A high FOM biochemical sensor in the visible light band

Abstract

The present invention relates to the field of metal micro-nano devices, and specifically to a high-FOM biochemical sensor in the visible light band. The sensor comprises a high- and low-refractive-index dielectric layer hybrid structure composed of an upper low-refractive-index layer and a lower high-refractive-index layer. Multiple high- and low-refractive-index dielectric layer hybrid structures are sequentially connected, with a low-refractive-index substrate disposed at the bottom of the multiple high- and low-refractive-index dielectric layer hybrid structures. A high-refractive-index graphene layer is disposed on top of the high- and low-refractive-index dielectric layer hybrid structures. The graphene layer itself is disposed on top of the high-refractive-index layer. A cavity structure layer is disposed on top of the graphene layer. A periodic subwavelength metal grating array is disposed on top of the cavity structure layer. The sensor's sensitivity and quality factor are adjusted by optimizing the structural parameters of the high / low-refractive-index dielectric layer hybrid structure, the cavity length and width of the cavity structure, the grating width and height, and the period of the periodic subwavelength metal grating array, thereby achieving a high level of comprehensive evaluation indicators.

Description

Technical Field

[0001] The present invention relates to the field of metal micro-nano devices, and in particular to a high-FOM biochemical sensor in the visible light band. Background Art

[0002] With the continuous deepening of theoretical research on nanomaterials and nanostructures and the continuous development of processing technologies in recent years, subwavelength metal gratings have become a research hotspot. Utilizing the diffraction properties of gratings, optical devices with subwavelength metal gratings can achieve many optical functions that are difficult to achieve with traditional optical devices. Therefore, subwavelength gratings are widely used in various fields such as filtering, detection, integrated optics, optical switches, and biosensing. Generally speaking, sensors based on subwavelength metal gratings either use metal surface plasmon resonance to achieve sensing, or use a planar waveguide layer and a dielectric grating structure to generate a guided mode resonance (GMR) mode. The corresponding resonant wavelength is very sensitive to changes in the refractive index of the surrounding environment, thereby achieving sensing functions.

[0003] The purpose of the present invention is to provide a high FOM biochemical sensor in the visible light band with a simple structure, aiming to simultaneously obtain higher S and FOM sensing indicators. Summary of the Invention

[0004] The purpose of the present invention is to provide a high FOM biochemical sensor in the visible light band, aiming to simultaneously obtain higher S and FOM sensing indicators and simplify the sensor structure.

[0005] To achieve the above objectives, the present invention provides a high FOM biochemical sensor in the visible light band, comprising a multilayer film structure, a periodic subwavelength metal grating array and a graphene layer. The multilayer film structure comprises a plurality of high- and low-refractive-index medium layer mixed structures and a low-refractive-index substrate. The high- and low-refractive-index medium layer mixed structure is composed of an upper low-refractive-index layer and a lower high-refractive-index layer. The plurality of high- and low-refractive-index medium layer mixed structures are connected in sequence. The low-refractive-index substrate is arranged at the bottom of the plurality of high- and low-refractive-index medium layer mixed structures. The graphene layer comprises a high-refractive layer, a graphene layer body and a cavity structure layer. The high-refractive layer is arranged on top of the high- and low-refractive-index medium layer mixed structure, the graphene layer body is arranged on top of the high-refractive layer, the cavity structure layer is arranged on top of the graphene layer, and the periodic subwavelength metal grating array is arranged on top of the cavity structure layer.

[0006] Wherein, the number of the high- and low-refractive-index medium layer hybrid structures is two.

[0007] The thickness of the low refractive index layer in the high- and low-refractive index medium layer hybrid structure is 50-200 nm, and the thickness of the high refractive index layer in the high- and low-refractive index medium layer hybrid structure is 200-250 nm.

[0008] The periodic sub-wavelength metal grating array is composed of a plurality of sub-wavelength metal gratings placed in parallel, the width of the sub-wavelength metal grating is 380-420 nm, the thickness is 30-50 nm, and the array period is 450-550 nm.

[0009] The cavity structure has a cavity width of 250 to 350 nm and a cavity length of 40 to 80 nm.

[0010] The low refractive index layer of the graphene layer has a thickness of 50 to 150 nm, and the high refractive index layer of the graphene layer has a thickness of 150 to 300 nm.

[0011] In a second aspect, the present invention provides an application of a high FOM biochemical sensor in the visible light band, including observing the drift of the resonance wavelength of the high FOM biochemical sensor to achieve real-time dynamic monitoring of the water content of heavy oil in industrial production.

[0012] The high FOM biochemical sensor in the visible light band of the present invention produces a diffraction effect when the incident light irradiates the surface of the periodic metal grating, and the redistribution of the diffracted photons will cause the Wood anomaly phenomenon. Wood =P*n, where n is the refractive index of the external environment and P is the period of the nanostructure. According to the formula S = Δλ / Δn = P*Δn / Δn = P, the sensing characteristics can be approximated. Simultaneously, the guided mode in the multilayer film structure couples with the SP mode at the metal grating, resulting in a hybrid SP mode that suppresses transmission. Furthermore, TM-polarized light can excite the cavity resonance within the nanoslit, generating a cavity mode that supports light transmission. Therefore, based on the synergistic effect of the suppression mode and the transmission mode, by modulating the hybrid SP mode to tailor the transmission peak edge generated by the cavity mode, a transmission peak with a relatively small full-width at half-height (FWHM) can be obtained. Dynamic, real-time monitoring of changes in the external refractive index can be achieved by shifting the transmission peak wavelength. By optimizing the thickness of the high / low refractive index dielectric layer hybrid structure, the cavity length and width of the cavity structure, the grating width and height, and the period of the periodic subwavelength metal grating array, the sensor's sensitivity and quality factor can be adjusted, achieving simultaneously high levels of both comprehensive evaluation indicators. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1This is a structural diagram of a high FOM biochemical sensor in the visible light band of the present invention;

[0015] Figure 2 is a drift diagram of the resonance wavelength of the sensor under different water content percentages of the present invention;

[0016] Figure 3 This is a linear fitting relationship diagram between the water content percentage of heavy oil and the resonance wavelength of the present invention.

[0017] 1-multilayer film structure, 2-periodic subwavelength metal grating array, 3-graphene layer, 11-hybrid structure of high and low refractive index dielectric layers, 12-low refractive index substrate, 31-high refractive index layer, 32-graphene layer body, 33-cavity structure layer, 111-low refractive index layer, 112-high refractive index layer. DETAILED DESCRIPTION

[0018] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0019] See also Figures 1 to 3 The present invention provides a high FOM biochemical sensor in the visible light band, comprising: a multilayer film structure 1, a periodic subwavelength metal grating array 2 and a graphene layer 3, wherein the multilayer film structure 1 comprises a plurality of high- and low-refractive-index dielectric layer hybrid structures 11 and a low-refractive-index substrate 12, wherein the high- and low-refractive-index dielectric layer hybrid structure 11 is composed of an upper low-refractive-index layer 111 and a lower high-refractive-index layer 112, and the plurality of high- and low-refractive-index dielectric layer hybrid structures 11 are connected in sequence, and the low-refractive-index substrate 12 is arranged at the bottom of the plurality of high- and low-refractive-index dielectric layer hybrid structures 11; the graphene layer 3 comprises a high-refractive-index layer 31, a graphene layer body 32 and a cavity structure layer 33, wherein the high-refractive-index layer 31 is arranged on top of the high- and low-refractive-index dielectric layer hybrid structure 11, the graphene layer body 32 is arranged on top of the high-refractive-index layer 31, the cavity structure layer 33 is arranged on top of the graphene layer 3, and the periodic subwavelength metal grating array 2 is arranged on top of the cavity structure layer 33. The number of the high- and low-refractive-index medium layer hybrid structures 11 is two.

[0020] In this embodiment, the high refractive index layer 31 and the high refractive index layer 112 have the same structure. The present invention simulates the minimum periodic structure of the sensor device structure by using the finite difference time domain method (FDTD), sets corresponding boundary conditions for simulation, measures corresponding simulation results, and uses the simulation data to prove the beneficial effects of the high FOM biochemical sensor device structure. The incident light is a TM polarized plane wave, which is perpendicular to the surface of the periodic subwavelength metal grating array 2 structure. Periodic boundary conditions are used in the x and y directions; and a perfectly matched layer (PML) boundary condition is used in the z direction. Among them, the various parameters are preferably as follows: the period of the periodic subwavelength metal grating array 2 is P = 500nm, the width of the subwavelength metal grating is w = 400nm, the thickness of the metal grating is t = 40nm, and the thickness of the low refractive index layer 33 in the graphene layer 3 is t L1 =100 nm, the thickness of the high refractive index layer 31 is t H1 =250nm, the cavity width w of the cavity structure Q =380nm, cavity length t Q =80nm, thickness t of the high and low refractive index medium layer hybrid structure 11 L =100nm, high refractive index layer 112 (HID) thickness t H =250nm, the cavity width w of the cavity structure Q =380nm, cavity length t Q =80nm.

[0021] The material used for the periodic subwavelength metal grating is silver (Ag), the material for the low-refractive-index medium is silicon dioxide (SiO2), and the material for the high-refractive-index medium is silicon nitride (Si3N4). The dielectric constants of silver, silicon dioxide, and silicon nitride are based on the model in the Palik manual.

[0022] When the incident light hits the surface of a periodic metal grating, a diffraction effect occurs, and the redistribution of diffracted photons will lead to the Wood anomaly phenomenon. Wood=P*n, n is the refractive index of the external environment, and P is the period of the nanostructure. According to the formula S=Δλ / Δn=P*Δn / Δn=P, the sensing characteristics can be approximately obtained. At the same time, the guided mode in the multilayer film structure 1 couples with the SP mode at the metal grating, resulting in a hybrid SP mode that suppresses transmission. And the TM polarized light can excite the cavity resonance in the nanoslit, generating a cavity mode that supports light transmission. Therefore, based on the synergistic effect of the suppression mode and the transmission mode, that is, by modulating the hybrid SP mode to trim the transmission peak edge generated by the cavity mode, a transmission peak with a relatively small half-width full height (FWHM) can be obtained. Dynamic real-time monitoring of changes in the external environment can be achieved based on the shift of the transmission peak wavelength. By optimizing the thickness of the high / low refractive index high and low refractive index medium layer hybrid structure 11, the cavity length and cavity width of the cavity structure, and the structural parameters of the period P of the periodic subwavelength metal grating array 2, the sensitivity and quality factor of the sensor can be adjusted, so that the two comprehensive evaluation indicators of the sensor can reach a high level at the same time.

[0023] The present invention provides a design of a high FOM biochemical sensor device in the visible light band. According to the transmission spectrum obtained by numerical simulation, Figure 2 When the grating width and height, and the period of the periodic subwavelength metal grating array, are 500 nm, the resonance peak is observed to change by changing the ambient refractive index. The sensitivity can be calculated to be 499.9 nm / RIU, with a FWHM of 3 nm and a FOM of 499.9 / 3 = 166.6 RIU-1. Therefore, we believe that this sensor device can achieve both high sensitivity and quality factor.

[0024] In addition to the parameters selected above, the optional parameter range also includes the thickness of the low-refractive-index high-low-refractive-index medium layer hybrid structure 11 being 50 to 200 nm, and the thickness of the high-refractive-index low-refractive-index medium layer hybrid structure 11 being 200 to 250 nm. The periodic subwavelength metal grating array 2 is composed of multiple parallel subwavelength metal gratings, the width of the subwavelength metal grating is 380 to 420 nm, the thickness is 30 to 50 nm, and the array period is 450 to 550 nm. The thickness of the low-refractive-index layer in the graphene layer is 50 to 150 nm, the thickness of the high-refractive-index layer in the graphene layer is 150 to 300 nm, the cavity width of the cavity structure is 250 to 350 nm, and the cavity length is 40 to 80 nm.

[0025] In a second aspect, the present invention provides an application of a high FOM biochemical sensor in the visible light band, including observing the drift of the resonance wavelength of the high FOM biochemical sensor to achieve real-time dynamic monitoring of the water content of heavy oil in industrial production.

[0026] The range of refractive index variation in the external environment of the structure proposed in this invention is derived from simulations of water-containing heavy oil. When the water content of heavy oil is relatively high, the vaporization of water can reduce the combustion temperature and calorific value, affecting the normal operation of metal smelting equipment. Therefore, monitoring the water content is necessary to address this issue. The formula for the refractive index and volume percentage of water-containing heavy oil is:

[0027] lnn=Dlnn1+(1-D)lnn2

[0028] Where n is the refractive index of the water-containing heavy oil, n1 represents the refractive index of pure water, n2 represents the refractive index of pure heavy oil, and D represents the percentage of water in the heavy oil by volume.

[0029] Table 1 Comparison of water content and refractive index of heavy oil

[0030]

[0031] The present invention provides a design of a high FOM chemical sensor device in the visible light band. According to the transmission spectrum obtained by numerical simulation, the water percentage is fitted with the corresponding resonance wavelength data, such as Figure 2 、 3 As shown in the figure, by varying the ambient refractive index, the resonance peak shifts. The calculated sensitivity is 499.9 nm / RIU, with a Full Width Half Maximum (FWHM) of 3 nm and a Field of View (FOM) of 499.9 / 3 (166.6 RIU-1). Therefore, we believe that this sensor achieves both high sensitivity and a high quality factor. Furthermore, the wavelength of the resonance peak exhibits a good linear relationship with the water content, indicating the excellent stability of the sensor structure. By observing the drift of the resonance wavelength, the water content of heavy oil in industrial production can be monitored in real time.

[0032] The above disclosure is only a preferred embodiment of the present invention, and certainly cannot be used to limit the scope of the rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A high FOM biochemical sensor in the visible light band, characterized in that: The invention comprises a multilayer film structure, a periodic subwavelength metal grating array and a graphene layer, wherein the multilayer film structure comprises a plurality of high- and low-refractive-index medium layer hybrid structures and a low-refractive-index substrate, wherein the high- and low-refractive-index medium layer hybrid structure is composed of an upper low-refractive-index layer and a lower high-refractive-index layer, wherein the plurality of high- and low-refractive-index medium layer hybrid structures are sequentially connected, and the low-refractive-index substrate is arranged at the bottom of the plurality of high- and low-refractive-index medium layer hybrid structures, and the graphene layer comprises a high-refractive-index layer, a graphene layer body and a cavity structure layer, wherein the high-refractive-index layer is arranged on top of the high- and low-refractive-index medium layer hybrid structure, the graphene layer body is arranged on top of the high-refractive-index layer, the cavity structure layer is arranged on top of the graphene layer, and the periodic subwavelength metal grating array is arranged on top of the cavity structure layer; The number of the high- and low-refractive-index medium layer hybrid structures is two, the thickness of the low-refractive-index layer in the high- and low-refractive-index medium layer hybrid structure is 50 to 200 nm, the thickness of the high-refractive-index layer in the high- and low-refractive-index medium layer hybrid structure is 200 to 250 nm, and the periodic subwavelength metal grating array is composed of multiple parallel subwavelength metal gratings, the width of the subwavelength metal grating is 380 to 420 nm, the thickness is 30 to 50 nm, and the array period is 450 to 550 nm.

2. A high FOM biochemical sensor in the visible light band as claimed in claim 1, characterized in that: The cavity structure has a cavity width of 250 to 350 nm and a cavity length of 40 to 80 nm.

3. The high FOM biochemical sensor in the visible light band according to claim 1, characterized in that: The thickness of the low refractive index layer of the graphene layer is 50-150 nm, and the thickness of the high refractive index layer of the graphene layer is 150-300 nm.

4. An application of a high FOM biochemical sensor in the visible light band, using a high FOM biochemical sensor in the visible light band according to any one of claims 1 to 3, characterized in that: By observing the drift of the resonance wavelength of the high FOM biochemical sensor, real-time dynamic monitoring of the water content of heavy oil in industrial production can be achieved.

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