Fano resonance based sensor and method of detection of mixed solutions

Abstract

The present disclosure provides a sensor based on Fano resonance and a mixed solution detection method, the sensor comprising a waveguide structure; the waveguide structure comprises a strip waveguide and a plurality of ring waveguides coupled with the strip waveguide; the strip waveguide is provided with a plurality of reflection units; the strip waveguide is used for receiving incident light; the reflection units are used for reflecting the incident light to form reflected light in a discrete state; the ring waveguides are used for circulating propagation of the incident light in the ring waveguides to form transmitted light in a continuous state; wherein the reflected light and the transmitted light interfere with each other to produce Fano resonance. The present disclosure sets a plurality of reflection units in the strip waveguide to form reflected light in a discrete state, thereby being able to produce Fano resonance, realizing detection of mixed solutions without using a functionalized cavity array, improving detection efficiency and detection accuracy, reducing detection difficulty, and expanding application range; the device size is relatively small, greatly improving the integration, and having a broad application prospect.

Description

Technical Field

[0001] This disclosure relates to the field of optical device technology, and in particular to a sensor based on Fano resonance and a method for detecting mixed solutions. Background Technology

[0002] A microring resonator is a miniature resonant structure based on an optical waveguide. It utilizes the cyclic interference of light to create resonance and is widely used in integrated photonics, optical communication, and biosensing. Light enters from a straight waveguide, couples through an evanescent field into the microring, and propagates cyclically within the ring. Resonance occurs when the phase change of the light during one revolution within the ring is an integer multiple of 2π. At resonance, the light is amplified within the ring, resulting in a Lorentz line shape in the transmission spectrum of the straight waveguide. While the Lorentz line shape is widely used due to its simplicity, it has limitations in applications such as high-sensitivity sensing, detection of complex media, and multi-parameter analysis.

[0003] The Fano resonance originates from the interference between a narrow-linewidth discrete state and a broad-spectrum continuous state, and its asymmetric line shape is extremely sensitive to changes in the surrounding environment. This unique resonance characteristic can significantly enhance the detection sensitivity of the sensor, making it particularly suitable for detecting trace molecules or weak physical quantities. The sharp asymmetric peak of the Fano resonance can effectively suppress background noise and improve signal contrast, thereby enhancing the sensor's signal-to-noise ratio and enabling it to maintain high-precision detection even in complex environments. Its high sensitivity allows for the detection of extremely low concentrations of analytes (such as at the single-molecule level), making it of significant application value in fields such as biomedical detection and environmental monitoring.

[0004] Traditional waveguide sensors (such as Mach-Zehnder interferometers and microring resonators) detect analytes by phase / wavelength changes. They typically strive to minimize losses to improve the sensitivity of real refractive index detection, but can only provide indirect information about the concentration or composition of the analyte and cannot fully characterize the material properties. Summary of the Invention

[0005] The technical problem to be solved by this disclosure is to overcome the shortcomings of existing waveguide sensors that detect analytes by phase / wavelength changes, which cannot fully characterize the properties of materials, and to provide a sensor based on Fano resonance and a detection method for mixed solutions.

[0006] This disclosure solves the above-mentioned technical problems through the following technical solution:

[0007] This disclosure provides a sensor based on Fano resonance, the sensor including a waveguide structure;

[0008] The waveguide structure includes a strip waveguide and several ring waveguides coupled to the strip waveguide;

[0009] The strip waveguide is provided with several reflection units;

[0010] The strip waveguide is used to receive incident light;

[0011] The reflecting unit is used to reflect the incident light to form discrete reflected light;

[0012] The ring waveguide is used to allow the incident light to propagate cyclically within the ring waveguide, forming a continuous state of transmitted light;

[0013] The reflected light and the transmitted light interfere with each other to produce the Fano resonance.

[0014] Optionally, the sensor is used to detect the concentration of each component in the mixed solution;

[0015] The concentration is obtained based on the real and / or imaginary refractive indices of the mixed solution;

[0016] The real refractive index is obtained based on the wavelength of the resonance peak of the Fano resonance generated by the mixed solution;

[0017] The imaginary refractive index is obtained based on the intensity of the resonance peak of the Fano resonance generated by the mixed solution.

[0018] Optionally, the number of the reflective units is odd.

[0019] Optionally, the number of reflective units is three.

[0020] Optionally, the spacing between two adjacent reflective units is 500 nm;

[0021] And / or,

[0022] The first center of the reflecting unit, which is located in the middle position, and the second center of the ring waveguide are on the same straight line, and the straight line is perpendicular to the length direction of the strip waveguide.

[0023] Optionally, there are two annular waveguides, which are disposed on both sides of the strip waveguide.

[0024] Optionally, the coupling gap between each of the ring waveguides and the strip waveguides is the same.

[0025] Optionally, the coupling gap is 200 nm.

[0026] Optionally, the waveguide structure is made of a chalcogenide material;

[0027] And / or,

[0028] The height of the waveguide structure is 300 nm;

[0029] And / or,

[0030] The width of the waveguide structure is 600 nm;

[0031] And / or,

[0032] The radius of the reflective unit is 200 nm;

[0033] And / or,

[0034] The sensor also includes a substrate layer disposed below the waveguide structure;

[0035] And / or,

[0036] The sensor also includes a cladding that surrounds the waveguide structure.

[0037] This disclosure also provides a method for detecting a mixed solution, the method comprising:

[0038] Using the Fano resonance-based sensor as described above, the peak information of the resonance peak of the Fano resonance generated by the mixed solution is obtained, and the peak information includes wavelength and / or intensity;

[0039] Obtain the refractive index of the mixed solution corresponding to the peak information, wherein the refractive index includes the real refractive index and / or the imaginary refractive index;

[0040] Based on the refractive index, the concentrations of each component in the mixed solution are obtained.

[0041] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of this disclosure.

[0042] The positive and progressive effects of this disclosure are as follows:

[0043] This disclosure achieves the detection of mixed solutions by setting several reflective units in a strip waveguide to form discrete reflected light, thereby generating Fano resonance. This overcomes the shortcomings of existing waveguide sensors that detect analytes through phase / wavelength changes, which cannot fully characterize the properties of the material. It realizes the detection of mixed solutions without the need for functionalized cavity arrays, improving detection efficiency and accuracy, reducing detection difficulty, and expanding the application range. The device is also small in size, greatly improving integration and showing broad application prospects. Attached Figure Description

[0044] Figure 1 This is a planar schematic diagram of the waveguide structure of the sensor according to an embodiment of this disclosure;

[0045] Figure 2 This is a schematic diagram of the transmission spectrum of the sensor in the 1520nm-1600nm band according to an embodiment of this disclosure;

[0046] Figure 3 This is a schematic diagram of the transmission spectrum of the sensor according to an embodiment of the present disclosure at different real refractive indices;

[0047] Figure 4 This is a fitting graph of the sensitivity of the real refractive index of the sensor according to an embodiment of this disclosure;

[0048] Figure 5 This is a schematic diagram of the transmission spectrum of the sensor according to an embodiment of the present disclosure at different imaginary refractive indices;

[0049] Figure 6 This is a fitting graph of the sensitivity of the imaginary refractive index of the sensor according to an embodiment of this disclosure;

[0050] Figure 7 The transmission spectra are shown in the comparison diagrams when the number of reflective units in the sensor of the present disclosure is 1, 3, and 5 respectively.

[0051] Figure 8 This is a schematic diagram showing the spacing between reflective units in a sensor according to an embodiment of this disclosure;

[0052] Figure 9 The transmission spectrum comparison diagrams are shown for the spacing L between the reflective units in the sensor of the present disclosure embodiment when they are 500nm, 550nm, and 600nm respectively.

[0053] Figure 10 A comparison of the transmission spectra of sensors containing a single ring and sensors containing a double ring according to embodiments of this disclosure;

[0054] Figure 11 This is a comparison of the transmission spectra of the sensor in this embodiment when the radius r of the reflective unit is 100nm, 150nm, and 200nm, respectively.

[0055] Figure 12 This is a three-dimensional schematic diagram of the sensor according to an embodiment of the present disclosure;

[0056] Figure 13 This is a flowchart of a method for detecting a mixed solution according to an embodiment of the present disclosure. Detailed Implementation

[0057] The present disclosure is further illustrated below by way of embodiments, but the present disclosure is not limited to the scope of the embodiments described herein.

[0058] The prefixes such as "first" and "second" used in this disclosure are merely for distinguishing different descriptive objects and do not limit the position, order, priority, quantity, or content of the described objects. The use of ordinal numbers and other prefixes used to distinguish descriptive objects in this disclosure does not constitute a limitation on the described objects. The description of the described objects is given in the context of the embodiments, and the use of such prefixes should not constitute unnecessary restrictions. Furthermore, in the description of this embodiment, unless otherwise stated, "multiple" means two or more.

[0059] Example 1

[0060] This embodiment provides a sensor based on Fano resonance, which includes a waveguide structure;

[0061] like Figure 1 As shown, the waveguide structure 1 includes a strip waveguide 11 and several ring waveguides 12 coupled to the strip waveguide 11;

[0062] The strip waveguide 11 is provided with a number of reflection units 111;

[0063] Strip waveguide 11 is used to receive incident light;

[0064] The reflecting unit 111 is used to reflect the incident light to form discrete reflected light;

[0065] The ring waveguide 12 is used to allow incident light to propagate cyclically within the ring waveguide 12, forming a continuous state of transmitted light;

[0066] In this process, the reflected light and the transmitted light interfere with each other, producing Fano resonance.

[0067] Specifically, the strip waveguide is linear and has several reflecting elements, which can be circular or elliptical. The ring waveguide includes, for example, a first micro-ring waveguide and a second micro-ring waveguide. The strip waveguide and the ring waveguide are located in the same plane. The strip waveguide with reflecting elements is used to form discrete-state reflected light, and the ring waveguide is used to form continuous-state transmitted light. The two interfere with each other, producing an asymmetric Fano resonance peak.

[0068] The reflective elements in a strip waveguide cause incident light to be reflected, inducing a phase change and thus generating an asymmetric Fano resonance. The reflective elements in the strip waveguide are key to generating the Fano resonance. The transmission spectrum of the sensor in the 1520nm-1600nm wavelength range is as follows: Figure 2 As shown, Figure 2 The horizontal axis represents wavelength (nm), and the vertical axis represents normalized transmittance. Figure 2The diagram illustrates multiple Fano resonances. The resonance peaks of the Fano resonance can be used to test the real and imaginary refractive indices of a solution, enabling complex refractive index sensing. The Fano resonance peaks exhibit high sensitivity in both the real and imaginary refractive indices, significantly improving the sensor's detection accuracy.

[0069] In this scheme, by setting several reflective units in a strip waveguide to form discrete reflected light, a Fano resonance can be generated. This overcomes the shortcomings of existing waveguide sensors that detect analytes through phase / wavelength changes, which cannot fully characterize the properties of the material. It achieves the detection of mixed solutions without the need for functionalized cavity arrays, improving detection efficiency and accuracy, reducing detection difficulty, and expanding the application range. The device is also small in size, greatly improving integration and showing broad application prospects.

[0070] In one feasible approach, the sensor is used to detect the concentration of each component in the mixed solution;

[0071] The concentration is obtained based on the real and / or imaginary refractive indices of the mixed solution;

[0072] The real refractive index is obtained based on the wavelength of the resonance peak of the Fano resonance generated by the mixed solution;

[0073] The imaginary refractive index is obtained based on the intensity of the resonance peak of the Fano resonance generated by the mixed solution.

[0074] Specifically, the complex refractive index sensor of this scheme can be realized by utilizing the resonance peak of the Fano resonance. The complex refractive index consists of the real refractive index and the imaginary refractive index. The real refractive index of the mixed solution is characterized by the wavelength or phase change of the Fano resonance peak, i.e., wavelength shift; the imaginary refractive index is characterized by the intensity change of the resonance peak. The imaginary refractive index reflects the degree of light absorption.

[0075] The sensitivity of the sensor's real refractive index can be tested. To better compare spectral line changes, the imaginary part of the ambient refractive index is kept constant and set to 0, only the real part is changed. For example... Figure 3 As shown, the horizontal axis represents wavelength in nm, and the vertical axis represents normalized transmittance. When the real refractive index changes sequentially from 1.33, 1.331, 1.332, 1.333, and 1.334 RIU, the resonance peak redshifts. The sensitivity of the real refractive index is obtained by fitting the data. ,like Figure 4 As shown, Figure 4The horizontal axis represents the real part of the refractive index (RIU), and the vertical axis represents the resonance wavelength (nm). Here, λ represents the wavelength position corresponding to the resonance peak of the Fano resonance, Δλ represents the change in the wavelength position corresponding to the resonance peak of the Fano resonance, n represents the real part of the refractive index, Δn represents the change in the real part of the refractive index, and S... n The sensitivity of the real part of the refractive index. Figure 4 5 points near the middle line and Figure 3 The wavelength position of the resonance peak of each spectral line corresponds to the real refractive index. Figure 4 It can clearly reflect that the resonance wavelength of the Fano resonance peak increases with the increase of the real part refractive index. The wavelength shift of the resonance peak and the real part refractive index show a good linear relationship, and the slope of the straight line is the sensitivity of the real part refractive index.

[0076] The sensitivity of the sensor's imaginary refractive index can be tested. To better compare spectral changes, the real part of the ambient refractive index is kept constant at 1.331, and only the imaginary part is changed. Figure 5 As shown, the horizontal axis represents wavelength in nm, and the vertical axis represents normalized transmittance. When the imaginary refractive index ranges from 0 to 2.5 × 10⁻⁶... -4 5×10 -4 7.5×10 -4 As the RIU sequence changes, the peak width of the Fano resonance gradually increases, while the slope of the resonance peak gradually decreases. Figure 5 middle The refractive index is represented by both the real and imaginary parts, with the real part being 1.331 RIU. The formula for calculating the sensitivity of the imaginary refractive index is as follows:

[0077] ;

[0078] ;

[0079] ;

[0080] ;

[0081] ;

[0082] Where V represents the intensity of the resonance peak, i.e., the light intensity contrast; λ peak and λ dip T represents the wavelengths corresponding to the peak and trough values ​​of the Fano resonance, respectively. max and T min They represent respectively at λ peak and λdip Transmittance at wavelength, D(λ) represents peak width, P represents the slope of the Fano resonance peak, F represents the logarithm of P, ΔF represents the change in the logarithm of P, k represents the imaginary refractive index, Δk represents the change in the imaginary refractive index, S k This represents the sensitivity of the real part of the refractive index. P has a curvilinear relationship with k, therefore taking the logarithm of P yields F.

[0083] The fitting plot of the sensitivity of the imaginary refractive index obtained by fitting is shown in the figure. Figure 6 As shown, Figure 6 The horizontal axis represents the imaginary part of the refractive index, expressed in RIU, while the vertical axis represents the logarithm of the slope of the Fano resonance peak. Figure 6 4 points near the middle line and Figure 5 The slope of the resonance peak of each spectral line corresponds to the imaginary refractive index. Figure 6 It can clearly reflect that the logarithm of the slope of the Fano resonance decreases as the imaginary refractive index increases. The logarithm of the slope of the resonance peak and the imaginary refractive index show a good linear relationship, and the slope of the straight line is the sensitivity of the imaginary refractive index.

[0084] The sensitivity of the real part of the refractive index and the sensitivity of the imaginary part of the refractive index can reflect the sensing performance of the sensor. The higher the sensitivity, the more accurate the measurement of the real part and imaginary part of the refractive index of the mixed solution of unknown concentration, and the more accurate the concentration of each component of the mixed solution is obtained.

[0085] By testing the sensor, two mapping relationships can be obtained: a first mapping relationship between the wavelength of the resonance peak and the real refractive index, and a second mapping relationship between the intensity of the resonance peak and the imaginary refractive index. The first mapping relationship is linear. By converting the intensity of the resonance peak in the second mapping relationship, a second mapping relationship between the logarithm of the slope of the Fano resonance peak and the imaginary refractive index can be obtained. The third mapping relationship is also linear.

[0086] For ternary mixtures of unknown concentration, such as a mixture of water, methanol, and acetonitrile, the higher the acetonitrile content, the greater the harm to the human body. To detect the acetonitrile content in such a solution, firstly, the wavelength position and corresponding intensity of the Fano resonance peak are measured. Based on the intensity, the slope of the Fano resonance peak can be obtained, and then the logarithm of the slope can be calculated. Next, the wavelength position and the logarithm of the Fano resonance peak slope are substituted into the first and third linear relationships to obtain the real and imaginary refractive indices of the ternary mixture. Finally, the real and imaginary refractive indices of the ternary mixture are substituted into the formula for the equivalent complex refractive index of the mixture to obtain the concentration of each component. The formula for the equivalent complex refractive index of the mixture is a linear superposition of the equivalent complex refractive index and the complex refractive indices of each component, as shown in the following formula:

[0087] ;

[0088] ;

[0089] Where, n med k represents the real refractive index of the mixed solution. med Let represent the imaginary refractive index of the mixed solution, j represent the exponents of the components in the mixed solution, j ≤ the total number of components in the mixed solution, and c j n represents the concentration of each component. j and k j Let n represent the real and imaginary refractive indices of each component, respectively. j and k j It can be found in existing literature and materials.

[0090] The acetonitrile content can be determined by analyzing the concentration of each component in the ternary mixed solution; based on the acetonitrile content, the degree of harm to the human body from the solution can be assessed.

[0091] This sensor combines the real and imaginary refractive indices, enabling the detection of not only binary but also ternary mixed solutions without the need for functionalized cavity arrays. This improves detection efficiency, reduces detection difficulty, and expands the application range. The sensor is applicable to all ternary mixed solutions; for any ternary mixed solution containing an unknown concentration of toxic components, the sensor can detect the concentration of the toxic components, thereby determining its safety and degree of contamination.

[0092] This solution improves detection efficiency and accuracy, reduces detection difficulty, and expands the application range by fully utilizing the direct and interference-resistant detection capability of the imaginary refractive index.

[0093] In a feasible scheme, the number of reflective units is odd.

[0094] The number of reflection units in a strip waveguide affects the realization of Fano resonance; it should be designed to be an odd number and symmetrically distributed. An even number of reflection units may lead to mode degeneracy, while an odd number of reflection units can break the symmetry, enhance the interference effect, and promote the formation of Fano resonance.

[0095] In this scheme, an odd number of reflection units are set in the strip waveguide, which promotes the formation of Fano resonance and ensures the reliability and effectiveness of the sensor.

[0096] In one feasible scheme, the number of reflective units is 3.

[0097] Specifically, such as Figure 7 As shown, the horizontal axis represents wavelength in nm, and the vertical axis represents normalized transmittance. When there is one reflective unit, the spectral lines are close to the Lorentz line type, indicating a small phase change and insignificant Fano resonance. When there are three reflective units, a significant Fano resonance appears. When there are five reflective units, the incident light loss in the reflective units is significant, and spectral lines appear close to the anti-Lorentz line type. Therefore, the number of reflective units is designed to be three.

[0098] In this scheme, three reflection units are set in the strip waveguide to ensure the formation of Fano resonance, thus guaranteeing the reliability and effectiveness of the sensor.

[0099] In one feasible scheme, the spacing between two adjacent reflective elements is 500 nm;

[0100] Specifically, such as Figure 8 As shown, the spacing L between two reflective elements, i.e., the distance between the centers of the reflective elements, affects the phase change. To meet the fabrication requirements, the spacing between two adjacent reflective elements cannot be less than 500 nm. Figure 9 As shown, the horizontal axis represents wavelength in nm, and the vertical axis represents normalized transmittance. As the spacing L gradually decreases from 600 nm to 550 nm, and finally to 500 nm, the Fano resonance becomes more pronounced, and the extinction ratio increases. However, a spacing L that is too small would affect device fabrication; therefore, L was designed to be 500 nm.

[0101] In this scheme, the spacing between two adjacent reflective units is set to 500 nm, which satisfies the device fabrication conditions, ensures the generation of Fano resonance, increases the extinction ratio of the transmission spectrum, and improves the reliability of the measurement results.

[0102] In one feasible scheme, the first center of the reflective element in the middle position is on the same straight line as the second center of the ring waveguide, and the straight line is perpendicular to the length direction of the strip waveguide.

[0103] Specifically, a Cartesian coordinate system is established with the first center of the reflecting unit located in the middle position as the origin, the length direction of the strip waveguide as the Y-axis, and the direction perpendicular to the length direction of the strip waveguide as the X-axis. In this coordinate system, the Y-axis coordinate y1 of the first center of the reflecting unit located in the middle position of the strip waveguide coincides with the Y-axis coordinate y2 of the second center of the ring waveguide. At this point, the Fano resonance effect is strongest. The greater the difference in the Y-axis coordinates, the less obvious the Fano resonance becomes, and it will gradually become a Lorentzian shape. Therefore, it is necessary to ensure that the Y-axis coordinates are consistent.

[0104] In this scheme, the first center of the reflective unit located in the middle position and the second center of the ring waveguide are on the same straight line. The straight line is perpendicular to the length direction of the strip waveguide, which ensures the generation of Fano resonance and guarantees the reliability and effectiveness of the sensor.

[0105] In one feasible scheme, there are two ring waveguides, which are located on both sides of the strip waveguide.

[0106] Specifically, due to the presence of reflecting elements in the strip waveguide, the extinction ratio of the transmission spectrum is relatively small, and the resonance peak may be submerged by noise. A higher extinction ratio results in a higher contrast between the resonance peak and background noise, leading to more reliable measurement results. To increase the extinction ratio, two ring waveguides are used, i.e., a double-ring design. For example... Figure 10 As shown, the horizontal axis represents wavelength in nm, and the vertical axis represents transmittance in dB. It can be seen that the extinction ratio is significantly increased in the dual-ring design compared to the single-ring design. The single-ring design uses a single ring waveguide. Three or more ring waveguides will exhibit numerous resonance peaks with very low extinction ratios (Fano resonance), which is detrimental to sensor sensitivity testing.

[0107] In this scheme, by designing two ring waveguides, the extinction ratio of the transmission spectrum is increased, thereby improving the reliability of the measurement results.

[0108] In one feasible approach, the coupling gap between each ring waveguide and strip waveguide is the same.

[0109] Specifically, in order to ensure that the Fano resonances do not overlap, the coupling gaps between the two ring waveguides and the straight waveguide must be kept the same.

[0110] In this scheme, by setting the coupling gap between each ring waveguide and strip waveguide to be the same, the Fano resonances are ensured to not overlap, thus improving the reliability of the measurement results.

[0111] In one feasible approach, the coupling gap is 200 nm.

[0112] In this scheme, the coupling gap between each ring waveguide and strip waveguide is set to 200nm, which ensures a high quality factor Q value and extinction ratio, and improves the reliability of the measurement results.

[0113] In one feasible approach, the waveguide structure is made of a chalcogenide material.

[0114] Specifically, chalcogenide materials are chalcogenide glasses (ChGs), such as Ge. 28 Sb 12 Se 60 .

[0115] ChGs are amorphous materials mainly formed by covalent bonds between chalcogenide elements (such as sulfur (S), selenium (Se), and tellurium (Te)) and certain metallic or nonmetallic elements. These materials exhibit excellent light transmittance in the near-infrared band, with sulfides, selenides, and tellurides reaching transmittance wavelengths of 12, 14, and 20 micrometers, respectively, completely covering the key wavelength range of near-infrared sensing.

[0116] Compared to traditional semiconductor materials such as silicon and germanium, chalcogenide glasses exhibit a wider bandgap, resulting in lower two-photon absorption, making them ideal optical materials. Furthermore, unlike crystalline fluorides and semiconductors, chalcogenide glasses can be directly deposited on substrate wafers without considering lattice matching issues, thus facilitating the fabrication of ultrathin films. The fabrication processes for chalcogenide devices are fully compatible with complementary metal-oxide-semiconductor (CMOS) micro / nano fabrication techniques, providing a significant advantage for their applications in integrated optics and optoelectronics.

[0117] In this scheme, a waveguide structure made of chalcogenide materials is used to ensure the effectiveness and reliability of the sensor and improve its optical performance.

[0118] In one feasible scheme, the waveguide structure has a height of 300 nm and a width of 600 nm.

[0119] Specifically, for strip waveguides, their height and width jointly determine the number of modes. When the waveguide height is greater than 300nm, higher-order modes will appear when the waveguide width is greater than 740nm. To satisfy the TE0 fundamental mode single-mode transmission, a waveguide width of 600nm is chosen, and the waveguide height is designed to be 300nm. A waveguide width less than 740nm is the theoretical critical value for satisfying TE0 fundamental mode transmission. In actual manufacturing processes, there are fluctuations and errors. If it is exactly 740nm, higher-order modes may be excited. Choosing 600nm provides a 140nm process tolerance, significantly reducing the multimode risk caused by process fluctuations.

[0120] The height of the reflecting unit is the same as the height of the waveguide structure, both being 300 nm.

[0121] In this scheme, the waveguide structure is set to a height of 300nm and a width of 600nm to meet the requirements of TEO fundamental mode single-mode transmission and the device fabrication process requirements.

[0122] In one feasible approach, the radius of the reflective element is 200 nm.

[0123] Specifically, the radius *r* of the reflecting element affects the reflectivity, thus affecting the phase change. For example... Figure 11 As shown, the horizontal axis represents wavelength in nm, and the vertical axis represents normalized transmittance. As the radius r gradually increases from 100 nm to 150 nm, and finally to 200 nm, the phase change intensifies, and the Fano resonance becomes stronger. The spectral lines gradually change from Lorentz lines to Fano lines. The reflecting unit is embedded in the strip waveguide; therefore, the diameter of the reflecting unit cannot be greater than or equal to the width of the strip waveguide, for example, 600 nm, meaning the radius r of the reflecting unit cannot be greater than or equal to 300 nm. To ensure light transmittance, the radius r of the reflecting unit is designed to be 200 nm.

[0124] In this scheme, the radius of the reflective unit is set to 200nm, which ensures the light transmittance and meets the device fabrication requirements.

[0125] In a feasible solution, such as Figure 12 As shown, the sensor also includes a substrate layer 2 disposed below the waveguide structure. The substrate layer 2 includes a first layer 21 and a second layer 22, and the substrate layers are Si and SiO2 from bottom to top, that is, the first layer is Si and the second layer is SiO2.

[0126] The sensor also includes a cladding that surrounds the waveguide structure, which can be air or an analyte.

[0127] In this solution, a complete sensor is formed by setting a cladding layer and a substrate layer, thus ensuring the reliability of the sensor.

[0128] Example 2

[0129] This embodiment describes a method for detecting mixed solutions, such as... Figure 13 As shown, the detection method includes:

[0130] S101. Using the Fano resonance-based sensor as described in Example 1, obtain the peak information of the resonance peak of the Fano resonance generated by the mixed solution, including wavelength and / or intensity.

[0131] S102. Obtain the refractive index of the mixed solution corresponding to the peak information, including the real refractive index and / or the imaginary refractive index;

[0132] S103. Based on the refractive index, the concentration of each component in the mixed solution is obtained.

[0133] Specifically, by testing the sensor, two mapping relationships can be obtained: a first mapping relationship between the wavelength of the resonance peak and the real refractive index, and a second mapping relationship between the intensity of the resonance peak and the imaginary refractive index. The first mapping relationship is linear; by converting the intensity of the resonance peak in the second mapping relationship, a second mapping relationship between the logarithm of the slope of the Fano resonance peak and the imaginary refractive index can be obtained, and the third mapping relationship is also linear.

[0134] For the detection of the mixed solution, firstly, the wavelength position and corresponding intensity of the Fano resonance peak of the solution are measured. Based on the intensity, the slope of the Fano resonance peak can be obtained, and then the logarithm of the slope can be calculated. Next, the wavelength position and the logarithm of the Fano resonance peak slope are substituted into the first and third linear relationships to obtain the real and imaginary refractive indices of the mixed solution. Finally, the real and imaginary refractive indices of the mixed solution are substituted into the equivalent complex refractive index formula to obtain the concentration of each component in the mixed solution.

[0135] This solution combines the real and imaginary refractive indices, enabling the detection of not only binary but also ternary mixed solutions without the need for functionalized cavity arrays. This improves detection efficiency, reduces detection difficulty, and expands the application range. The sensor is applicable to all ternary mixed solutions. For any ternary mixed solution containing an unknown concentration of toxic components, the sensor can detect the concentration of the toxic components, thereby determining its safety and degree of contamination.

[0136] While specific embodiments of this disclosure have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of this disclosure is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of this disclosure, but all such changes and modifications fall within the scope of protection of this disclosure.

Claims

1. A sensor based on Fano resonance, characterized in that, The sensor comprises a waveguide structure; The waveguide structure comprises a strip waveguide and a plurality of ring waveguides coupled with the strip waveguide; The strip waveguide is embedded with a plurality of reflection units, which are circular or elliptical, and the height of the reflection units is consistent with the height of the waveguide structure; The strip waveguide is used for receiving incident light; The reflection units are used for reflecting the incident light to form reflected light in a discrete state; The ring waveguides are used for circulating the incident light in the ring waveguides to form transmitted light in a continuous state; The reflected light and the transmitted light interfere with each other to produce the Fano resonance; The sensor is used for detecting the concentration of each component in a mixed solution; The concentration is based on the real part refractive index and the imaginary part refractive index of the mixed solution; The real part refractive index is based on the wavelength of the resonance peak of the Fano resonance generated by the mixed solution; The imaginary part refractive index is based on the intensity of the resonance peak of the Fano resonance generated by the mixed solution; The number of the reflection units is 3; The first center of the reflection unit in the middle position is on the same straight line as the second center of the ring waveguide, and the straight line is perpendicular to the length direction of the strip waveguide; The number of the ring waveguides is 2, and the two ring waveguides are arranged on both sides of the strip waveguide; The coupling gap between each ring waveguide and the strip waveguide is the same.

2. The Fano resonance based sensor of claim 1, wherein, The spacing between the two adjacent reflection units is 500 nm.

3. The Fano resonance based sensor of claim 1, wherein, The coupling gap is 200 nm.

4. The Fano resonance based sensor of claim 1, wherein, The material of the waveguide structure is a chalcogenide material; and / or, The height of the waveguide structure is 300 nm; and / or, The width of the waveguide structure is 600 nm; and / or, The radius of the reflection unit is 200 nm; and / or, The sensor further comprises a substrate layer arranged below the waveguide structure; and / or, The sensor further comprises a cladding layer wrapping the waveguide structure.

5. A method of detecting a mixed solution, characterized by, The detection method comprises: using the Fano resonance-based sensor according to any one of claims 1-4 to obtain peak information of a resonance peak of the Fano resonance generated by the mixed solution, the peak information including wavelength and intensity; obtaining the refractive index of the mixed solution corresponding to the peak information, the refractive index including real part refractive index and imaginary part refractive index; the real part refractive index of the mixed solution is based on the wavelength; the imaginary part refractive index of the mixed solution is based on the intensity; based on the real part refractive index and the imaginary part refractive index of the mixed solution, the concentration of each component in the mixed solution is obtained.

Images