and then anneal at high temperature for 2 to 3 hours; A certain thickness of polymer material SU8 is spin-coated on the surface of the core layer of the silicon-based slot ring resonator, and then thinned to obtain SU8 of corresponding size as an upper cladding layer.