Optical Sensor Based on High Refractive Index Difference Superstructure and Manufacturing Method

Abstract

An optical sensor based on a high refractive index difference superstructure and a manufacturing method thereof, which relates to the field of optical sensing technology, and specifically belongs to an optical sensor based on a high refractive index difference superstructure and a manufacturing method thereof. It includes a dielectric substrate and a superstructure. The superstructure is a grating unit composed of all-dielectric materials. The grating units are evenly distributed on the dielectric substrate and are periodically arranged in the X direction. The present invention uses all-dielectric materials with a high refractive index, which can avoid ohmic losses caused by metal materials. While achieving high sensitivity, it can also extend the detection wavelength range to the near-infrared band.

Description

Technical Field

[0001] The present invention relates to the field of optical sensing technology, and specifically belongs to an optical sensor based on a high refractive index difference superstructure and a manufacturing method thereof. Background Art

[0002] Sensing technology is a comprehensive technology that integrates multiple important disciplines such as electronic communication and optical fine processing. In the information-based 21st century, it has become a key technology in the information industry and the control field, gathering extremely high scientific significance and application value. With the rapid development of science and technology, new requirements such as miniaturization and integration have been put forward for sensor devices. With the great progress of nanotechnology, it has become possible to combine new nanomaterials with advanced optical sensing technology to design and manufacture a new generation of high-performance micro-nano structure optical sensors.

[0003] Currently, the research on refractive index sensors mainly focuses on metal plasmonic structures. However, due to the strong radiative loss caused by the oscillation of free electrons in metal structures, the quality factor of metal structures is usually low, which limits the application of metal plasmonic structure devices in nanophotonics.

[0004] In addition, due to different applications, the related research on optical Fano resonance has been extended from single Fano resonance to multi-Fano resonance. Multi-Fano resonance can be widely applied to multi-wavelength surface enhanced spectroscopy, multi-channel sensors, and multi-band slow light devices. However, so far, few studies can achieve three or more high-quality factor Fano resonances simultaneously. Therefore, based on the current research status of optical refractive index and the advantages of all-dielectric superstructures and Fano resonance of high refractive index materials, the inventor proposes an optical sensor based on a high refractive index difference superstructure. Summary of the Invention

[0005] The purpose of the present invention is to provide an optical sensor based on a high refractive index difference superstructure and a manufacturing method thereof, so as to achieve the performance of a high-sensitivity optical sensor.

[0006] The optical sensor based on a high refractive index difference superstructure provided by the present invention is characterized in that it includes a dielectric substrate and a superstructure. The superstructure is a grating unit composed of all-dielectric materials. The grating units are evenly distributed on the dielectric substrate and are periodically arranged in the X direction.

[0007] Furthermore, the grating uses Si as the material with a thickness of 220 nm, and the substrate uses SiO2 as the material with a thickness of 2 um. Among them, the refractive index of Si is 3.45, and the refractive index of SiO2 is 1.48.

[0008] Furthermore, the period of the grating unit is 760 nm, the width of each grating bar in each period is 125 nm, the thickness of the grating bar is 220 nm, and the spacing between adjacent grating bars is 50 nm.

[0009] Furthermore, three Fano resonance peaks are formed between 880 nm and 980 nm in the present invention.

[0010] A method for manufacturing an optical sensor based on a high refractive index difference superstructure provided by the present invention is characterized by including the following processes:

[0011] Step 1: Rinse the silica substrate with deionized aqueous solution to remove contaminants;

[0012] Step 2: Deposit a silicon thin film on the silica substrate by using a low-pressure chemical vapor deposition method;

[0013] Step 3: Spin-coat photoresist uniformly on the silicon thin film and bake it;

[0014] Step 4: Project a pattern through an electron beam lithography technique to irradiate the area to be etched, and the corresponding non-etched area is not exposed to the electron beam;

[0015] Step 5: Develop the photoresist remaining at the corresponding position after electron beam exposure. Immerse it in an inorganic weak alkaline aqueous solution. After being soaked in the developer, it needs to be baked at a high temperature to harden the photoresist in the area not exposed to the electron beam, thereby making it corrosion-resistant;

[0016] Step 6: Use inductively coupled plasma etching to obtain the required grating structure;

[0017] Step 7: Remove the photoresist and clean it with deionized plasma water to obtain the optical sensor of the present invention.

[0018] For the optical sensor and manufacturing method based on a high refractive index difference superstructure provided by the present invention, by measuring the change amount of the resonant wavelength in the transmission spectrum of the incident plane wave passing through the superstructure with respect to the environmental refractive index, the sensitivity of the refractive index sensor is calculated. In the application of the present invention, the sensor is placed in the environment to be measured. The resonant wavelength moves as the environmental refractive index changes. By calculating the change amount of the resonant wavelength shift, the change amount of the external environmental refractive index is judged. At the same time, three Fano resonance peaks are generated in the transmission spectrum line, which can provide multiple detection points. The present invention has the following positive effects:

[0019] 1. Made of all-dielectric materials, without ohmic loss. The transmission and reflection spectra generated by Fano resonance can be much narrower than those of traditional plasmonic sensors, and it is easier to achieve high quality factors, high sensitivity, and high figure of merit.

[0020] 2. The three Fano resonance peaks with narrow line widths in the transmission spectrum are easy to detect and measure, and can provide multiple detection points at the same time.

[0021] 3. The superstructure uses all-dielectric materials, is compatible with CMOS technology, has low manufacturing costs, and is expected to achieve high-performance, miniaturized, and highly integrated photonic devices.

[0022] 4. The refractive index sensor described in the present invention can be applied to related fields such as gas, liquid and biosensing, and can bring great convenience to industry experimental measurements. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the present invention;

[0024] Figure 2 It is a schematic diagram of the cross-sectional structure of the present invention;

[0025] Figure 3 is a transmission curve of the resonance mode at different refractive indices of the medium to be measured at the first Fano resonance (P1) in a specific embodiment of the present invention;

[0026] Figure 4 is a transmission curve of the resonance mode at different refractive indices of the medium to be measured at the second Fano resonance (P2) in a specific embodiment of the present invention;

[0027] Figure 5 is a transmission curve of the resonance mode at the third Fano resonance (P3) under different refractive indices of the medium to be measured in a specific embodiment of the present invention;

[0028] Figure 6 It is a production flow chart of the present invention. DETAILED DESCRIPTION

[0029] like Figure 1-2 As shown, the optical sensor based on the high refractive index difference superstructure provided by the present invention is specifically composed of a dielectric substrate 2 and a grating unit 1 stacked in sequence from bottom to top. The material of the grating unit is Si, and the material of the dielectric substrate is SiO2, and the refractive indices are nsi=3.45 and nsio2=1.48 respectively. The grating unit is considered to be infinite in the y direction and periodic in the x direction. In a specific embodiment of the present invention, the period P of the grating unit is 760nm, the width W of each grating bar in each period is 125nm, the thickness tg of the grating bar is 220nm, and the thickness of the dielectric substrate is 2um. The spacing between two grating bars is d=50nm, and the working wavelength of the above-mentioned embodiment of the present invention is between 880nm-980nm.

[0030] like Figure 6As shown in the figure, a manufacturing method of an optical sensor based on a high refractive index difference superstructure provided by the present invention includes:

[0031] Step 1: Use deionized aqueous solution to rinse the silica substrate to remove contaminants;

[0032] Step 2: Deposit a silicon thin film on the silica substrate by using low-pressure chemical vapor deposition method;

[0033] Step 3: Spin-coat photoresist uniformly on the silicon thin film and bake it;

[0034] Step 4: Project a pattern through electron beam lithography technology to irradiate the area to be etched, and the corresponding non-rectangular area is not exposed to the electron beam;

[0035] Step 5: Develop the photoresist remaining at the corresponding position after electron beam exposure, immerse it in an inorganic weak alkaline aqueous solution, and perform high-temperature baking after being soaked in the developer to harden the glue in the area not exposed to the electron beam and make it corrosion-resistant;

[0036] Step 6: Use inductively coupled plasma etching to obtain the required grating structure;

[0037] Step 7: Remove the photoresist and clean it with deionized water to obtain the optical sensor of the present invention.

[0038] The present invention is composed of a silicon plane - silica base, and has the characteristics of being easy to implement, small in size, and easy to integrate devices, and can realize high-performance, miniaturized, and highly integrated photonic devices. By using all-dielectric materials with high refractive indices, it can avoid ohmic losses caused by metal materials, is beneficial to achieving high sensitivity, and can also extend the detection wavelength range to the near-infrared band.

[0039] As Figures 3-5 shown, through the transmission spectra of the optical sensor based on the high refractive index difference superstructure of the present invention in different refractive index environments in specific examples, the application and technical effects of the present invention are further described and illustrated. Among them, the refractive indices n of the substances to be measured are 1.33, 1.34, and 1.35 respectively.

[0040] When the refractive index of the substance to be measured changes in the gaps above and between the superstructures, the transmission spectrum response of the incident plane wave is simulated using the finite element method. When using the finite element method for simulation, the x-direction is set as the periodic boundary condition, and the y-direction is set as the perfectly matched layer. A plane wave is vertically incident on the grating layer, and the plane wave interacts with the dielectric material. Three Fano resonance peaks with narrow line widths can be obtained in the transmission spectrum, and the wavelength range of the transmission spectrum is 890 nm - 980 nm. When the refractive indices of the gaps of the superstructure and the substance to be measured above are 1.33, 1.34, and 1.35, although the refractive index change range is very small, the peak positions of the Fano resonance still move substantially with the change of the refractive index. Therefore, the change of the refractive index can be obtained through the change of the resonance wavelength, and the refractive index sensing detection of the substance to be measured is completed. Reference Figures 3-5 The transverse shift phenomenon of the resonance peaks in the transmission spectrum diagram.

[0041] The sensitivity of the optical sensor of the present invention is defined as the change amount of the resonance wavelength caused by the unit refractive index, that is, the sensitivity S = Δλ / Δn, where Δλ is the shift amount of the Fano resonance wavelength when the refractive index changes, and Δn is the change amount of the refractive index of the medium. The three Fano resonance modes appearing in this transmission spectrum diagram are P1, P2, and P3 respectively. When the refractive index changes from 1.33 to 1.35, it can be seen that the resonance wavelengths corresponding to P1, P2, and P3 all move to the right with the increase of the refractive index. The shift amount of the resonance wavelength when the refractive index changes is Δλ. Therefore, the shift amount Δλ corresponding to the P1 resonance wavelength is 10.568 nm, Δn = 0.02; the shift amount Δλ corresponding to the P2 resonance wavelength is 3.968 nm, Δn = 0.02; the shift amount Δλ corresponding to the P3 resonance wavelength is 12.85 nm, Δn = 0.02; the sensitivities of the three Fano resonances are calculated by the formula S = Δλ / Δn, which are S(P1) = 528.4 nm / RIU, S(P2) = 198.4 nm / RIU, and S(P3) = 642.5 nm / RIU respectively. The present invention can form three Fano resonance peaks in the spectral range of 880 - 980 nm, the modulation depth can exceed 99%, nearly 100%, and the maximum sensitivity is 642.5 nm / RIU.

[0042] The present invention is composed of all-dielectric materials, has no ohmic loss, can be used for the detection of gases and liquids with different refractive indices, and can provide further help for the development of sensing, lasers, and nonlinear optics. The present invention can realize the detection of substances to be measured such as gases and liquids with different refractive indices, and plays an important role in the fields of chemistry, medicine, integrated optics, etc.

Claims

1. An optical sensor based on a high refractive index difference superstructure, characterized in that, It includes a dielectric substrate and a superstructure. The superstructure is a grating unit composed of all-dielectric materials. The grating units are evenly distributed on the dielectric substrate and arranged periodically in the X direction. Among them, the grating is made of material Si with a thickness of 220 nm, and the substrate is made of material SiO2 with a thickness of 2 μm. Among them, the refractive index corresponding to Si is 3.45, and the refractive index corresponding to SiO2 is 1.

48. The period of the grating unit is 760 nm. The width of each grating bar in each period is 125 nm, the thickness of the grating bar is 220 nm, and the spacing between adjacent grating bars is 50 nm. The transmission spectrum of the optical sensor forms 3 Fano resonance peaks between 880 nm and 980 nm. According to the manufacturing method of an optical sensor based on a superstructure with a high refractive index difference, the following process is also included: Step 1: Rinse the silica substrate with deionized aqueous solution to remove contaminants; Step 2: Deposit a silicon thin film on the silica substrate by using the low-pressure chemical vapor deposition method; Step 3: Spin-coat the photoresist evenly on the silicon thin film and bake it; Step 4: Project a pattern through electron beam lithography technology to irradiate the area to be etched, and the corresponding non-etched area is not exposed to the electron beam; Step 5: Develop the photoresist remaining at the corresponding position after electron beam exposure. Immerse it in an inorganic weak alkaline aqueous solution. After being soaked in the developer, high-temperature baking is required to harden the glue in the area not exposed to the electron beam and make it corrosion-resistant; Step 6: Use inductively coupled plasma etching to obtain the required grating structure; Step 7: Remove the photoresist and clean it with deionized water to obtain the optical sensor.

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