Light ray angle sensor and light ray angle sensing method

Abstract

This invention discloses a light angle sensor and a light angle sensing method. The light angle sensing method includes the following steps: (1) Based on a one-dimensional double-layer YIG photonic crystal cell, the spacing between the scatterers in the upper and lower layers is changed to generate two structural units: Type I (near top, far bottom) and Type II (far top, near bottom); (2) The spacing between the scatterers is adjusted so that the energy bands of the two structures are the same, and then four cells from each structure are spliced ​​together to form a parallel plate waveguide, forming a topological interface in the middle; (3) The waveguide energy state number is calculated, the band gap with two boundary states is found, the transmission spectrum is calculated, and two Fano curves are formed; (4) The light incident angle is changed, and the relationship between the total extinction ratio and the incident angle of the two Fano curves is calculated. The curves show the high sensitivity sensing characteristics of the light incident angle. This method not only enriches the research on topological boundary states, but also provides a simpler method for realizing high-sensitivity light angle sensing.

Description

Technical Field

[0001] This invention relates to the field of optical technology, and in particular to a light angle sensor and a light angle sensing method. Background Technology

[0002] Solar energy is currently the most widely distributed and abundant renewable energy source available to humankind. Converting solar energy into electricity requires photovoltaic (PV) power generation technology. However, the angle of sunlight radiation changes constantly throughout the day, causing the area of ​​the PV module receiving sunlight to also change, thus affecting the PV power generation efficiency. Therefore, to achieve high solar power generation efficiency, a light angle sensor is needed in the solar power generation device to constantly sense changes in the light angle and adjust the angle of the PV module accordingly. Since the change in the angle of sunlight is relatively slow, to prevent the PV module's angle adjustment from lagging too much behind the change in the light angle, a highly sensitive light angle sensor capable of sensing even minute deflections of the light is needed. This allows the adjustment components in the PV device to keep up with the changes in the light angle. Furthermore, to reduce the cost of PV power generation, a simpler structure for the light angle sensor is more beneficial for practical applications. In addition, the monitoring and control of light angles is extremely important in the field of microscopic characterization. The incident angle of the light source affects the microscope's observation of the sample. For example, when observing a chip using a stereomicroscope, coaxial light reveals more information about the sample surface, while oblique incident light reveals more information about the sample surface contour. Therefore, in some detections with very high requirements for microscopic characterization, the monitoring and adjustment of the light source becomes crucial. This includes having sufficiently sensitive sensing for minute changes in the light angle to make corresponding fine adjustments to the light source. In optics, there are many methods for measuring the incident angle of light. Among them, measuring the light angle using a spectrometer is the most common method. However, the basic optical structure of a spectrometer is relatively complex, and the adjustment steps during use are cumbersome, making it unsuitable for combination with other instruments. Currently, most systems for measuring the angle of light are not simple enough and struggle to achieve high-sensitivity sensing within a small deflection angle range. Therefore, finding a method with a simple system architecture that can achieve high-sensitivity sensing of minute angle deflections of light is essential. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a light angle sensor that can achieve high sensitivity sensing of minute angle deflections of light; another purpose of this invention is to provide a light angle sensing method that is highly sensitive and simple.

[0004] Technical Solution: The present invention provides a light angle sensor, comprising a parallel plate waveguide with a topological structure. The parallel plate waveguide consists of a parallel plate waveguide and a magnetic field applied to it. Under the action of the magnetic field, two topological boundary states are generated in the band gap of the parallel plate waveguide. The parallel plate waveguide is composed of a one-dimensional double-layer photonic crystal. The one-dimensional double-layer photonic crystal is formed by piecing together n sequentially distributed Type I cells and n sequentially distributed Type II cells. After rotating the Type I cells 180° around their geometric center, their structures are identical to those of the Type II cells. The magnetic field is applied perpendicular to the plane of the scatterer structure to change the permeability of the one-dimensional double-layer photonic crystal to a gyromagnetic form. The two types of cells have identical band structures. The piecing together of n Type I cells and n Type II cells forms the parallel plate waveguide with a topological structure.

[0005] As a further improvement to the above scheme, each unit cell in the one-dimensional bilayer photonic crystal consists of four scatterers. The scatterers within the cell are divided into upper and lower layers, with two scatterers in each layer. The vertical distance between the two layers of scatterers remains constant. The Type I cell is characterized by a smaller distance between the two scatterers in the upper layer than between the two scatterers in the lower layer. The Type II cell is characterized by a larger distance between the two scatterers in the upper layer than between the two scatterers in the lower layer.

[0006] As a further improvement to the above scheme, the cell lattice constant of the parallel plate waveguide is a = 22 cm, the width between the upper and lower hard boundaries of the waveguide is h = 29.6 cm, the spacing between scatterers in the upper layer of the Type I cell in the waveguide is d1 = 6.6 cm, the spacing between scatterers in the lower layer is d2 = 15.4 cm, the spacing between scatterers in the upper layer of the Type II cell in the waveguide is d3 = 15.4 cm, and the spacing between scatterers in the lower layer is d4 = 6.6 cm.

[0007] Preferably, the radius of the scatterer in the unit cell is 2.67 cm, and the vertical distance between the horizontal center lines of the upper and lower layers of scatterers is fixed at 14.8 cm.

[0008] Preferably, the optical transmission spectrum range is 0.40 to 0.44 GHz.

[0009] Preferably, the photonic crystal is made of a material with gyromagnetic properties.

[0010] Preferably, the photonic crystal is made of yttrium garnet.

[0011] On the other hand, the present invention provides a light angle sensing method, the method comprising the following steps:

[0012] (1) Based on a one-dimensional double-layer photonic crystal cell, the spacing between scatterers in the upper and lower layers is changed to generate two structural units: Type I with near upper layer and far lower layer and Type II with far upper layer and near lower layer.

[0013] (2) Adjust the spacing between the scatterers to make the bands of the two structures the same, and then take n cells from each of the two structures and splice them together to form a parallel plate waveguide, forming a topological interface in the middle.

[0014] (3) Calculate the waveguide energy state number, find the band gap with two boundary states, calculate the transmission spectrum, and form two Fano curves;

[0015] (4) Change the light incident angle and calculate the relationship between the total extinction ratio and the incident angle of the two Fano curves. Use the above change curve to realize the light angle sensing.

[0016] Preferably, the above-mentioned light angle sensing method includes the following steps:

[0017] (1) Based on a one-dimensional double-layer photonic crystal parallel plate waveguide, each four scatterers form a unit cell. The scatterers in the cell are divided into upper and lower layers, with two scatterers in each layer. The vertical distance between the two layers of scatterers remains unchanged. By changing the spacing between the upper layer scatterers and the spacing between the lower layer scatterers, two different types of basic structural units are generated: Type I (upper near, lower far) and Type II (upper far, lower near).

[0018] (2) Apply a magnetic field to the scatterers of Type I and Type II structures, and adjust the spacing between the scatterers in the upper and lower layers of the Type I and Type II photonic crystals so that the spacing between the two scatterers in the upper layer of the Type I cell is equal to the spacing between the two scatterers in the lower layer of the Type II cell, and the spacing between the two scatterers in the upper layer of the Type II cell is equal to the spacing between the two scatterers in the lower layer of the Type I cell. Then, splice n Type I cells and n Type II cells left and right to form a parallel plate waveguide, and form a topological interface in the middle of the waveguide.

[0019] (3) Calculate the number of energy states of the parallel plate waveguide obtained in step (2), find the boundary state located in the band gap, then perform normal incident light on the parallel plate waveguide, calculate the transmission spectrum of the band gap where the boundary state is located, and obtain two Fano curves generated by the boundary state in the transmission spectrum.

[0020] (4) Change the incident angle of the light on the parallel plate waveguide obtained in step (2), calculate the relationship between the incident angle and the total extinction ratio, and plot the curve of the relationship.

[0021] As a further improvement to the above scheme, step (4) includes changing the angle of the incident light. Starting from normal incidence, the angle of the incident light is slowly deflected clockwise or counterclockwise. The transmission spectrum within the bandgap range described in step (3) is calculated in small step sizes, and the extinction ratio R of the Fano curves at the left and right ends in each transmission spectrum is calculated. ER左 With R ER右 The total extinction ratio R is obtained by adding the extinction ratios of the two locations. ER总 Plot the total extinction ratio R with the incident angle of the light as the independent variable. ER总 The curve showing the relationship between the incident angle of light and the curve.

[0022] The Fano resonance is a widespread wave scattering phenomenon, manifested in the optical transmission spectrum as a Fano curve with sharp asymmetry. The Fano curve has a narrower spectral line shape, which can improve sensing resolution. Compared to the symmetrical Lorentz curve formed by the traditional Lorentz resonance, it has higher sensitivity and a higher extinction ratio R0. ER The absolute value of the ratio of minimum to maximum transmittance is often more than twice that of the Lorentz curve, thus giving the Fano curve a greater advantage in optical sensors. Applying the Fano curve to light angle sensors can significantly improve the sensitivity of light angle sensing. A parallel-plate waveguide topology designed based on a one-dimensional double-layer YIG photonic crystal utilizes the topological boundary states formed in the photonic crystal bandgap to generate a Fano curve in the transmission spectrum. This design not only features a simple structure but also retains the high-sensitivity characteristics of the Fano curve, making it possible to achieve highly sensitive sensing of minute angle deflections of light.

[0023] This invention explores the high-sensitivity light angle sensing characteristics of one-dimensional bilayer YIG photonic crystal topological boundary states. The study found that by using YIG as a scatterer and splicing two different topological state cell structures to form a parallel plate waveguide, two topological boundary states are generated in the bandgap, producing two Fano curves in the transmission spectrum. Subsequently, by slowly increasing the incident light angle from normal incidence, the absolute values ​​of the extinction ratios of the two Fano curves decrease rapidly, and the curve shape gradually changes to a Lorentz shape. The extinction ratios of the two Fano curves are summed to obtain the total extinction ratio, and a curve showing the relationship between the total extinction ratio and the incident angle is plotted. By calculating the slope of the curve, it is found that when the incident angle is less than 0.1°, the rate of change of the absolute value of the total extinction ratio is greater than 486 dB / °, and when the incident angle is less than 1°, the rate of change of the total extinction ratio also exceeds 48 dB / °. This verifies that the system has extremely high sensing sensitivity within a small angular deflection range of the light.

[0024] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: it utilizes the highly sensitive characteristics of Fano curves to achieve small-angle light deflection sensing, and the method uses the total extinction ratio change value of dual Fano curves, which doubles the sensitivity compared to a single Fano curve. This invention enriches the research on topological boundary states and provides a simpler method for achieving high-sensitivity light angle sensing. The research results of this invention will provide guidance for the design of optical devices such as light angle sensors and solar trackers. Attached Figure Description

[0025] Figure 1 The image shows a one-dimensional photonic crystal with four YIG scatterers arranged periodically in the horizontal direction as unit cells and its partial band structure. It contains three different basic structural units: (a) Type I: near-top, far-bottom (d2 / d1>1); (b) scatterers in the upper and lower layers are equally spaced (d5 / d6=1); (c) Type II: far-top, near-bottom (d4 / d3<1). The three unit cells have the same lattice constant a and the same upper and lower plate spacing h, and the interlayer spacing between the upper and lower layers remains unchanged. (d) Partial band structure of Type I structure; (e) Band structure corresponding to scatterers in the upper and lower layers being equally spaced; (f) Partial band structure of Type II structure.

[0026] Figure 2 Figure 1 shows the parallel plate waveguide, energy state number, and boundary state electric field distribution: (a) Schematic diagram of a parallel plate waveguide formed by splicing 4 Type I cells and 4 Type II cells side-by-side, with a lattice constant a = 22 cm; (b) Energy state number diagram (k) corresponding to the parallel plate waveguide in Figure (a). x =0), the shaded area in the figure is the corresponding band gap range in the energy band, and A and B in the figure are two boundary states formed in the band gap near 0.4 GHz; (c) the electric field distribution at the two boundary states A and B marked in Figure (b).

[0027] Figure 3 Figure 1 shows the normal incident transmission spectrum of a parallel plate waveguide and the electric field distribution at the transmission peaks: (a) The transmission spectrum is plotted when light is normally incident from the left port of the parallel plate waveguide. Two Fano curves are seen in the transmission spectrum, with A and B representing the transmission peaks of the left and right Fano curves, respectively; (b) The electric field distribution at the two Fano peaks A (f = 0.40996 GHz) and B (f = 0.42540 GHz) in Figure (a).

[0028] Figure 4 Transmission spectra of light incident from the left port of the parallel plate waveguide at different angles: (a) Transmission spectrum when light is incident normally (incident angle 0°), with the extinction ratio R of the left Fano curve. ER左 = -108.06dB, extinction ratio R of the dextrofan curve ER右= -87.82dB, C and D represent the transmission valleys of the two Fano curves respectively; (b) Transmission spectrum when the incident angle is 2°, extinction ratio R of the left Fano curve ER左 = -66.55dB, extinction ratio R of dextrofano curve ER右 = -68.86dB; (c) Transmission spectrum at an incident angle of 5°, extinction ratio R of the left Fano curve ER左 = -58.79dB, extinction ratio R of the dextrofan curve ER右 = -61.05dB; (d) Transmission spectrum at an incident angle of 10°, extinction ratio R of the left Fano curve ER左 = -53.41dB, extinction ratio R of the dextrofan curve ER右 = -55.27dB; (e) Transmission spectrum at an incident angle of 15°, extinction ratio R of the left Fano curve ER左 = -50.92dB, extinction ratio R of the dextrofan curve ER右 = -52.12dB; (f) Transmission spectrum when the incident angle of light is 30°. At this time, the curve has basically lost the sharp asymmetry of the Fano curve and gradually becomes a Lorentz curve.

[0029] Figure 5 A comparison of the electric field distribution at different incident angles and the relationship between the total extinction ratio and the incident angle: (a) Figure 4 (a) shows the electric field distribution at the transmission valleys C and D of the two Fano curves on the left half of the parallel plate waveguide, with an incident angle of 0°, a frequency of 0.40860 GHz at C, and a frequency of 0.42732 GHz at D; (b) shows the electric field distribution at two locations with the same frequency as in Figure (a) in the transmission spectrum when the incident angle is 30°, also on the left half of the parallel plate waveguide; (c) shows the relationship between the total extinction ratio of the two Fano curves as the incident angle changes from 0° to 20° (the deflection is clockwise or counterclockwise, and the two cases are exactly the same). Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0031] This invention provides a light angle sensor, comprising a parallel plate waveguide with a topological structure. The parallel plate waveguide consists of a parallel plate waveguide and a magnetic field applied to it. The parallel plate waveguide is constructed from a one-dimensional double-layer photonic crystal. The one-dimensional double-layer photonic crystal is formed by combining four sequentially distributed Type I cells and four sequentially distributed Type II cells side-by-side. The Type I cells have the same structure as the Type II cells after rotating 180° around their geometric center. The magnetic field is applied perpendicular to the plane of the scatterer structure to change the permeability of the one-dimensional double-layer photonic crystal to a gyromagnetic form. Both types of cells have identical band structures. The four Type I cells and four Type II cells are combined side-by-side to form the parallel plate waveguide with the topological structure.

[0032] In this embodiment, each unit cell in the one-dimensional bilayer photonic crystal consists of four scatterers. The scatterers within the cell are divided into upper and lower layers, with two scatterers in each layer, and the vertical distance between the two layers of scatterers is equal. For Type I cells, the distance between the two scatterers in the upper layer is smaller than the distance between the two scatterers in the lower layer. For Type II cells, the distance between the two scatterers in the upper layer is greater than the distance between the two scatterers in the lower layer. The lattice constant of the parallel plate waveguide is a = 22 cm, the width between the upper and lower hard boundaries of the waveguide is h = 29.6 cm, the spacing between the scatterers in the upper layer of the Type I cell is d1 = 6.6 cm, and the spacing between the scatterers in the lower layer is d2 = 15.4 cm. For Type II cells, the spacing between the scatterers in the upper layer is d3 = 15.4 cm, and the spacing between the scatterers in the lower layer is d4 = 6.6 cm. The radius of the scatterers in the unit cell is 2.67 cm, and the vertical distance between the horizontal center lines of the upper and lower layers of scatterers is fixed at 14.8 cm. The optical transmission spectrum ranges from 0.40 to 0.44 GHz.

[0033] This invention provides a method for achieving highly sensitive light angle sensing using the aforementioned light angle sensor, comprising the following steps:

[0034] Step 1: A one-dimensional YIG photonic crystal parallel plate waveguide based on two-layer scatterers is constructed. Each unit cell consists of four scatterers, and the scatterers within the cell are divided into upper and lower layers, with two scatterers in each layer. The vertical distance between the two layers of scatterers is constant. By changing the spacing between the upper and lower scatterers, the following effects are generated:

[0035] Type I (near-top, far-bottom): The distance between the two scatterers in the upper layer of the cell is smaller than the distance between the two scatterers in the lower layer.

[0036] Type II (top-far, bottom-near): The distance between the two scatterers in the upper layer of the cell is greater than the distance between the two scatterers in the lower layer.

[0037] Two basic structural units with different topological states;

[0038] Step 2: Apply a magnetic field perpendicular to the structural plane at all YIG scatterers to change the permeability of the YIG material to a gyromagnetic form. Then adjust the spacing between the scatterers in the upper and lower layers of the Type I and Type II photonic crystals so that the spacing between the two scatterers in the upper layer of a Type I cell is equal to the spacing between the two scatterers in the lower layer of a Type II cell, and the spacing between the two scatterers in the upper layer of a Type II cell is equal to the spacing between the two scatterers in the lower layer of a Type I cell. At this point, the Type II cell can coincide with the Type I cell after rotating 180° around its geometric center. The two types of photonic crystals have identical band structures. Then, combine four Type I photonic crystal cells and four Type II photonic crystal cells side by side to form a parallel plate waveguide. The structures on the left and right sides are in different topological states, but the band structures are the same, thus forming topological boundary states in the same band gap.

[0039] Step 3: To further explore the bandgap range in which the boundary states of the parallel plate waveguide obtained in Step 2 reside, the number of energy states of the parallel plate waveguide obtained in Step 2 was calculated. It was found that there are two topological boundary states in the bandgap range near 0.4 GHz. The transmission spectrum of this bandgap was calculated, and two positive and negative Fano curves were found to form at the frequencies corresponding to the two boundary states. The extinction ratios of the two Fano curves were calculated to be R0 and R1 respectively. ER左 With R ER右 .

[0040] Step 4: Change the angle of the incident light. Starting from normal incidence (0°), slowly deflect the angle of the incident light clockwise (or counterclockwise), calculating the transmission spectrum within the bandgap range described in Step 3 in small step sizes. Also, calculate the extinction ratio R of the Fano curves at the left and right points in each transmission spectrum. ER左 With R ER右 The total extinction ratio R is obtained by adding the extinction ratios of the two locations. ER总 Plot the total extinction ratio R with the angle of incidence of light as the independent variable. ER总 The relationship curves with the change of light incident angle show that as the incident angle gradually increases, the absolute value of the extinction ratio of the two Fano curves will continuously decrease, and the line shape of the Fano curves will gradually change to the Lorentz line shape. Furthermore, the slope of the tangent of the relationship curves is extremely large in the range where the incident angle is close to 0°. This proves that the double Fano curves formed by the topological boundary states of YIG photonic crystal can achieve high-sensitivity sensing of small angle deflections of light.

[0041] This invention provides a method for light angle sensing using topological boundary states of a one-dimensional double-layer YIG photonic crystal. A topological interface is formed in a parallel-plate waveguide of the YIG photonic crystal using two different topological state structures. A magnetic field is applied at the scatterer to change the permeability of the YIG to a gyromagnetic form. The energy state number of the waveguide is then calculated to find the band gap where the boundary states exist. The transmission spectrum is then calculated within the corresponding band gap frequency range. The lattice constant is adjusted to form a double Fano curve in the transmission spectrum between the two boundary states. Finally, the angle of incident light is slowly changed, and the change in the extinction ratio of the Fano curve is calculated to obtain the relationship between the total extinction ratio of the double Fano curve and the incident angle. The relationship curve between the total extinction ratio and the incident angle is plotted, revealing that the parallel-plate waveguide has very high sensitivity to small changes in the incident angle. Specific embodiments are as follows:

[0042] Three structures of one-dimensional bilayer YIG photonic crystals, as follows Figure 1 As shown, the two different topological states in the YIG photonic crystal parallel plate waveguide are formed by... Figure 1 (b) is a variation of the structure of the equally spaced YIG scatterers. Its basic structure consists of YIG cylinders placed against an air background as scatterers, with ideal electrical conductors used for the upper and lower hard boundaries, and four YIG scatterers forming a single cell. As a material with gyromagnetic properties, YIG's permeability changes to a new gyromagnetic form under an applied magnetic field, which can be represented by a matrix:

[0043]

[0044] (1) In the formula, Let represent the permeability matrix. With an applied magnetic field of 1600 Gauss, μ = 14μ0, κ = 12.4μ0, i is the imaginary unit, and μ0 is the permeability of free space.

[0045] The lattice constant is set to a = 22 cm, the vertical width is h = 29.6 cm, the radius of the YIG scatterer is 2.67 cm, the vertical distance between the horizontal center lines of the upper and lower layers of scatterers within the cell is 14.8 cm, the dielectric constant is ε = 15ε0, where ε0 is the vacuum dielectric constant, and the permeability is the gyromagnetic matrix in equation (1). Next, two different topological structures, Type I and Type II, are formed by adjusting the center-to-center distance within the upper and lower layers. For example... Figure 1 (b) and Figure 1 As shown in (e), when the spacing between all scatterers in the upper and lower layers is equal, the energy band near 0.4 GHz is closed, at which point d5 = d6 = 11 cm; then the center-to-center distance of the scatterers in the upper layer is shortened, and the center-to-center distance of the scatterers in the lower layer is increased to... Figure 1 In the structure shown in (a), it was found that the energy bands would open to form a band gap (e.g., ...). Figure 1 (as shown in (d)); further increase the center distance of the upper inner scattering particles and shorten the center distance of the lower inner scattering particles to... Figure 1In the structure shown in (c), the bands reopen, forming a band gap (as in...). Figure 1 (f) As shown, by adjusting the distance between the centers of the inner scatterers in the upper and lower layers, the Type II structure can be completely superimposed on the Type I structure after rotating 180° around its geometric center. At this time, the two different topological states have the same band structure. The change from Type I to the equal spacing between the inner scatterers in the upper and lower layers and then to Type II can be regarded as the process of the band going from open to closed and then open again, that is, the band has been flipped. Therefore, the two structures are in different topological phases.

[0046] Take four cells from each of Type I and Type II, and splice them together to form a structure like... Figure 2 As shown in (a), a parallel plate waveguide forms a topological interface in the middle. Then, the energy state number of the parallel plate waveguide structure is calculated, such as... Figure 2 As shown in (b), the shaded area represents the bandgap frequency range, while the rest is the passband. Two topological boundary states, A and B, appear in the bandgap near 0.4 GHz. Calculate the electric field distribution at A and B (e.g., ...). Figure 2 As shown in (c), it was found that two different boundary states were indeed formed at the topological boundary. Below, a frequency range containing these boundary states (A and B) is selected near them for optical transmission spectrum calculation. Figure 3 As shown in (a), light is incident normally from the left port of the parallel plate waveguide. A transmission spectrum range of 0.40–0.44 GHz is selected, and two Fano curves are observed. The frequencies corresponding to the peaks of these two curves are consistent with the frequencies of the two boundary states calculated previously. The transmission electric field distribution at the two Fano peaks is then calculated, and it corresponds one-to-one with the electric field distributions at boundary states A and B. This verifies that the two Fano curves are formed by the two topological boundary states respectively. Next, the angle of light incidence is slowly changed (clockwise or counterclockwise deflection), and the changes in the double Fano curves as the incident angle increases are recorded. Figure 4 The extinction ratio and line shape of the two Fano curves were recorded for light incident angles of 0°, 2°, 5°, 10°, 15°, and 30°. It can be seen that the absolute value of the extinction ratio of both Fano curves gradually decreases with increasing incident angle, and the rate of change is larger at smaller incident angles. The line shape of the Fano curve also gradually changes to a Lorentz shape. Since the extinction ratios of the two Fano curves show the same trend, they can be added together to obtain the total extinction ratio. Calculating the relationship between the total extinction ratio and the incident angle can further improve the sensitivity of the angle sensor. Figure 4 The changing trend of the Fano curve reveals that the main changes in the line shape occur at the valleys of the Fano curve as the incident angle changes. Therefore, to investigate the influence of the incident angle on the extinction ratio of the Fano curve, the transmission electric field distribution on the left half of the waveguide at the two valleys of the curve when the incident angle is 0° is calculated (e.g., Figure 5(a) shows the transmission electric field distribution on the left half of the waveguide at the same frequency as the curve at an incident angle of 30° (as shown in (a)). Figure 5 As shown in (b), by comparison, it can be seen that the larger the incident angle, the more the electric field will be distributed in the background air, and the electric field distribution is less affected by scatterers; although the propagation of the electric field does not change much, it is enough to cause a large fluctuation in the extinction ratio for the valley of the Fano curve, which has very low transmittance and is very sensitive.

[0047] Finally, to obtain a more accurate relationship between the total extinction ratio and the incident angle, starting from normal incidence (incident angle = 0°), the angle of the incident light is slowly deflected clockwise (or counterclockwise), and the transmission spectrum corresponding to each angle is calculated in small angles (0.1°). The extinction ratio R of the two Fano curves on the left and right sides of each transmission spectrum is then calculated. ER左 With R ER右 The two extinction ratios are then added together to obtain the total extinction ratio R. ER总 Plot the total extinction ratio R with the incident angle of the light as the independent variable. ER总 The relationship curve between light incident angle and other parameters (e.g.) Figure 5 (c) As shown in the curve, it can be seen from the relationship curve that the rate of change of the curve is extremely large when the incident angle of light is near 0°. By calculating the slope of the tangent of the curve, it was found that when the incident angle is less than 0.1°, the rate of change of the absolute value of the total extinction ratio is greater than 486dB / °, and when the incident angle is less than 1°, the rate of change of the absolute value of the total extinction ratio also exceeds 48dB / °. This verifies that the system has extremely high sensing sensitivity within a small range of light angle changes.

[0048] In summary, this invention provides a method for sensing light angle. Based on a one-dimensional double-layer YIG photonic crystal four-scatterer cell structure, this invention achieves two different topological states by adjusting the spacing between scatterers in the upper and lower layers of the cell. These two topological states are then spliced ​​together to form a topological interface, generating two topological boundary states. By calculating the transmission spectrum, it is found that the topological boundary states form double Fano curves. Furthermore, by deflecting the light incident angle, the relationship between the total extinction ratio of the two Fano curves and the light incident angle is obtained. Since the Fano curves have high sensing sensitivity, and this invention utilizes the sum of the extinction ratios of the two Fano curves as the sensing dependent variable, the waveguide's sensitivity to light angle sensing is further improved. This is a simple method for realizing light angle sensing and also provides a reference for the research and application of topological boundary states.

[0049] The above description is merely a detailed explanation of the present invention in conjunction with specific technical solutions, and should not be construed as limiting the specific implementation of the present invention to the above description. For those skilled in the art, any modifications or equivalent substitutions made to the technical solutions of the present invention without departing from the spirit and scope of the present invention are all covered within the protection scope of the present invention.

Claims

1. A light angle sensor, characterized in that, The light angle sensor includes a parallel plate waveguide with a topological structure. The parallel plate waveguide with the topological structure is composed of a parallel plate waveguide and a magnetic field applied to the parallel plate waveguide. Under the action of the magnetic field, two topological boundary states are generated in the band gap of the parallel plate waveguide. The parallel plate waveguide is composed of a one-dimensional double-layer photonic crystal. The one-dimensional double-layer photonic crystal is composed of n sequentially distributed Type I cells and n sequentially distributed Type II cells spliced ​​together from left to right. The structure of the Type I cell is the same as that of the Type II cell after rotating it 180° around its geometric center. The magnetic field is applied perpendicular to the plane of the scatterer structure to change the permeability of the one-dimensional bilayer photonic crystal into a gyromagnetic form. The two types of cells have the same band structure. n Type I cells and n Type II cells are spliced ​​together to form a parallel plate waveguide with a topological structure. In the one-dimensional bilayer photonic crystal, each unit cell consists of four scatterers. The scatterers within the cell are divided into upper and lower layers, with two scatterers in each layer. The vertical distance between the two layers of scatterers remains constant. The Type I cell is characterized by a smaller distance between the two scatterers in the upper layer than between the two scatterers in the lower layer. The Type II cell is characterized by a larger distance between the two scatterers in the upper layer than between the two scatterers in the lower layer.

2. The light angle sensor according to claim 1, characterized in that, The parallel plate waveguide has a cell lattice constant a = 22 cm, a width h = 29.6 cm between the upper and lower hard boundaries, an upper layer scatterer spacing d1 = 6.6 cm, a lower layer scatterer spacing d2 = 15.4 cm, an upper layer scatterer spacing d3 = 15.4 cm, and a lower layer scatterer spacing d4 = 6.6 cm in the Type I cell.

3. The light angle sensor according to claim 1, characterized in that, The radius of the scatterer in the unit cell is 2.67 cm, and the vertical distance between the horizontal center lines of the upper and lower layers of scatterers is fixed at 14.8 cm.

4. The light ray angle sensor of claim 1, wherein, The optical transmission spectrum ranges from 0.40 to 0.44 GHz.

5. The light angle sensor according to claim 1, characterized in that, The photonic crystal is made of a material with gyromagnetic properties.

6. The light angle sensor according to claim 1, characterized in that, The photonic crystal is made of yttrium garnet.

7. A light ray angle sensing method, characterized by, The method includes the following steps: (1) Based on the cell of a one-dimensional double-layer photonic crystal, the spacing between the scatterers in the upper and lower layers is changed to generate two types of structural units: Type I (near-upper, far-lower) and Type II (far-upper, near-lower). Type I (near-upper, far-lower) is: the spacing between the two scatterers in the upper layer of the cell is smaller than the spacing between the two scatterers in the lower layer. Type II (far-upper, near-lower) is: the spacing between the two scatterers in the upper layer of the cell is greater than the spacing between the two scatterers in the lower layer. Based on the parallel plate waveguide of the one-dimensional double-layer photonic crystal, each four scatterers form a unit cell. The scatterers in the cell are divided into upper and lower layers, with two scatterers in each layer. The vertical distance between the two layers of scatterers remains unchanged. By changing the spacing between the upper scatterers and the spacing between the lower scatterers, two different types of basic structural units are generated: Type I (near-upper, far-lower) and Type II (far-upper, near-lower). (2) Adjust the spacing between the scatterers to make the bands of the two structures the same, and then take n cells from each of the two structures and splice them together to form a parallel plate waveguide, forming a topological interface in the middle; wherein, apply a magnetic field to the scatterers of the Type I and Type II structures, and adjust the spacing between the scatterers in the upper and lower layers of the Type I and Type II photonic crystals so that the spacing between the two scatterers in the upper layer of the Type I cell is equal to the spacing between the two scatterers in the lower layer of the Type II cell, and the spacing between the two scatterers in the upper layer of the Type II cell is equal to the spacing between the two scatterers in the lower layer of the Type I cell. Then splice n Type I cells and n Type II cells together to form a parallel plate waveguide, forming a topological interface in the middle of the waveguide; (3) Calculate the waveguide energy state number, find the band gap with two boundary states, calculate the transmission spectrum, and form two Fano curves; (4) Change the light incident angle and calculate the relationship between the total extinction ratio and the incident angle of the two Fano curves. Use the above relationship curve to realize the light angle sensing.

8. The light ray angle sensing method according to claim 7, wherein, Step (4) involves changing the angle of the incident light. Starting from normal incidence, the angle of the incident light is slowly deflected clockwise or counterclockwise. The transmission spectrum within the band gap range described in step (3) is calculated in small step sizes, and the extinction ratio of the Fano curves at the left and right ends of each transmission spectrum is calculated. R ER左 and R ER右 The total extinction ratio is obtained by adding the extinction ratios of the two locations. R ER总 Using the angle of incidence of light as the independent variable, plot the total extinction ratio. R ER总 The curve showing the relationship between the incident angle of light and the curve.

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