Temperature self-compensated SPR sensor with square hole array double-layer lattice structure

Abstract

The application relates to the technical field of metal micro-nano devices and sensing, in particular to a square-hole-array double-layer-lattice-structure temperature self-compensation SPR sensor. The sensor comprises an upper square-hole-array structure, a metal film layer and a lower double-layer-lattice structure. The upper square-hole array is composed of a silicon nitride layer and a silicon dioxide layer, and the metal film is located between the upper square-hole-array structure and the lower double-layer-lattice structure. The lower double-layer-lattice structure is composed of a double-layer silicon nitride lattice array embedded in a PDMS substrate. The square-hole-array excites a hybrid surface plasmon mode as a refractive index sensing channel, and the double-layer-lattice structure excites a guided-mode-lattice-resonance mode as a temperature self-compensation channel. Through optimization of the square-hole-array period, the hole diameter, the dielectric layer thickness and the lattice geometric parameters, high-precision refractive index detection under temperature interference can be realized.

Description

Technical Field

[0001] This invention relates to the field of metal micro / nano devices and surface plasmon resonance (SPR) sensing technology, and particularly to a temperature-compensated SPR sensor with a square aperture array bilayer lattice structure. Background Technology

[0002] Surface plasmon resonance (SPR) sensors have wide applications in biochemical sensing, environmental monitoring, and medical diagnostics due to their advantages such as high sensitivity, label-free operation, and real-time detection. However, traditional SPR sensors suffer from high metal ohmic losses and low quality factors, and environmental temperature fluctuations can interfere with refractive index measurements, leading to decreased detection accuracy. By introducing dielectric waveguide layers, metal gratings, or metamaterial structures, guided mode resonance or hybrid SP modes can be excited, thereby reducing metal losses and improving the quality factor. Meanwhile, some studies have attempted to achieve temperature self-compensation using dual-channel or multi-mode structures, but these devices are often structurally complex, difficult to fabricate, and have limited resolution of temperature-compensated modes.

[0003] The purpose of this invention is to provide a temperature-compensated SPR sensor with a square aperture array double-layer lattice structure, which aims to simplify the structure while obtaining high-precision temperature-compensated refractive index detection. Summary of the Invention

[0004] The purpose of this invention is to provide a temperature self-compensating SPR sensor based on a square aperture array and a double-layer lattice structure, which aims to simplify the structure while obtaining high-precision temperature self-compensating refractive index detection.

[0005] To achieve the above objectives, the present invention provides a temperature self-compensating SPR sensor based on a square aperture array and a double-layer lattice structure, comprising: an upper square aperture array structure, a metal thin film layer, and a lower double-layer lattice structure. The upper square aperture array structure comprises a silicon nitride layer and a silicon dioxide layer stacked sequentially from top to bottom, with periodically arranged square apertures formed in the silicon nitride layer and the silicon dioxide layer. The metal thin film layer is disposed at the bottom of the silicon dioxide layer. The lower double-layer lattice structure comprises a PDMS substrate and a double-layer silicon nitride lattice array embedded in the PDMS substrate layer. The double-layer silicon nitride lattice array is composed of an upper silicon nitride lattice and a lower silicon nitride lattice, with a gap between the two lattice layers.

[0006] Furthermore, the silicon nitride layer in the upper square hole array structure has a thickness of 80~120nm, and the silicon dioxide layer has a thickness of 170~210nm.

[0007] Furthermore, the period of the upper square aperture array structure is 990~1010nm, and the width of the square aperture is 200~350nm.

[0008] Furthermore, the metal thin film layer material is gold, and the thickness of the gold film is 40~100nm.

[0009] Furthermore, the lower double-layer lattice structure PDMS substrate is made of polydimethylsiloxane material.

[0010] Furthermore, in the bilayer silicon nitride lattice array, the width of the single-layer silicon nitride lattice is 175~225nm, the height is 250~350nm, and the spacing between the two layers of silicon nitride lattice is 150~210nm.

[0011] Furthermore, the period of the double-layer silicon nitride lattice array is one-third of the period of the square hole array.

[0012] When TM-polarized light is incident perpendicularly on the sensor surface, the square aperture array excites a hybrid SP mode. The electric field of this mode is mainly localized within and around the silicon nitride and silicon dioxide layers within the square apertures, with a weaker field strength within the metal layers. This effectively suppresses ohmic losses in the metal, resulting in an extremely narrow full width at half maximum (FWHM) and a very high quality factor. This mode is highly sensitive to external refractive index changes and serves as a refractive index sensing channel. The double-layer silicon nitride lattice array excites a guided mode lattice resonance mode. Its electric field is highly localized within the lattice structure and is insensitive to changes in the refractive index of the analyte, but sensitive to temperature changes, thus serving as a temperature self-compensating channel.

[0013] Since the refractive index sensing channel is sensitive to changes in refractive index but relatively insensitive to changes in temperature, and the temperature compensation channel is sensitive to changes in temperature but relatively insensitive to changes in refractive index, by monitoring the drift of the resonant waves of the two channels and performing differential calculations, the changes in refractive index and temperature can be calculated simultaneously, thus achieving high-precision refractive index detection under temperature interference. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a three-dimensional structural schematic diagram of a temperature self-compensating SPR sensor with a square aperture array double-layer lattice structure according to the present invention.

[0016] Figure 2 This is a typical reflection spectrum of a temperature self-compensating SPR sensor with a square aperture array double-layer lattice structure according to the present invention.

[0017] Figure 3This is a correlation analysis diagram of the resonant wavelength and refractive index of different analytes for a temperature self-compensating SPR sensor with a square aperture array double-layer lattice structure according to the present invention.

[0018] Figure 4 This is a correlation analysis diagram of the resonant wavelength and different temperatures of a temperature self-compensating SPR sensor with a square aperture array double-layer lattice structure according to the present invention.

[0019] 1-Analyte, 2-Silicon nitride layer, 3-Silicon dioxide layer, 4-Metal thin film layer, 5-Silicon nitride lattice, 6-PDMS substrate. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] Please see Figure 1 The present invention provides a temperature self-compensating SPR sensor with a square aperture array double-layer lattice structure, comprising: an analyte 1, an upper square aperture array structure (containing a silicon nitride layer 2 and a silicon dioxide layer 3 and a square aperture array penetrating both layers), a metal thin film layer 4 (gold film), and a lower double-lattice structure (containing a PDMS substrate 6 and a double-layer silicon nitride lattice array 5 embedded therein).

[0022] In this embodiment, the present invention uses the finite-difference time-domain (FDTD) method to simulate the minimum periodic unit of the sensor structure and sets corresponding boundary conditions for simulation. The incident light is a TM-polarized plane wave, incident perpendicularly to the surface of the sensor structure. Periodic boundary conditions are used in the x and y directions, and perfectly matched layer boundary conditions are used in the z direction. The preferred parameters are as follows: upper silicon nitride layer thickness t1 = 100 nm, upper silicon dioxide layer thickness t2 = 190 nm, square aperture array period P = 1000 nm, and square aperture array width w. c =275nm, gold film thickness t m =60nm, the lower silicon nitride lattice length w=200nm, the lower silicon nitride lattice height h=300nm, the spacing t3=180nm of the double silicon nitride lattice, and the lattice period Pc=P / 3.

[0023] Metallic gold was described using the Drude model, and the optical constants of silicon nitride and silicon dioxide were obtained by numerical fitting of data collected by Palik. The refractive index of PDMS decreased linearly with increasing temperature, with a temperature coefficient of -4.5 × 10⁻⁶. -4 / ℃.

[0024] Please see Figure 2 When the refractive index of the analyte is 1.333, the sensor's reflectance spectrum exhibits a refractive index sensing mode at 1333 nm (denoted as m). R1 Two temperature-compensated modes (denoted as m) appear at 1406 nm and 1448 nm, respectively. T1 and m T2 The full width at half maximum (FWHM) of all three resonance peaks is relatively narrow.

[0025] Please see Figure 3 Linear fitting relationship of the sensor under different analyte refractive indices, refractive index sensing mode m R1 The redshift occurs with increasing refractive index, while the temperature-compensated mode m T1 and m T2 The resonant wavelength hardly changes with the refractive index.

[0026] Please see Figure 4 The linear fitting relationship of the sensor at different temperatures shows that all three resonant modes exhibit a blue shift with increasing temperature, and the sensing mode m... R1 The temperature drift is small, while the temperature compensation mode m T1 and m T2 The temperature drift is relatively large.

[0027] Based on the above characteristics, the three resonance modes exhibit significant differences in their responses to refractive index and temperature. By simultaneously reading the wavelength positions of the three resonance peaks, the ambient temperature change is calculated using the wavelength drift of the temperature-compensated mode. Then, the temperature-induced drift is subtracted from the total drift of the refractive index sensing mode, yielding the net drift caused solely by refractive index changes. This effectively eliminates the interference of ambient temperature fluctuations on the refractive index measurement results. Therefore, the sensor proposed in this invention is suitable for high-precision dynamic detection of the refractive index of solutions under different temperature environments.

[0028] The above description discloses only one preferred embodiment of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A temperature self-compensating SPR sensor with a square aperture array double-layer lattice structure, characterized in that, The structure includes an upper square hole array structure, a metal thin film layer, and a lower double-layer lattice structure. The upper square hole array structure comprises silicon nitride and silicon dioxide layers stacked sequentially from top to bottom, with periodically arranged square holes formed in the silicon nitride and silicon dioxide layers to form a square hole array. The metal thin film layer is disposed at the bottom of the silicon dioxide layer. The lower double-layer lattice structure comprises a PDMS substrate layer and a double-layer silicon nitride lattice array embedded in the PDMS substrate layer. The double-layer silicon nitride lattice array is composed of an upper silicon nitride lattice and a lower silicon nitride lattice, with a gap between the two lattice layers.

2. The temperature self-compensating SPR sensor with a square aperture array double-layer lattice structure as described in claim 1, characterized in that, The thickness of the silicon nitride layer is 80–120 nm, and the thickness of the silicon dioxide layer is 170–210 nm.

3. The temperature self-compensating SPR sensor with a square aperture array double-layer lattice structure as described in claim 1, characterized in that, The period of the square aperture array is 990–1010 nm, and the width of the square aperture is 200–350 nm.

4. The temperature self-compensating SPR sensor with a square aperture array double-layer lattice structure as described in claim 1, characterized in that, The metal thin film layer is made of gold and has a thickness of 40–100 nm.

5. The temperature self-compensating SPR sensor with a square aperture array double-layer lattice structure as described in claim 1, characterized in that, The PDMS substrate is made of polydimethylsiloxane.

6. The temperature self-compensating SPR sensor with a square aperture array double-layer lattice structure as described in claim 1, characterized in that, In the bilayer silicon nitride lattice array, the width of the single-layer silicon nitride lattice is 175–225 nm, the height is 250–350 nm, and the spacing between the two layers of silicon nitride lattice is 150–210 nm.

7. The temperature self-compensating SPR sensor with a square aperture array double-layer lattice structure as described in claim 1, characterized in that, The period of the double-layer silicon nitride lattice array is one-third of the period of the square hole array.

8. An application of a temperature self-compensating SPR sensor with a square aperture array double-layer lattice structure, employing the sensor as described in any one of claims 1-7, characterized in that, By monitoring the wavelength drift of the refractive index sensing resonance peak excited by the upper square aperture array and combining it with the wavelength drift of the temperature compensation mode excited by the lower double-layer silicon nitride lattice array, and utilizing the characteristics that the refractive index sensing mode is sensitive to refractive index but relatively insensitive to temperature, and the temperature compensation mode is sensitive to temperature but relatively insensitive to refractive index, temperature interference is eliminated through differential calculation of the wavelength drift in the dual channels, thereby achieving high-precision dynamic detection of the refractive index of the liquid under test at different temperatures.

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