CN113376122A

CN113376122A - All-dielectric super-surface refractive index sensor based on four-rectangular silicon pillar structure

Info

Publication number: CN113376122A
Application number: CN202110645693.XA
Authority: CN
Inventors: 高子昂; 余世林; 赵同刚
Original assignee: Beijing University of Posts and Telecommunications
Current assignee: Beijing University of Posts and Telecommunications
Priority date: 2021-06-01
Filing date: 2021-06-01
Publication date: 2021-09-10

Abstract

The invention discloses an all-dielectric super-surface refractive index sensor based on a four-rectangular silicon pillar structure, which mainly comprises a dielectric substrate and a silicon super-surface microstructure unit array, wherein the silicon super-surface microstructure unit array comprises a plurality of microstructure units: each microstructure unit is composed of four identical rectangular silicon columns, and the rectangular silicon columns are distributed in a centrosymmetric mode. The invention has no metal structure and ohmic loss, can be used for detecting gas and liquid with different refractive indexes, and has higher sensitivity and quality factor. In addition, the invention is based on silicon materials, has CMOS compatibility and is expected to realize large-scale integrated production.

Description

All-dielectric super-surface refractive index sensor based on four-rectangular silicon pillar structure

Technical Field

The invention relates to the field of optical refractive index sensing, in particular to an all-dielectric super-surface refractive index sensor based on a four-rectangular silicon pillar structure.

Background

Optical refractive index sensors are widely used for refractive index measurement in physicochemical, biomedical, food processing, and other fields, and have attracted much attention from researchers. In general, the sensitivity of a refractive index sensor is defined as the resonant wavelength change per unit refractive index, i.e.: s ═ Δ λ/Δ n, and the figure of merit is the ratio of sensitivity to full width at half maximum (FOM ═ S/FWHM). The research on refractive index sensors is mainly focused on metal-based plasmonic structures and dielectric-based structures, however, the quality factor of the metal structure is generally low due to strong radiation loss caused by free electron oscillation in the metal structure, which limits the application of metal-based plasmonic structure devices in nanophotonics. And some dielectric-based structures such as fiber grating structures, photonic crystal cavities and whispering gallery mode resonators, etc. These structures have low loss, relatively high quality factor, but relatively low sensitivity and some of them are bulky, which does not meet the requirements for further miniaturization and integration of the device.

Recently, all-dielectric super-surface refractive index sensors based on high refractive index materials (silicon, germanium) have received much attention from researchers. The super surface is a two-dimensional metamaterial structure composed of periodically arranged super atoms. Compared with other structures, the all-dielectric super-surface resonant cavity structure made of the high-refractive-index material has the following important characteristics: 1. the loss is small, and the ultrahigh quality factor and the great local field enhancement can be realized. 2. The optical field is mainly bound inside the device, and is beneficial to enhancing the interaction between light and substances inside the material. 3. Compatible with CMOS process, low manufacturing cost and hopeful of realizing large-scale integrated production. Meanwhile, Fano resonance, as a sharp asymmetric spectral line, is proven to be realized in all-dielectric meta-surfaces with high refractive index. The extremely narrow line width formed by Fano resonance in the all-dielectric super-surface is close to the modulation depth of 100%, and the performance of the refractive index sensor can be further improved by extremely large local field enhancement.

In summary, based on the shortages of the current optical refractive index research and the advantages of the all-dielectric super-surface of the high-refractive index material, the inventor proposes an all-dielectric super-surface refractive index sensor based on a four-rectangular silicon pillar structure.

Disclosure of Invention

The invention provides an all-dielectric super-surface refractive index sensor based on a four-rectangular silicon column structure, which consists of a dielectric substrate and a silicon super-surface microstructure unit array, has higher sensitivity and quality factor, meets the measurement requirement in practical application, and is specifically described as follows:

the all-dielectric super-surface refractive index sensor based on the four-rectangular silicon pillar structure comprises a dielectric substrate and a silicon super-surface microstructure unit array from bottom to top, wherein the silicon dielectric super-surface microstructure unit array comprises a plurality of microstructure units: each silicon medium super-surface micro unit is composed of four identical rectangular silicon columns, and the rectangular silicon columns are distributed in a centrosymmetric mode.

In the concrete implementation, the substrate material is silicon dioxide, and the silicon medium super-surface structure material is kept unchanged.

Particularly, the thickness of the super surface of the silicon medium is 250 nm-360 nm.

Further, the cross section of the rectangular silicon column is square, and the side length is 220 nanometers.

In specific implementation, the all-dielectric super-surface optical refractive index sensor structure works in any wave band of infrared wave bands.

The technical scheme provided by the invention has the beneficial effects that:

1. the all-dielectric super-surface optical refractive index sensor provided by the invention has higher sensitivity and quality factor, and meets the measurement requirement in practical application;

2. the refractive index sensor can be applied to the related fields of gas, liquid, biological sensing and the like, and can bring great convenience to industrial experimental measurement.

3. The invention is compatible with CMOS technology, has low manufacturing cost and is expected to realize large-scale integrated production.

Drawings

Fig. 1 is a schematic structural diagram of an all-dielectric super-surface refractive index sensor based on a four-rectangular silicon pillar structure, which includes a top view of an overall structure, a top view of a structural unit, and a side view.

Fig. 2 is a response characteristic of the optical refractive index sensor under different refractive indexes of media to be measured according to an embodiment example.

Fig. 3 is a graph illustrating the variation of the detected peak or valley values of the media with different refractive indexes.

Detailed Description

The following detailed description of embodiments of the invention is provided in conjunction with the accompanying drawings: the present embodiment is premised on the all-dielectric super-surface refractive index sensor based on the four-rectangular silicon pillar structure, and the scope of the present invention includes but is not limited to this embodiment.

As shown in fig. 1, there is an example of an all-dielectric super-surface refractive index sensor based on a four-rectangular silicon pillar structure, which includes a super-surface structure and a transparent silicon dioxide structure substrate. The structural unit composed of four rectangular silicon nano-columns is arranged on a transparent substrate and made of monocrystalline silicon, wherein the period in the XY direction is 660nm, the thickness t of each square silicon dielectric column is 300nm, the cross section of each square silicon dielectric column is square, the side length is 220nm, the four square silicon dielectric columns are arranged in a centrosymmetric mode, and the interval between every two square silicon columns is 55 nm. The operating wavelength of this example is between 1000nm and 1300 nm.

The refractive index of the silicon dioxide substrate used by the sensor of the embodiment is 1.5, and the whole manufacturing process comprises the following steps: 1. crystalline silicon is deposited to a thickness of 300nm on a clean silicon dioxide substrate. 2. And uniformly coating electron beam photoresist with proper thickness on the deposited silicon surface, and making a corresponding periodic pattern by using an electron beam exposure process. 3. Subsequently, development and fixing are performed. 4. Reactive ion etching is performed on the exposed silicon portion. 5. And removing the residual electron beam photoresist by using oxygen ions to obtain the required super-surface light refractive index sensor structure.

Fig. 2 shows a transmission spectrum of the sensor example in different refractive index environments, the refractive indexes of corresponding detection substances are respectively 1, 1.01, 1.02, 1.03 and 1.04, when a material to be detected is filled in the super-surface structure to change, the effective refractive index of the structure also changes, so that the position of a resonance peak is correspondingly changed, and therefore, the change of the refractive index can be obtained through the change of the resonance wavelength, and the sensing detection of the refractive index of the substance to be detected is completed. The two resonances in fig. 2 are called Mode1 and Mode2, respectively, and the red shift phenomenon in the figure verifies this principle.

The sensitivity of the sensing device is S ═ delta lambda/delta n, wherein delta lambda is the change of the Fano resonance wavelength, and delta n is the change of the refractive index of the medium. Fig. 3 shows the relationship between the resonant wavelength of the refractive index sensor and media with different refractive indexes, where λ is the resonant wavelength of the resonant mode, and n is the refractive index of the medium to be measured. The calculated sensitivity of the refractive index sensor corresponding to the three resonance modes is S (Mode1) ═ 245nm/RIU, and S (Mode2) ═ 320nm/RIU, respectively. The calculated FOM values are: FOM (Mode1) ═ 27.2, FOM (Mode2) ═ 8.

The invention is a high-performance all-dielectric sensing device, can realize the detection of substances to be detected such as gas and liquid with different refractive indexes, and can play an important role in the fields of chemistry, medical treatment, integrated optics and the like.

Claims

1. The all-dielectric super-surface refractive index sensor based on the four-rectangular silicon pillar structure is characterized in that the optical refractive index sensor mainly comprises a dielectric substrate and a silicon super-surface microstructure unit array, wherein the silicon dielectric super-surface microstructure unit array comprises a plurality of microstructure units: each silicon medium super-surface micro unit is composed of four identical rectangular silicon columns, and the rectangular silicon columns are distributed in a centrosymmetric mode.

2. The all-dielectric super-surface refractive index sensor based on the four-rectangular silicon pillar structure as claimed in claim 1, wherein the dielectric substrate material is silicon dioxide, and the silicon dielectric super-surface structure material is unchanged.

3. The all-dielectric super-surface refractive index sensor based on the four-rectangular silicon pillar structure as claimed in claim 1, wherein the thickness of the silicon dielectric super-surface structure is 250 nm-360 nm.

4. The all-dielectric super-surface refractive index sensor based on the four-rectangular silicon pillar structure as claimed in claims 1-3, wherein the all-dielectric super-surface optical refractive index sensor structure operates in any one of infrared bands.