Optical biosensor based on cascaded semi-buried high-contrast grating

Abstract

The invention relates to the technical field of micro-nano optical devices, and discloses an optical biosensor based on a cascaded semi-buried high-contrast grating, which comprises an upper grating structure, a lower grating structure and a detection substance channel, each of the upper grating structure and the lower grating structure is composed of a substrate layer, a waveguide layer and a high-contrast grating layer embedded in the waveguide layer; a gap formed between the upper-layer grating structure and the lower-layer grating structure forms a detection substance channel; the grating layers are periodically distributed; and the waveguide layer and the grating layer are in direct contact with the detection substance channel. Different from a traditional composite grating, the cross section of the grating is rectangular, the grating is simple in structure, good in robustness and convenient to prepare, and different modes can be flexibly regulated and controlled by changing structural parameters of the cascaded semi-buried grating.

Description

Technical Field

[0001] The patent of this invention relates to the field of micro-nano optical device technology, specifically an optical biosensor based on cascaded semi-buried high-contrast gratings. Background Art

[0002] Optical sensors are widely used in the field of biosensing due to their high sensitivity, high precision and excellent anti-electromagnetic interference performance, including surface plasmon resonance, fiber Bragg grating and high contrast grating (HCG). The surface plasmon resonance structure has attracted widespread attention due to its extremely high sensitivity, but the high loss and instability of metal materials limit its application in complex scenarios. The traditional micro-nano grating structure has the problem of mutual restriction between sensitivity and quality factor. To obtain high sensitivity, more light field must be leaked into the substance to be measured; and in order to maintain a high quality factor, the light field needs to be bound in the grating. HCG has the characteristics of compact size, simple structure and rapid response. Introducing bound states in the continuum (BICs) in this structure can improve sensitivity and quality factor at the same time, optimizing the trade-off between performance indicators.

[0003] BICs are a special type of wave mode that is within the continuum range but can still maintain a special state of local non-radiation. Due to the lack of radiation loss, the BICs mode has a Q factor approaching infinity. Although it does not affect the sensitivity of the sensor device, the lack of loss leads to the absence of resonance peaks. When a perturbation is introduced to slightly destroy the original symmetry, BICs will evolve into quasi-BICs. Quasi-BICs have less radiation and produce narrow-band high-Q-factor resonance peaks. Currently, BICs have been applied in nonlinear enhancement, laser and sensing research, and have shown advantages in manipulating light fields and modulating light-matter interactions. Summary of the invention

[0004] Based on the current research status of optical sensors and the advantages of high-contrast gratings, the present invention proposes an optical biosensor based on cascaded semi-buried high-contrast gratings. The sensor has a simple structure, good robustness and is easy to prepare. By changing the structural parameters of the cascaded semi-buried gratings, flexible regulation of different modes is achieved.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] An optical biosensor based on cascaded semi-buried high-contrast gratings comprises: an upper grating structure, a lower grating structure and a detection material channel; the upper grating structure and the lower grating structure are both composed of a substrate layer, a waveguide layer, and a high-contrast grating layer buried in the waveguide layer; the gap formed between the upper and lower grating structures constitutes the detection material channel; the grating layer presents a periodic distribution; the waveguide layer and the grating layer are in direct contact with the detection material channel.

[0007] Furthermore, the grating layer is made of a high refractive index material such as Si, GaAs or SiN.

[0008] Furthermore, the waveguide layer is made of a low refractive index material, such as BCB or SiO2.

[0009] Furthermore, the substrate layer is made of a high-refractive material, Si.

[0010] Furthermore, the detection material channel is filled with test objects with different refractive indices.

[0011] Furthermore, the micro-nano grating is semi-buried in the waveguide layer by combining deep ultraviolet lithography and dry etching.

[0012] Furthermore, the optical biosensor achieves regulation of different modes by adjusting the incident angle and optimizing the structural parameters of the grating. Regulation of the incident angle ensures the coexistence of multiple peaks, thereby achieving multi-channel sensing. Adjustment of the structural parameters can maintain different modes in a high Q state.

[0013] Furthermore, the optical biosensor has good robustness. Even if there is a certain deviation in the positions of the upper and lower gratings during the manufacturing or operation process, the sensor can still maintain a stable working state without significantly affecting its accuracy and performance.

[0014] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: the optical biosensor based on cascaded semi-buried high-contrast grating provided by the present invention is mainly composed of two substrate layers, two waveguide layers, two high-contrast grating layers and a detection material channel. The structure is simple and easy to process. By changing the incident angle, a high-Q narrowband resonance mode can be obtained to achieve a three-peak resonance phenomenon, thereby realizing multi-channel sensing. The second resonance peak and the third resonance peak belong to a resonance mode, and the distance between the central wavelengths is the same under fixed structural parameters, so that a self-calibration function can be realized. By changing the width of the grating or the depth of embedding, the conversion between different types of BICs can also be achieved, so that different modes are maintained in a high-Q state. The sensor is composed of all-dielectric materials, and while having high sensitivity, it can also obtain a high Q factor. It has certain guiding significance and good application prospects in the field of micro-nano optical sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. 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 creative labor.

[0016] Figure 1 A schematic structural diagram of an optical biosensor based on cascaded semi-buried high-contrast grating provided in an embodiment of the present invention;

[0017] Figure 2 A reflection spectrum diagram of three resonance peaks of an optical biosensor based on a cascaded semi-buried high-contrast grating provided in an embodiment of the present invention when the incident angle of the incident light changes;

[0018] Figure 3 A reflectance spectrum diagram of three resonance peaks of an optical biosensor based on a cascaded semi-buried high-contrast grating provided in an embodiment of the present invention when the incident angle is 3° and changes with Δw;

[0019] Figure 4 A reflection spectrum diagram of three resonance peaks of an optical biosensor based on a cascaded semi-buried high-contrast grating provided in an embodiment of the present invention when the incident angle is 3° and the displacement L changes;

[0020] FIG5 is a reflection spectrum of three resonance peaks of an optical biosensor based on a cascaded semi-buried high-contrast grating provided by an embodiment of the present invention when the refractive index of the substance to be tested changes;

[0021] Explanation of the reference numerals: 1. base layer; 2. waveguide layer; 3. detection material channel; 41. upper grating layer; 42. lower grating layer; 5. periodic unit. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] like Figure 1As shown, the optical biosensor based on the cascaded semi-buried high-contrast grating structure provided by the embodiment of the present invention includes: a substrate layer 1, a waveguide layer 2, a detection material channel 3, a grating layer 4 and a plurality of periodic units 5, each periodic unit 5 is composed of an upper high-contrast grating 41 and a lower high-contrast grating 42, a waveguide layer 2 and a substrate layer 1, and the grating 4 is in contact with the detection material channel 3, and its grating cross section is rectangular. By changing the incident angle, three high-Q narrow-band resonance peaks can be obtained, thereby realizing multi-channel sensing. The second resonance peak and the third resonance peak belong to a resonance mode, and the distance of the central wavelength is the same under fixed structural parameters, and a self-calibration function can be realized. By changing the width of the grating or the depth of embedding, the conversion between different types of BICs can be realized, so that different modes are maintained in a high-Q state.

[0025] The micro-nano grating is semi-buried into the waveguide layer 2 by combining deep ultraviolet lithography and dry etching.

[0026] In the embodiment of the present invention, the grating layer 4 is arranged on the upper and lower sides of the detection material channel 3. The structure of the present invention has good robustness, and the two layers of high contrast gratings can also be in an asymmetric state. The optical biosensor realizes volume refractive index sensing by changing the refractive index of the detection material channel 3.

[0027] In the embodiment of the present invention, the base layer 1 is made of silicon (Si) with a refractive index of 3.48, the waveguide layer 2 is made of silicon dioxide (SiO2) with a refractive index of 1.48, the detection material channel 3 uses a solution with a refractive index of 1.311~1.319 as the test liquid, and the grating layer 4 is silicon (Si) with a refractive index of 3.48.

[0028] like Figure 1 As shown, in the embodiment of the present invention, the initial structural parameters are set as follows: grating height h = 800 nm, width w = w1 = w2 = 250 nm, depth of grating buried in waveguide layer t = 150 nm, offset of lower grating relative to upper grating L = 0 nm, waveguide layer thickness hp = 500 nm, detection material channel height hq = 2700 nm, substrate layer thickness H = 2000 nm, incident angle α is -3°~ 3°. One period includes upper and lower rectangular grating structures, waveguide layer, substrate layer and detection material channel in the middle. The gratings are periodically arranged in the xz plane, the periodic unit is 820 nm, infinitely long in the y direction, and TE wave is incident.

[0029] In this embodiment, Figure 2The reflectance spectra of the three resonance peaks of the optical biosensor are shown when the width of the upper and lower grating layers is w = 250 nm within one cycle. The incident angle α is -3°~3°. When the incident angle α approaches 0°, the first resonance peak redshifts and the full width at half maximum (FWHM) does not change significantly, and it is always in an extremely narrow high-Q state; the second and third resonance peaks blueshift and the FWHM gradually decreases to 0, and both appear as SP-BICs when α = 0°.

[0030] In this embodiment, Figure 3 The transmission spectrum of the optical biosensor with the change of Δw is shown when the incident angle of the incident light is α = 3°, the grating width w1 = w + Δw, w2 = w- Δw. When Δw is zero, the three resonance peaks are in an extremely narrow state. As Δw increases, the FWHM of the first and second resonance peaks first decrease and then increase, reaching accidental BICs at Δw = 4 nm and 2 nm, respectively. That is, when the symmetry of the second resonance peak is broken, SP-BICs becomes quasi-BICs. At this time, by optimizing Δw, the loss of Q factor can be compensated to make it return to BICs. The multi-parameter tunability of the second resonance peak increases the flexibility of the structure.

[0031] In this embodiment, Figure 4 The reflection spectrum of the optical biosensor with different displacement differences L is shown when the incident light α = 3°, the refractive index of the test liquid in the detection material channel is 1.311, and other parameters remain unchanged. As L increases, the transmission of the three resonance peaks does not change significantly. That is, the optical biosensor has good robustness to the alignment of the grating. Even if there is a slight deviation in the position of the grating during manufacturing or operation, the sensor can still maintain a stable working state without significantly affecting its accuracy and performance.

[0032] In this embodiment, Figure 5The transmission spectra of the three resonance peaks of the optical biosensor under different refractive index environments are shown when the incident angle α = 3°, the grating width w = 250 nm, Δw = 0 nm, and L = 0 nm. The refractive indices of the test liquid in the detection material channel are 1.311, 1.313, 1.315, 1.317, and 1.319, respectively. The change in the refractive index of the test liquid will cause the drift of the central wavelength of the sensor output spectrum, thereby realizing optical volume refractive index sensing. The calculated sensitivities of the three resonance peaks are 463.29 nm / RIU, 176.66 nm / RIU, and 180.18 nm / RIU, respectively, and the quality factors are 40611.32, 21304.41, and 22367.86, respectively. The displacement between the central wavelengths of the second resonance peak and the third resonance peak remains unchanged, which can realize the self-calibration function.

[0033] The present invention provides an optical biosensor based on an all-medium structure, the main feature of which is the use of a cascaded semi-buried high-contrast grating structure. The grating is semi-buried in the waveguide layer to enhance the interaction between the light field and the substance to be measured. By utilizing its multiple high Q-factor resonance peaks that can be adjusted by multiple parameters, multi-channel sensing and self-calibration functions are successfully realized, thereby greatly improving the comprehensive performance of the sensor and bringing innovative possibilities for a variety of detection applications. By destroying the vertical incident angle, the second resonance peak evolves from SP-BIC to quasi-BIC, and then further changes the grating width to compensate for the lost Q factor so that it evolves from quasi-BIC to BIC again, realizing the function of multi-parameter control of BIC. In the present invention, by reasonably designing the width, height, embedding depth, incident light angle and other structural parameters of the grating in the periodic unit, multi-peak BIC resonance is realized to solve the problem of mutual restriction between S and Q factors in traditional grating sensors, and to realize the detection of gases, liquids and other substances to be measured with different refractive indices, playing an important role in the fields of chemistry, medicine, integrated optics, etc.

[0034] In summary, the technical advantages of the optical biosensor based on cascaded semi-buried high-contrast grating provided by the present invention are embodied in the following aspects: (1) The all-dielectric structure of the present invention ensures the lossless nature of the sensor, makes the structure more concise and guarantees a longer service life; (2) The novel cascaded grating structure of the present invention semi-buries the grating in the waveguide layer, which can enhance the interaction between the light field and the substance to be measured and enhance the sensitivity of the sensor. (3) The Q factor of the resonance peak is improved by changing the incident angle to excite the quasi-BIC, and it also has a self-calibration function. This design realizes flexible control and the three resonance peaks broaden the biological detection range; (4) The optical biosensor of the present invention can compensate for the lost Q factor by adjusting the asymmetric parameters of the grating width, realize the conversion of different types of BICs, and maintain different resonance peaks in a high Q state. (5) The optical biosensor of the present invention has good robustness in the degree of alignment of the grating. (6) The optical biosensor of the present invention The optical sensor of the present invention realizes liquid or gas refractive index sensing by changing the refractive index change of the substance to be measured.

[0035] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An optical biosensor based on cascaded semi-buried high-contrast gratings, characterized in that: The sensor structure includes an upper grating structure, a lower grating structure and a detection material channel; the upper grating structure and the lower grating structure are both composed of a substrate layer, a waveguide layer, and a high-contrast grating layer buried in the waveguide layer; the gap formed by the upper and lower grating structures constitutes the detection material channel; the grating layer is periodically distributed; the waveguide layer and the grating layer are in direct contact with the detection material channel.

2. The optical biosensor based on cascaded semi-buried high-contrast grating according to claim 1, characterized in that: The grating layer is made of a high refractive index material, such as Si (silicon), GaAs (gallium arsenide) or SiN (silicon nitride).

3. The optical biosensor based on cascaded semi-buried high-contrast grating according to claim 1, characterized in that: The waveguide layer is made of a low refractive index material, such as SiO2 (silicon dioxide) or BCB (benzocyclobutene).

4. The optical biosensor based on cascaded semi-buried high-contrast grating according to claim 1, characterized in that: The base layer is made of a high refractive index material, Si (silicon).

5. The optical biosensor based on cascaded semi-buried high-contrast grating according to claim 1, characterized in that: The detection material channel is filled with test objects with different refractive indices.

6. The optical biosensor based on cascaded semi-buried high-contrast grating according to claim 1, characterized in that: The micro-nano grating is embedded in the waveguide layer at a controllable depth by combining deep ultraviolet lithography and dry etching.

7. The optical biosensor based on cascaded semi-buried high-contrast grating according to claim 1, characterized in that: The optical sensor can achieve multi-peak high Q factor characteristics by adjusting the incident angle, and can achieve regulation of different modes by changing the width of the grating.

8. The optical biosensor based on cascaded semi-buried high-contrast grating according to claim 1, characterized in that: The optical biosensor has good robustness in the degree of alignment of the upper and lower gratings. Even if there is a certain deviation in the positions of the upper and lower gratings during manufacturing or operation, the sensor can still maintain a stable working state without significantly affecting its accuracy and performance.

Images