Optical sensor based on surface lattice resonance and method for testing thereof

Abstract

The application discloses an optical sensor based on surface lattice resonance and a testing method thereof. The optical sensor based on surface lattice resonance comprises a substrate and a silicon / silica nanocolumn dimer array on the substrate. The silicon / silica nanocolumn dimer array is periodically and uniformly arranged by silicon / silica nanocolumn dimers. The silicon / silica nanocolumn dimer comprises two silicon / silica nanocolumns arranged at intervals. The surface lattice resonance of the optical sensor based on surface lattice resonance is adjustable, and the surface lattice resonance has a narrow bandwidth and a highly enhanced local electromagnetic field, so that the sensitivity and the quality factor of sensing can be effectively enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of optical sensors based on surface lattice resonance and its testing method. BACKGROUND

[0002] Surface lattice resonance (SLR) is a kind of high quality factor resonance mode generated by the coupling of localized surface plasmon resonance of metal nanoparticles in periodic array of metal nanoparticles and array surface diffraction wave. SLR can well localize the incident field energy in array structure, effectively suppresses the radiation loss of system, and significantly increases the localized electromagnetic field strength. SLR is very sensitive to the change of refractive index of surrounding medium environment due to its localized field, and can be applied to optical sensors. The sensing performance of SLR sensor is mainly determined by sensitivity and quality factor. Generally speaking, improving sensitivity requires improving the localized field strength of SLR; improving quality factor requires reducing the bandwidth of SLR or improving sensitivity. However, the substrate effect will weaken the localized field strength of SLR and increase its bandwidth. In addition, the intrinsic loss characteristics of metal material will also limit its further development in SLR sensor, for example, a refractive index sensor of gold nanoparticle array directly placed on a quartz substrate, due to its wide SLR bandwidth, the quality factor is only 25 [P. Offermans, M. C. Schaafsma, S. R. K. Rodriguez, Y. Zhang, M. Crego-calama, S. H. Brongersma, and J. G. Rivas, "Universal Scaling of the Figure of Merit of Plasmonic Sensor", ACS Nano (2011) 5 (6), 5151-5157]. SUMMARY

[0003] The technical problem to be solved by the present application is to overcome the defects of the prior art, and to provide an optical sensor based on surface lattice resonance, which has adjustable surface lattice resonance, and the surface lattice resonance has a narrow bandwidth and a highly enhanced localized electromagnetic field, which can effectively enhance the sensitivity and quality factor of the sensor.

[0004] To solve the above technical problems, the technical scheme of the present application is: an optical sensor based on surface lattice resonance, comprising a substrate and a silicon / silicon dioxide nanocolumn dimer array on the substrate; wherein,

[0005] The silicon / silicon dioxide nanocolumn dimer array is periodically and uniformly arranged by silicon / silicon dioxide nanocolumn dimers;

[0006] The silicon / silica nanocolumn dimer comprises two silicon / silica nanocolumns arranged at intervals.

[0007] Further, the silicon / silica nanocolumn comprises a silicon nanocolumn and a silica nanocolumn arranged in sequence from top to bottom.

[0008] Further, the silicon nanocolumn and the silica nanocolumn in the same silicon / silica nanocolumn have the same diameter;

[0009] The silicon nanocolumn and the silica nanocolumn in the same silicon / silica nanocolumn are completely coincident in the up-down direction.

[0010] Further, the diameter of the silicon / silica nanocolumn is 60-300 nm.

[0011] Further, the height H1 of the silicon nanocolumn is 50-300 nm; and the height H2 of the silica nanocolumn is 100-900 nm.

[0012] Further, the silicon / silica nanocolumn dimer array is formed by uniformly arranging the silicon / silica nanocolumn dimers in the X direction and the Y direction with the same period P.

[0013] Further, the period P is 300-1000 nm.

[0014] Further, the center distance L between the two silicon / silica nanocolumns in the silicon / silica nanocolumn dimer is 70-400 nm.

[0015] Further, the material of the substrate is glass or quartz.

[0016] The application also provides a testing method of a surface lattice resonance-based optical sensor, and the method steps comprise:

[0017] The step of calculating the transmission spectrum comprises: using the finite difference time domain method to perform simulation calculation, first constructing a physical model of a periodic unit in the surface lattice resonance-based optical sensor, setting a perfect matched layer on the upper and lower boundaries thereof, setting a periodic boundary condition on the four surrounding boundaries, setting a vertical incident plane wave on the upper surface, and calculating the transmission spectrum of the corresponding physical model; wherein the transmission valley in the transmission spectrum corresponds to the surface lattice resonance;

[0018] Changing the environmental refractive index, and according to the step of calculating the transmission spectrum, calculating different transmission spectra corresponding to different environmental refractive indices;

[0019] According to different transmission spectra corresponding to different environmental refractive indexes, surface lattice resonance wavelengths under different environmental refractive indexes are obtained, a change amount of the surface lattice resonance wavelength caused by a unit refractive index is calculated, and a sensitivity of the optical sensor based on the surface lattice resonance is obtained.

[0020] According to the surface lattice resonance bandwidth obtained from the transmission spectrum, the sensitivity is divided by the surface lattice resonance bandwidth, and a quality factor of the optical sensor based on the surface lattice resonance is obtained.

[0021] After the above technical scheme is adopted, the optical sensor based on the surface lattice resonance of the application supports adjustable SLR, and the SLR of the sensor is determined by the coupling effect between the Mie resonance of the silicon nanocolumn and the silicon dioxide nanocolumn, the interference effect between the two silicon / silicon dioxide nanocolumns in the silicon / silicon dioxide nanocolumn dimer, and the diffraction effect of the periodic array, wherein the Mie resonance of the silicon nanocolumn is related to factors such as the size of the silicon nanocolumn, the surrounding environment, the size and height of the silicon dioxide nanocolumn; the coupling effect between the silicon / silicon dioxide nanocolumn dimer is related to the gap between the two silicon / silicon dioxide nanocolumns, and the diffraction of the periodic array is related to factors such as the period and the incident direction. Therefore, through optimization of the structural parameters, the silicon / silicon dioxide nanocolumn dimer and the surface wave of the array can be strongly coupled to form a SLR with a narrow bandwidth and a significantly enhanced local field, which can effectively enhance the sensing sensitivity and the quality factor. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 FIG. 1 is a structural schematic diagram of the optical sensor based on the surface lattice resonance of the application;

[0023] Figure 2 FIG. 2 is a front view of the optical sensor based on the surface lattice resonance of the application; Figure 1

[0024] Figure 3 FIG. 5 is the transmission spectrum of the optical sensor based on the surface lattice resonance in Example 1 in different refractive index environments;

[0025] Figure 4 FIG. 6 is a point diagram of the relationship between the SLR wavelength of the optical sensor based on the surface lattice resonance in Example 1 and the refractive index of the medium environment;

[0026] Figure 5 FIG. 7 is a structural schematic diagram of the sensor in Comparative Example 1;

[0027] Figure 6 FIG. 8 is a comparison diagram of the transmission spectrum of the optical sensor based on the surface lattice resonance in Example 1 and the sensor in Comparative Example 1 under the same environment and parameters. DETAILED DESCRIPTION

[0028] ​For the purpose of making the subject matter of the present application more readily and clearly understood, the present application will be further described in detail below with reference to specific embodiments and in conjunction with the accompanying drawings.

[0029] As shown in Figure 1 , 2 , an optical sensor based on surface lattice resonance comprises a substrate 1 and a silicon / silica nanocolumn dimer array on the substrate 1; wherein,

[0030] The silicon / silica nanocolumn dimer array is formed by periodically and uniformly arranging silicon / silica nanocolumn dimers.

[0031] The silicon / silica nanocolumn dimer comprises two silicon / silica nanocolumns arranged at intervals.

[0032] As shown in Figure 1 , 2 , the silicon / silica nanocolumn comprises a silicon nanocolumn 2 and a silica nanocolumn 3 arranged in sequence from top to bottom.

[0033] As shown in Figure 1 , the silicon nanocolumn 2 and the silica nanocolumn 3 in the same silicon / silica nanocolumn have the same diameter.

[0034] The silicon nanocolumn 2 and the silica nanocolumn 3 in the same silicon / silica nanocolumn are completely coincident in the up-down direction.

[0035] The diameter of the silicon / silica nanocolumn is 60-300 nm. The diameters of the two silicon / silica nanocolumns in the same silicon / silica nanocolumn dimer can be the same or different. The height H1 of the silicon nanocolumn 2 is 50-300 nm; the height H2 of the silica nanocolumn 3 is 100-900 nm. The silicon / silica nanocolumn dimer array is formed by uniformly arranging the silicon / silica nanocolumn dimers in the X direction and the Y direction with the same period P. The period P is 300-1000 nm. The center distance L between the two silicon / silica nanocolumns in the silicon / silica nanocolumn dimer is 70-400 nm. The material of the substrate 1 is glass or quartz.

[0036] Embodiment 1

[0037] As shown in Figure 1 , 2As shown, an optical sensor based on surface lattice resonance, comprising a quartz substrate and a silicon / silica nanorod dimer array on the quartz substrate; the silicon / silica nanorod dimer array is periodically and uniformly arranged by silicon / silica nanorod dimers; the silicon / silica nanorod dimer comprises two silicon / silica nanorods arranged at intervals, and the silicon / silica nanorod comprises a silicon nanorod 2 and a silica nanorod 3 arranged in sequence from top to bottom.

[0038] The diameters of the two silicon / silica nanorods in the silicon / silica nanorod dimer are both 80 nm, the height H1 of the silicon nanorod 2 is 100 nm, the height H2 of the silica nanorod 3 is 900 nm, and the center distance L between the two silicon / silica nanorods in the silicon / silica nanorod dimer is 90 nm; the period P of the array is 500 nm.

[0039] The sensitivity and the quality factor of the optical sensor based on surface lattice resonance in Example 1 are tested by the following steps:

[0040] Step a: simulation calculation is performed by using the finite difference time domain method, first a physical model of a periodic unit in the sensor is constructed, perfect matched layers are set on the upper and lower boundaries, periodic boundary conditions are set on the four surrounding boundaries, and a plane wave is set on the upper surface of the physical model, which is vertically incident along the z direction and the electric field is polarized along the x direction, the transmission spectrum of the corresponding physical model is calculated, and the transmission valley in the transmission spectrum corresponds to SLR;

[0041] Step b: in the process of increasing the environmental refractive index from 1.0 to 1.1, according to step a, the different transmission spectra corresponding to different environmental refractive indices are calculated, and the different transmission spectra corresponding to different environmental refractive indices are as shown in Figure 3 , in which n represents the environmental refractive index; Figure 3

[0042] Step c: draw the relationship point diagram of SLR wavelength and medium environmental refractive index in different refractive index environments, and the relationship point diagram is as shown in Figure 4 , the calculated sensitivity is about 490 nm / unit refractive index;

[0043] Step d: according to the transmission spectrum as shown in Figure 3 , the SLR bandwidth is obtained, when the environmental refractive index is 1, the SLR bandwidth is about 4.2 nm, and then the sensitivity is divided by the SLR bandwidth to obtain the quality factor of the sensor in Example 1, which is about 117.

[0044] Comparative Example 1

[0045] As shown in Figure 5 ​As shown, a sensor comprises a quartz substrate and an array of silicon / silica nanopillars situated on the quartz substrate. The silicon / silica nanopillar array is composed of periodically and uniformly arranged silicon / silica nanopillars, each comprising an upper layer of silicon nanopillars 2 and a lower layer of silica nanopillars 3. The upper silicon nanopillars 2 and the lower silica nanopillars 3 have the same diameter, both 80 nm; the height H1 of the silicon nanopillars 2 is 100 nm; the height H2 of the silica nanopillars 3 is 900 nm; and the array period P is 500 nm.

[0046] The finite-difference time-domain method was used to simulate Comparative Example 1. First, a physical model of a periodic unit in the sensor of Comparative Example 1 was constructed. A perfectly matched layer was set on its upper and lower boundaries, and periodic boundary conditions were set on its four sides. A plane wave with a vertical incident z-direction and an electric field polarized x-direction was set on its upper surface. The transmission spectrum corresponding to the refractive index of the environment was calculated.

[0047] Figure 5 The transmission spectra of the sensor in Example 1 and the sensor in Comparative Example 1 are shown under the same environmental conditions and parameters. From... Figure 5 It can be seen that the transmission spectrum of the sensor in Example 1 has a sharp transmission valley, which corresponds to SLR, while the transmission valley of the sensor in Comparative Example 1 is very weak and almost negligible. This indicates that the SLR intensity of Comparative Example 1 is very weak, and therefore Comparative Example 1 is not suitable for sensing. This shows that compared to silicon / silica nanopillar arrays, the introduction of dimers in silicon / silica nanopillar dimer arrays further improves the SLR intensity, making it more favorable for sensing.

[0048] The optical sensor based on surface lattice resonance provided by the application supports adjustable SLR, has a narrow bandwidth and a highly enhanced local electromagnetic field, and can effectively enhance the sensing sensitivity and the quality factor. Compared with the existing metal nanoparticle periodic array sensor, the silicon / silica nanocolumn material in the sensor of the application has lower absorption loss than the metal material, can provide a narrower SLR bandwidth, and improve the quality factor of the sensor. Compared with the silicon / silica nanocolumn periodic array sensor, the silicon / silica nanocolumns in the sensor of the application are first composed into dimers and then arranged into a periodic array. The interference between the two silicon / silica nanocolumns in the silicon / silica nanocolumn dimer can further improve the local field strength of the Mie resonance of the silicon nanocolumn, the SLR formed by the coupling of the silicon nanocolumn Mie resonance and the diffraction wave of the array surface has a greater local field strength, and provides more degrees of freedom for the regulation of the SLR. Therefore, by using the coupling between the Mie resonance of the silicon nanocolumn and the silica nanocolumn, the interference between the two silicon / silica nanocolumns in the silicon / silica nanocolumn dimer, and the diffraction of the periodic array, the local field strength of the SLR can be effectively enhanced, the bandwidth of the SLR can be narrowed, and the sensing sensitivity and the quality factor can be enhanced.

[0049] The above specific embodiments further illustrate the technical problems solved by the application, the technical solutions and the beneficial effects. It should be understood that the above description is only for specific embodiments of the application and is not intended to limit the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A surface lattice resonance based optical sensor, characterized in that, it comprises a substrate (1) and a silicon / silica nanocolumn dimer array on the substrate (1); wherein, the silicon / silica nanocolumn dimer array is periodically and uniformly arranged by silicon / silica nanocolumn dimers; the silicon / silica nanocolumn dimer comprises two silicon / silica nanocolumns arranged at intervals; the silicon / silica nanocolumn comprises a silicon nanocolumn (2) and a silica nanocolumn (3) arranged in turn from top to bottom.

2. The surface lattice resonance based optical sensor according to claim 1, characterized in that, the diameter of the silicon nanocolumn (2) and the silica nanocolumn (3) in the same silicon / silica nanocolumn is the same; the silicon nanocolumn (2) and the silica nanocolumn (3) in the same silicon / silica nanocolumn are completely coincident in the up-down direction.

3. The surface lattice resonance based optical sensor according to claim 2, characterized in that, the diameter of the silicon / silica nanocolumn is 60-300 nm.

4. The surface lattice resonance based optical sensor according to claim 1, characterized in that, the height H1 of the silicon nanocolumn (2) is 50-300 nm; the height H2 of the silica nanocolumn (3) is 100-900 nm.

5. The surface lattice resonance based optical sensor according to claim 1, characterized in that, the silicon / silica nanocolumn dimer array is uniformly arranged by silicon / silica nanocolumn dimers in the X direction and the Y direction with the same period P.

6. The surface lattice resonance based optical sensor according to claim 5, characterized in that, the period P is 300-1000 nm.

7. The surface lattice resonance based optical sensor according to claim 1, characterized in that, the center distance L between the two silicon / silica nanocolumns in the silicon / silica nanocolumn dimer is 70-400 nm.

8. The surface lattice resonance based optical sensor according to claim 1, characterized in that, the material of the substrate (1) is glass or quartz.

9. A testing method for the surface lattice resonance based optical sensor according to any one of claims 1-8, characterized in that, the method steps comprise: a calculation transmission spectrum step, which comprises: using the finite difference time domain method to simulate and calculate, first constructing a physical model of a periodic unit in the surface lattice resonance based optical sensor, setting a perfect matched layer on the upper and lower boundaries and a periodic boundary condition on the four surrounding boundaries, setting a vertical incident plane wave on the upper surface, and calculating the transmission spectrum of the corresponding physical model; wherein the transmission valley in the transmission spectrum corresponds to the surface lattice resonance; changing the environmental refractive index, and according to the calculation transmission spectrum step, calculating different transmission spectra corresponding to different environmental refractive indices. According to different transmission spectra corresponding to different environmental refractive indexes, surface lattice resonance wavelengths under different environmental refractive indexes are obtained, a change amount of the surface lattice resonance wavelength caused by a unit refractive index is calculated, and a sensitivity of the optical sensor based on the surface lattice resonance is obtained; According to a surface lattice resonance bandwidth obtained from the transmission spectrum, the sensitivity is divided by the surface lattice resonance bandwidth, and a quality factor of the optical sensor based on the surface lattice resonance is obtained.

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