Quasi-BIC metasurface-based high-resolution acceleration sensor and measurement method

Abstract

The invention relates to the technical field of grating interference type acceleration sensors, in particular to a high-resolution acceleration sensor based on a quasi-BIC metasurface and a measuring method. The problems that an existing grating interference type acceleration sensor is low in resolution ratio and large in ohmic loss are solved. The invention discloses a high-resolution acceleration sensor based on a quasi-BIC metasurface. The high-resolution acceleration sensor comprises a laser, a beam splitter, an acoustic optical modulator, an electro-optical modulator, an optical circulator, a packaging box, a balanced photoelectric detector, an amplifier and a digital instrument, a light-transmitting micropore is formed in the top wall of the packaging box in a penetrating manner; a sensing unit is packaged in an inner cavity of the packaging box; the sensing unit comprises two silicon supporting blocks, a silicon mass block, a distributed Bragg reflector, four columns of silicon nitride cantilever beams, a transparent substrate and a quasi-BIC metasurface structure. The method is suitable for measuring the acceleration signal.

Description

Technical Field

[0001] The present invention relates to the technical field of grating interferometric acceleration sensors, and in particular to a high-resolution acceleration sensor based on a quasi-BIC metasurface and a measurement method. Background Art

[0002] Grating interferometric accelerometers are widely used in the measurement of acceleration signals because of their strong anti-interference ability. However, in practical applications, the existing grating interferometric accelerometers have the following problems due to their own structural limitations: First, the sensitive unit of the existing grating interferometric accelerometer has a low Q value and a wide line width of the output spectrum, which makes it impossible to accurately measure weak acceleration signals, resulting in low resolution. Second, the sensitive unit of the existing grating interferometric accelerometer contains metal materials, resulting in large ohmic losses. Quasi-BIC (Bound States in the Continuum) is a special resonant mode based on the bound state of the continuous domain in the metasurface, which has an extremely high Q value and an extremely narrow line width, and can greatly improve the interaction between light and matter. This feature makes quasi-BIC have great application potential in improving the resolution of sensors. Based on this, it is necessary to invent a high-resolution accelerometer and a measurement method based on a quasi-BIC metasurface to solve the problems of low resolution and large ohmic loss of the existing grating interferometric accelerometer. Summary of the invention

[0003] In order to solve the problems of low resolution and large ohmic loss of existing grating interferometric acceleration sensors, the present invention provides a high-resolution acceleration sensor based on a quasi-BIC metasurface and a measurement method.

[0004] The present invention is achieved by adopting the following technical solutions:

[0005] A high-resolution acceleration sensor based on a quasi-BIC metasurface, comprising a laser, a beam splitter, an acousto-optic modulator, an electro-optic modulator, an optical circulator, a packaging box, a balanced photodetector, an amplifier, and a digitizer;

[0006] The top wall of the packaging box is provided with a light-transmitting micro-hole; the inner cavity of the packaging box is provided with a sensitive unit; the sensitive unit comprises two silicon support blocks, a silicon mass block, a distributed Bragg reflector, four rows of silicon nitride cantilever beams, a transparent substrate, and a quasi-BIC metasurface structure; the two silicon support blocks are stacked on the inner bottom wall of the packaging box, and the two silicon support blocks are symmetrically distributed; the silicon mass block is located between the two silicon support blocks, and the lower surface of the silicon mass block is higher than the lower surfaces of the two silicon support blocks; the distributed Bragg reflector comprises M silicon nitride layers and M silicon dioxide layers stacked alternately from bottom to top; M is a positive integer, and M≥2; the distributed Bragg reflector is stacked on the upper surface of the silicon mass block, and the upper surface of the distributed Bragg reflector is lower than the upper surfaces of the two silicon support blocks;

[0007] The first row of silicon nitride cantilever beams is connected between the left surface of the silicon mass block and the right surface of the first silicon support block; the second row of silicon nitride cantilever beams is connected between the left surface of the distributed Bragg reflector and the right surface of the first silicon support block; the third row of silicon nitride cantilever beams is connected between the right surface of the silicon mass block and the left surface of the second silicon support block; the fourth row of silicon nitride cantilever beams is connected between the right surface of the distributed Bragg reflector and the left surface of the second silicon support block; the transparent substrate is stacked on the upper surfaces of the two silicon support blocks at the same time; the quasi-BIC supersurface structure includes N wide strip silicon layers and N narrow strip silicon layers stacked on the upper surface of the transparent substrate and arranged in parallel and staggered at equal intervals; N is a positive integer, and N≥2;

[0008] The output end of the laser is connected to the input end of the beam splitter; the first output end of the beam splitter is connected to the first input end of the balanced photodetector through an acousto-optic modulator; the second output end of the beam splitter is connected to the first port of the optical circulator through an electro-optic modulator; the second port of the optical circulator is connected to the light-transmitting microhole on the packaging box; the third port of the optical circulator is connected to the second input end of the balanced photodetector; and the signal output end of the balanced photodetector is connected to the signal input end of the digitizer through an amplifier.

[0009] Each row of silicon nitride cantilever beams includes a plurality of silicon nitride cantilever beams arranged in parallel and equidistantly from front to back; the first row of silicon nitride cantilever beams is connected between the lower edge of the left surface of the silicon mass block and the lower part of the right surface of the first silicon support block; the second row of silicon nitride cantilever beams is connected between the upper left surface of the distributed Bragg reflector and the upper middle part of the right surface of the first silicon support block; the third row of silicon nitride cantilever beams is connected between the lower edge of the right surface of the silicon mass block and the lower part of the left surface of the second silicon support block; the fourth row of silicon nitride cantilever beams is connected between the upper right surface of the distributed Bragg reflector and the upper middle part of the left surface of the second silicon support block.

[0010] The inner wall of the packaging box is attached with a shielding foil layer made of ferromagnetic alloy; the inner cavity of the packaging box is a vacuum cavity; and a convex lens is sealed and embedded in the light-transmitting microhole.

[0011] The thickness of each silicon nitride layer is 284.48 nm; the thickness of each silicon dioxide layer is 156.25 nm.

[0012] The transparent substrate is made of glass.

[0013] The thickness of each wide strip silicon layer and the thickness of each narrow strip silicon layer are both 240 nm; the width of each wide strip silicon layer is both 600 nm; and the width of each narrow strip silicon layer is both 400 nm.

[0014] A high-resolution acceleration measurement method based on a quasi-BIC metasurface (the method is implemented based on a high-resolution acceleration sensor based on a quasi-BIC metasurface described in the present invention), the method is implemented by the following steps:

[0015] First, the sensor is controlled to enter the working mode; the working mode is specifically as follows: the laser emits a detection light, the detection light is incident on the beam splitter, and is divided into two optical signals by the beam splitter: the first optical signal is incident on the balanced photodetector via the acousto-optic modulator; the second optical signal is incident on the upper surface of the distributed Bragg reflector via the electro-optic modulator, the optical circulator, the light-transmitting microholes on the packaging box, the quasi-BIC metasurface structure, and the transparent substrate in sequence, and after being reflected by the upper surface of the distributed Bragg reflector, it is incident on the balanced photodetector via the transparent substrate, the quasi-BIC metasurface structure, the light-transmitting microholes on the packaging box, and the optical circulator in sequence; the two optical signals are converted into electrical signals by the balanced photodetector; the electrical signals are transmitted to the digitizer via the amplifier, and are converted into output spectra by the digitizer;

[0016] In the working mode, when the acceleration signal acts on the silicon mass block, the silicon mass block moves up and down, and drives the distributed Bragg reflector to move up and down, thereby changing the frequency of the output spectrum; the digital instrument monitors the frequency of the output spectrum before and after the acceleration signal acts on the silicon mass block in real time, and substitutes the frequency of the output spectrum before and after the acceleration signal acts on the silicon mass block into the acceleration measurement equation of the sensor, thereby calculating the acceleration; the acceleration measurement equation of the sensor is expressed as follows:

[0017] ;

[0018] Where: represents acceleration; It represents the frequency of the output spectrum after the acceleration signal acts on the silicon mass block; It represents the frequency of the output spectrum before the acceleration signal acts on the silicon mass block; represents the acceleration due to gravity; Indicates the output wavelength of the laser; represents the resonant frequency; , , All are known quantities.

[0019] Compared with the existing grating interferometric acceleration sensor, the present invention has the following advantages: First, the present invention utilizes the characteristics of quasi-BIC with extremely high Q value and extremely narrow line width to design a sensitive unit with higher Q value, and obtains an output spectrum with narrower line width (such as Figure 5 As shown, compared with the output spectrum of the existing grating interferometric acceleration sensor, the output spectrum of the present invention has a narrower line width), thereby achieving accurate measurement of weak acceleration signals, thereby effectively improving the resolution. Second, the sensitive unit of the present invention no longer contains metal materials, but adopts a full dielectric structure, thereby effectively reducing ohmic losses.

[0020] The present invention effectively solves the problems of low resolution and large ohmic loss of the existing grating interference acceleration sensor, and is suitable for measuring acceleration signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the present invention.

[0022] Figure 2 It is a structural schematic diagram of the sensitive unit in the present invention.

[0023] Figure 3 yes Figure 2 Top view of the .

[0024] Figure 4 yes Figure 2 Bottom view of .

[0025] Figure 5 It is a schematic diagram of output spectra of the present invention and the existing grating interferometric acceleration sensor.

[0026] In the figure: 1-laser, 2-beam splitter, 3-acousto-optic modulator, 4-electro-optic modulator, 5-optical circulator, 6-packaging box, 7-silicon support block, 8-silicon mass block, 9-silicon nitride layer, 10-silicon dioxide layer, 11-silicon nitride cantilever beam, 12-transparent substrate, 13-wide strip silicon layer, 14-narrow strip silicon layer, 15-balanced photodetector, 16-amplifier, 17-digitizer. DETAILED DESCRIPTION

[0027] A high-resolution acceleration sensor based on a quasi-BIC metasurface includes a laser 1, a beam splitter 2, an acousto-optic modulator 3, an electro-optic modulator 4, an optical circulator 5, a packaging box 6, a balanced photodetector 15, an amplifier 16, and a digitizer 17;

[0028] The top wall of the packaging box 6 is provided with a light-transmitting micro-hole; the inner cavity of the packaging box 6 is encapsulated with a sensitive unit; the sensitive unit includes two silicon support blocks 7, a silicon mass block 8, a distributed Bragg reflector, four rows of silicon nitride cantilever beams 11, a transparent substrate 12, and a quasi-BIC metasurface structure; the two silicon support blocks 7 are stacked on the inner bottom wall of the packaging box 6, and the two silicon support blocks 7 are symmetrically distributed; the silicon mass block 8 is located between the two silicon support blocks 7, and the lower surface of the silicon mass block 8 is higher than the lower surfaces of the two silicon support blocks 7; the distributed Bragg reflector includes M silicon nitride layers 9 and M silicon dioxide layers 10 stacked together from bottom to top; M is a positive integer, and M≥2; the distributed Bragg reflector is stacked on the upper surface of the silicon mass block 8, and the upper surface of the distributed Bragg reflector is lower than the upper surfaces of the two silicon support blocks 7;

[0029] The first row of silicon nitride cantilever beams 11 are connected between the left surface of the silicon mass block 8 and the right surface of the first silicon support block 7; the second row of silicon nitride cantilever beams 11 are connected between the left surface of the distributed Bragg reflector and the right surface of the first silicon support block 7; the third row of silicon nitride cantilever beams 11 are connected between the right surface of the silicon mass block 8 and the left surface of the second silicon support block 7; the fourth row of silicon nitride cantilever beams 11 are connected between the right surface of the distributed Bragg reflector and the left surface of the second silicon support block 7; the transparent substrate 12 is stacked on the upper surfaces of the two silicon support blocks 7 at the same time; the quasi-BIC supersurface structure includes N wide strip silicon layers 13 and N narrow strip silicon layers 14 stacked on the upper surface of the transparent substrate 12 and arranged in parallel in an equidistant staggered manner; N is a positive integer, and N≥2;

[0030] The output end of the laser 1 is connected to the input end of the beam splitter 2; the first output end of the beam splitter 2 is connected to the first input end of the balanced photodetector 15 through the acousto-optic modulator 3; the second output end of the beam splitter 2 is connected to the first port of the optical circulator 5 through the electro-optic modulator 4; the second port of the optical circulator 5 is connected to the light-transmitting microhole on the packaging box 6; the third port of the optical circulator 5 is connected to the second input end of the balanced photodetector 15; the signal output end of the balanced photodetector 15 is connected to the signal input end of the digitizer 17 through the amplifier 16.

[0031] Each row of silicon nitride cantilever beams 11 includes a plurality of silicon nitride cantilever beams 11 equidistantly arranged in parallel from front to back; the first row of silicon nitride cantilever beams 11 is connected between the lower edge of the left surface of the silicon mass block 8 and the lower part of the right surface of the first silicon support block 7; the second row of silicon nitride cantilever beams 11 is connected between the upper left surface of the distributed Bragg reflector and the upper middle part of the right surface of the first silicon support block 7; the third row of silicon nitride cantilever beams 11 is connected between the lower edge of the right surface of the silicon mass block 8 and the lower part of the left surface of the second silicon support block 7; the fourth row of silicon nitride cantilever beams 11 is connected between the upper right surface of the distributed Bragg reflector and the upper middle part of the left surface of the second silicon support block 7.

[0032] The inner wall of the packaging box 6 is attached with a shielding foil layer made of ferromagnetic alloy; the inner cavity of the packaging box 6 is a vacuum cavity; and a convex lens is sealed and embedded in the light-transmitting microhole.

[0033] The thickness of each silicon nitride layer 9 is 284.48 nm; the thickness of each silicon dioxide layer 10 is 156.25 nm.

[0034] The transparent substrate 12 is made of glass.

[0035] The thickness of each wide strip silicon layer 13 and the thickness of each narrow strip silicon layer 14 are both 240 nm; the width of each wide strip silicon layer 13 is both 600 nm; and the width of each narrow strip silicon layer 14 is both 400 nm.

[0036] A high-resolution acceleration measurement method based on a quasi-BIC metasurface (the method is implemented based on a high-resolution acceleration sensor based on a quasi-BIC metasurface described in the present invention), the method is implemented by the following steps:

[0037] First, the sensor is controlled to enter the working mode; the working mode is specifically as follows: the laser 1 emits a detection light, the detection light is incident on the beam splitter 2, and is divided into two optical signals by the beam splitter 2: the first optical signal is incident on the balanced photodetector 15 via the acousto-optic modulator 3; the second optical signal is incident on the upper surface of the distributed Bragg reflector via the electro-optic modulator 4, the optical circulator 5, the light-transmitting microholes on the packaging box 6, the quasi-BIC metasurface structure, and the transparent substrate 12 in sequence, and after being reflected by the upper surface of the distributed Bragg reflector, it is incident on the balanced photodetector 15 via the transparent substrate 12, the quasi-BIC metasurface structure, the light-transmitting microholes on the packaging box 6, and the optical circulator 5 in sequence; the two optical signals are converted into electrical signals by the balanced photodetector 15; the electrical signals are transmitted to the digitizer 17 via the amplifier 16, and are converted into an output spectrum by the digitizer 17;

[0038] In the working mode, when the acceleration signal acts on the silicon mass block 8, the silicon mass block 8 moves up and down, and drives the distributed Bragg reflector to move up and down, thereby changing the frequency of the output spectrum; the digital instrument 17 monitors the frequency of the output spectrum before and after the acceleration signal acts on the silicon mass block 8 in real time, and substitutes the frequency of the output spectrum before and after the acceleration signal acts on the silicon mass block 8 into the acceleration measurement equation of the sensor, thereby calculating the acceleration; the acceleration measurement equation of the sensor is expressed as follows:

[0039] ;

[0040] Where: represents acceleration; represents the frequency of the output spectrum after the acceleration signal acts on the silicon mass block 8; represents the frequency of the output spectrum before the acceleration signal acts on the silicon mass block 8; represents the acceleration due to gravity; represents the output wavelength of laser 1; represents the resonant frequency; , , All are known quantities.

[0041] Although the specific embodiments of the present invention are described above, it should be understood by those skilled in the art that these are only examples, and the protection scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A high-resolution acceleration sensor based on a quasi-BIC metasurface, characterized in that: It includes a laser (1), a beam splitter (2), an acousto-optic modulator (3), an electro-optic modulator (4), an optical circulator (5), a packaging box (6), a balanced photodetector (15), an amplifier (16), and a digitizer (17); The top wall of the packaging box (6) is provided with a light-transmitting micro-hole; the inner cavity of the packaging box (6) encapsulates a sensitive unit; the sensitive unit comprises two silicon support blocks (7), a silicon mass block (8), a distributed Bragg reflector, four rows of silicon nitride cantilever beams (11), a transparent substrate (12), and a quasi-BIC metasurface structure; the two silicon support blocks (7) are stacked on the inner bottom wall of the packaging box (6), and the two silicon support blocks (7) are symmetrically distributed; the silicon mass block (8) is located between the two silicon support blocks (7), and the lower surface of the silicon mass block (8) is higher than the lower surfaces of the two silicon support blocks (7); the distributed Bragg reflector comprises M silicon nitride layers (9) and M silicon dioxide layers (10) stacked together from bottom to top; M is a positive integer, and M≥2; the distributed Bragg reflector is stacked on the upper surface of the silicon mass block (8), and the upper surface of the distributed Bragg reflector is lower than the upper surfaces of the two silicon support blocks (7); The first row of silicon nitride cantilever beams (11) are connected between the left surface of the silicon mass block (8) and the right surface of the first silicon support block (7); the second row of silicon nitride cantilever beams (11) are connected between the left surface of the distributed Bragg reflector and the right surface of the first silicon support block (7); the third row of silicon nitride cantilever beams (11) are connected between the right surface of the silicon mass block (8) and the left surface of the second silicon support block (7); the fourth row of silicon nitride cantilever beams (11) are connected between the right surface of the distributed Bragg reflector and the left surface of the second silicon support block (7); the transparent substrate (12) is stacked on the upper surfaces of the two silicon support blocks (7) at the same time; the quasi-BIC supersurface structure comprises N wide strip silicon layers (13) and N narrow strip silicon layers (14) which are stacked on the upper surface of the transparent substrate (12) and are arranged in parallel and staggered at equal intervals; N is a positive integer, and N≥2; The output end of the laser (1) is connected to the input end of the beam splitter (2); the first output end of the beam splitter (2) is connected to the first input end of the balanced photodetector (15) through an acousto-optic modulator (3); the second output end of the beam splitter (2) is connected to the first port of the optical circulator (5) through an electro-optic modulator (4); the second port of the optical circulator (5) is connected to the light-transmitting microhole on the packaging box (6); the third port of the optical circulator (5) is connected to the second input end of the balanced photodetector (15); and the signal output end of the balanced photodetector (15) is connected to the signal input end of the digital instrument (17) through an amplifier (16).

2. A high-resolution acceleration sensor based on a quasi-BIC metasurface according to claim 1, characterized in that: Each row of silicon nitride cantilever beams (11) comprises a plurality of silicon nitride cantilever beams (11) arranged in parallel and equidistant from front to back; the first row of silicon nitride cantilever beams (11) is connected between the lower edge of the left surface of the silicon mass block (8) and the lower part of the right surface of the first silicon support block (7); the second row of silicon nitride cantilever beams (11) is connected between the upper left surface of the distributed Bragg reflector and the middle upper part of the right surface of the first silicon support block (7); the third row of silicon nitride cantilever beams (11) is connected between the lower edge of the right surface of the silicon mass block (8) and the lower part of the left surface of the second silicon support block (7); and the fourth row of silicon nitride cantilever beams (11) is connected between the upper right surface of the distributed Bragg reflector and the middle upper part of the left surface of the second silicon support block (7).

3. A high-resolution acceleration sensor based on a quasi-BIC metasurface according to claim 1, characterized in that: A shielding foil layer made of ferromagnetic alloy is attached to the inner wall of the packaging box (6); the inner cavity of the packaging box (6) is a vacuum cavity; and a convex lens is sealed and embedded in the light-transmitting microhole.

4. A high-resolution acceleration sensor based on a quasi-BIC metasurface according to claim 1, characterized in that: The thickness of each silicon nitride layer (9) is 284.48 nm; the thickness of each silicon dioxide layer (10) is 156.25 nm.

5. The high-resolution acceleration sensor based on the quasi-BIC metasurface according to claim 1, characterized in that: The transparent substrate (12) is made of glass.

6. A high-resolution acceleration sensor based on a quasi-BIC metasurface according to claim 1, characterized in that: The thickness of each wide strip silicon layer (13) and the thickness of each narrow strip silicon layer (14) are both 240 nm; the width of each wide strip silicon layer (13) is both 600 nm; and the width of each narrow strip silicon layer (14) is both 400 nm.

7. A high-resolution acceleration measurement method based on a quasi-BIC metasurface, the method being implemented based on a high-resolution acceleration sensor based on a quasi-BIC metasurface as claimed in claim 1, characterized in that: This method is implemented by the following steps: First, the sensor is controlled to enter a working mode; the working mode is specifically as follows: the laser (1) emits a detection light, the detection light is incident on the beam splitter (2), and is divided into two optical signals by the beam splitter (2): the first optical signal is incident on the balanced photodetector (15) via the acousto-optic modulator (3); the second optical signal is incident on the upper surface of the distributed Bragg reflector via the electro-optic modulator (4), the optical circulator (5), the light-transmitting microhole on the packaging box (6), the quasi-BIC metasurface structure, and the transparent substrate (12) in sequence, and after being reflected by the upper surface of the distributed Bragg reflector, it is incident on the balanced photodetector (15) via the transparent substrate (12), the quasi-BIC metasurface structure, the light-transmitting microhole on the packaging box (6), and the optical circulator (5) in sequence; the two optical signals are converted into electrical signals by the balanced photodetector (15); the electrical signals are transmitted to the digitizer (17) via the amplifier (16), and are converted into an output spectrum by the digitizer (17); In the working mode, when the acceleration signal acts on the silicon mass block (8), the silicon mass block (8) moves up and down, and drives the distributed Bragg reflector to move up and down, thereby changing the frequency of the output spectrum; the digital instrument (17) monitors the frequency of the output spectrum before and after the acceleration signal acts on the silicon mass block (8) in real time, and substitutes the frequency of the output spectrum before and after the acceleration signal acts on the silicon mass block (8) into the acceleration measurement equation of the sensor, thereby calculating the acceleration; the acceleration measurement equation of the sensor is expressed as follows: ； Where: represents acceleration; represents the frequency of the output spectrum after the acceleration signal acts on the silicon mass block (8); represents the frequency of the output spectrum before the acceleration signal acts on the silicon mass block (8); represents the acceleration due to gravity; represents the output wavelength of the laser (1); represents the resonant frequency; , , All are known quantities.

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