Optical waveguide device and optical structure thereof

Abstract

The utility model provides an optical waveguide device and an optical structure thereof, the optical structure comprises a first metal thin film layer, a dielectric layer and a second metal thin film layer which are sequentially arranged along a light incidence direction, a first nano-structure array is arranged in the first metal thin film layer, and the outer side surface of the second metal thin film layer is smooth and uniform; the first nano-structure array is embedded into or penetrates through the first metal thin film layer, and the duty ratio is greater than 50%; the duty ratio is a first ratio of the length of a non-influence region in the one-dimensional first nanostructure array to the total length of the first nanostructure, or is a second ratio of the area of the non-influence region in the two-dimensional first nanostructure to the total area of the first nanostructure array; and the optical structure couples incident light with a preset light frequency to the surface wave propagating along the outer side surface of the second metal film layer. According to the optical structure, the environmental interference resistance of the device can be effectively improved, low-concentration biomolecules can be detected, and the stability and repeatability of biomolecule detection are improved.

Description

Technical Field

[0001] The present disclosure relates to the field of optical technology, and in particular to an optical waveguide device and an optical structure thereof. Background Art

[0002] Surface Plasmon Polariton (SPP) is a surface wave formed by the coupling of metal surface charges and light fields. The resonance conditions of this surface wave, such as wavelength, intensity, and angle of incidence, vary with the refractive index of the environment in which it is located. Therefore, Surface Plasmon Resonance (SPR) is used to measure the refractive index of the environment and is widely used and studied in the field of biomolecular sensing.

[0003] How to combine SPR with optical waveguide devices (such as optical fiber) so as to use optical fiber waveguide technology to conveniently stimulate SPR and perform sensing is a topic that people have been studying. The SPR microcavity composed of nanowire groove arrays on metal films and the sensor device formed by its integration on the end face of single-mode optical fiber are currently the fiber end plasmon sensing technologies with the highest sensing signal-to-noise ratio. This microcavity can be composed of an SPP grating coupling region in the middle and an SPP reflection region next to it, or it can be composed of a periodic structure and an embedded defect structure, and it can also be coupled with other three-dimensional structures to further improve the sensing sensitivity. The integrated device of the above two-dimensional or three-dimensional structure and the end face of a single-mode optical fiber has achieved 10 in refractive index sensing experiments. -7 ~10 -6 Noise equivalent detection at the RIU level.

[0004] However, for biomolecule sensing applications, it is not enough for the optical structure to have sufficient sensitivity. Another key aspect is that interference from the environment or unwanted processes must be eliminated to accurately extract the signal of the target analyte. From the perspective of physical devices, this requirement requires a simple and controllable physical interface to accommodate the binding and dissociation processes of biomolecules. To achieve this goal, the most direct choice is to use the smooth and uniform surface of an unstructured metal film as the surface of the SPR sensor. However, the plasmon microcavity structures on the end faces of the above-mentioned optical fibers all have surface nanostructures, which may lead to complex interface processes, making them susceptible to interference, difficult to detect low-concentration samples, and unable to meet the actual sensing detection needs. Utility Model Content

[0005] The present invention aims to design a solution to provide a micro-nano optical structure of an optical fiber end face with a smooth metal surface based on a metal thin film nanowire groove array SPR microcavity, and provides an optical waveguide device and its optical structure to overcome the defects of the optical structure in the optical waveguide end face SPR sensor device in the prior art, which is generally susceptible to interference, difficult to detect low-concentration samples, and unable to meet actual sensing detection needs.

[0006] The present invention solves the above technical problems through the following technical solutions:

[0007] In a first aspect of the present disclosure, an optical structure is provided, characterized in that the optical structure comprises a first metal film layer, a dielectric layer, and a second metal film layer sequentially arranged along a light incident direction, wherein the first metal film layer, the dielectric layer, and the second metal film layer form a MIM (metal-dielectric-metal) film layer;

[0008] The first metal film layer is provided with a first nanostructure array, and the outer side surface of the second metal film layer is smooth and uniform;

[0009] The first nanostructure array is embedded in or penetrates the first metal film layer;

[0010] The duty cycle of the first nanostructure array is greater than 50%;

[0011] The duty cycle is a first ratio of a length of a non-affected region in the first nanostructure array in one dimension to a total length of the first nanostructure, or a second ratio of an area of ​​the non-affected region in the first nanostructure in two dimensions to a total area of ​​the first nanostructure array;

[0012] The optical structure is used to couple incident light of a preset optical frequency to a surface wave propagating along the outer side surface of the second metal film layer.

[0013] Preferably, the optical structure is used to couple the incident light of the preset optical frequency to the light wave propagating along the MIM waveguide dielectric layer and the surface wave propagating along the outer side surface of the second metal film layer;

[0014] The MIM waveguide is formed in the MIM film layer; the MIM waveguide can mainly limit the light wave of the preset light frequency to be transmitted in the dielectric layer of the MIM waveguide along the plane of the MIM film layer.

[0015] Preferably, the first evanescent depth of the surface wave is smaller than a preset evanescent depth corresponding to a preset surface plasmon polariton SPP;

[0016] The preset evanescent depth is the evanescent depth of the surface plasmon polaritons SPP along the outer side surface of the second metal film layer at the preset light frequency when assuming that the second metal film layer is infinitely thick.

[0017] Preferably, the first nanostructure array comprises a first periodic structure with a first preset period, and the first preset period is smaller than a preset wavelength corresponding to the surface plasmon polaritons SPP;

[0018] The preset wavelength is the wavelength of the surface plasmon polaritons SPP along the outer side of the second metal film layer at the preset light frequency when the second metal film layer is assumed to be infinitely thick;

[0019] The optical structure is used to couple the incident light of the preset optical frequency whose transmission direction is perpendicular to the MIM film layer or whose angle with the direction perpendicular to the MIM film layer is less than a set value to the surface wave propagating along the outer side of the second metal film layer.

[0020] Preferably, the nanostructure array further comprises a second nanostructure array, wherein the second nanostructure array comprises a second periodic structure with a second preset period;

[0021] Wherein, a MIM waveguide is formed in the MIM thin film layer;

[0022] The second periodic structure surrounds the first periodic structure in a direction along the plane of the MIM film layer and is located at a first preset position in a direction perpendicular to the plane of the MIM film layer;

[0023] Under the preset optical frequency, the second periodic structure reflects the light waves transmitted along the MIM waveguide dielectric layer, and confines the light waves transmitted along the MIM waveguide dielectric layer in the direction along the plane of the MIM thin film layer within and near the space surrounded by the second periodic structure, thereby forming a photonic crystal microcavity of the MIM waveguide.

[0024] Preferably, the second periodic structure is embedded in or penetrates the first metal film layer, and the second preset period is smaller than the first preset period.

[0025] Preferably, the first periodic structure and / or the second periodic structure is a structure with a complete periodic arrangement, or a structure after the complete periodic arrangement is adjusted within a first preset range.

[0026] Preferably, the nanostructure array further comprises a third nanostructure array, and the third nanostructure array comprises a single or multiple defect structures;

[0027] Wherein, a MIM waveguide is formed in the MIM thin film layer;

[0028] The defect structure is inserted into the first periodic structure in a direction along the plane of the MIM film layer, and is located at a second preset position in a direction perpendicular to the plane of the MIM film layer;

[0029] At the preset optical frequency, in the direction along the plane of the MIM thin film layer, the light wave transmitted along the MIM waveguide dielectric layer is confined near the defect structure, forming a defect state photonic crystal microcavity of the MIM waveguide.

[0030] Preferably, the defect structure is a non-periodic nanostructure embedded in or penetrating the first metal film layer and inserted into the first periodic structure, or a periodic nanostructure different from the first periodic structure.

[0031] Preferably, the first periodic structure is a structure with a complete periodic arrangement, or a structure after the structure with a complete periodic arrangement is adjusted within a second preset range.

[0032] Preferably, the thickness of the dielectric layer is less than a preset thickness;

[0033] The calculation formula of the preset thickness is: the preset thickness=(the wavelength of light in vacuum corresponding to the preset light frequency / the refractive index of the dielectric layer)×0.5.

[0034] Preferably, the nanostructure array is a nanowire groove structure array.

[0035] Preferably, the second metal film layer does not contain a nanostructure array.

[0036] Preferably, part or all of the nanostructure array penetrates the first metal film layer;

[0037] The penetrating nanostructure is filled with a dielectric material, no adhesion layer is provided between the dielectric layer and the first metal film layer, and an adhesion layer is provided between the dielectric layer and the second metal film layer.

[0038] Preferably, the duty cycle of the first nanostructure array is greater than 70%.

[0039] Preferably, a detection layer for sensing preset environmental parameters is provided on or near the outer side surface of the second metal film layer, and the detection layer is used for sensing and detecting by measuring reflected light from the optical structure.

[0040] Preferably, the detection layer includes at least one of the following:

[0041] A detection layer for responding to molecular adsorption, a detection layer for responding to temperature, a detection layer for responding to pressure, and a detection layer for responding to an acoustic field.

[0042] In a second aspect of the present disclosure, there is also provided an optical waveguide device, the optical waveguide device comprising an optical waveguide body and the optical structure as described above;

[0043] The incident light irradiates the optical structure via the optical waveguide body, and the reflected light returns via the same optical waveguide body;

[0044] The side of the optical structure away from the second metal film layer is bonded to the end plane of the optical waveguide body, and the part of the optical structure constituting the MIM waveguide photonic crystal microcavity is aligned with the waveguide core in the optical waveguide body.

[0045] Preferably, the optical waveguide body is a single-mode optical fiber, and the angle between the MIM film layer in the optical structure and the axis of the single-mode optical fiber is within a preset angle range.

[0046] Preferably, the preset angle range is 80° to 90°.

[0047] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present disclosure.

[0048] The positive and progressive effects of this disclosure are:

[0049] In the present disclosure, by providing a first nanostructure array in the first metal film layer, and the duty cycle of the first nanostructure array is greater than 50%, the evanescent depth of the surface wave can be significantly shortened based on the hybridization effect of the MIM waveguide and the SPP on the outer side of the second metal film layer, so as to effectively improve the anti-environmental interference ability of the optical structure without affecting the surface sensitivity; at the same time, by designing the outer surface of the optical structure to be a smooth and uniform surface, it has high detection stability and anti-interference ability during the biomolecule adsorption process, ensuring the feasibility, detection range and accuracy of low-concentration biomolecule detection, improving the stability and repeatability of biomolecule detection, and enabling the optical structure to adapt to a wider range of detection scenarios;

[0050] In addition, by designing a nanostructure array to partially or completely penetrate the first metal film layer and filling the penetrated nanostructure with dielectric material, instead of setting an adhesion layer between the dielectric layer and the first metal film layer, the effect of reducing the ohmic loss of the MIM waveguide while making the optical structure stable is achieved, thereby ensuring the high sensing sensitivity and high stability of the optical waveguide device. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a module schematic diagram of the optical structure of Embodiment 1 of the present disclosure;

[0052] Figure 2It is a first structural schematic diagram of the optical structure of Embodiment 1 of the present disclosure;

[0053] Figure 3 is a second structural schematic diagram of the optical structure of Embodiment 1 of the present disclosure;

[0054] Figure 4 is a third structural schematic diagram of the optical structure of Embodiment 1 of the present disclosure;

[0055] Figure 5 It is a schematic diagram of two-dimensional electromagnetic field simulation for an optical structure in Embodiment 1 of the present disclosure;

[0056] Figure 6 It is a schematic diagram of reflection spectrum simulation for an optical structure in Embodiment 1 of the present disclosure;

[0057] Figure 7 It is a schematic diagram of a module of an optical waveguide device according to Embodiment 2 of the present disclosure;

[0058] Figure 8 It is a schematic structural diagram of an optical waveguide device according to Embodiment 2 of the present disclosure;

[0059] Fig. 9 This is a scanning electron microscope image of a local portion of a MIM waveguide photonic crystal microcavity taken before the optical structure of Example 2 of the present disclosure is transferred to the optical fiber end face;

[0060] Fig.10 This is a schematic diagram of the structure of the biomolecule sensing experimental device of Example 2 of the present disclosure;

[0061] Fig.11 It is a real-time sensing curve diagram of the optical structure of Example 2 of the present disclosure immersed in bio-BSA molecular solutions with different concentrations;

[0062] Fig.12 The real-time sensing curve diagram of the optical structure of Example 2 of the present disclosure is immersed in 100 μg / mL hIgG molecule solution and 100 μg / mL anti-hIgG molecule solution successively, and regenerated and cycled 4 times;

[0063] Fig.13 This is a graph showing the superposition of the real-time sensing curves of the four-cycle regeneration of Example 2 of the present disclosure. DETAILED DESCRIPTION

[0064] The present disclosure is further described below by way of examples, but the present disclosure is not limited to the scope of the examples.

[0065] Example 1

[0066] like Figure 1As shown, this embodiment provides an optical structure (or an optical structure mixed with metal and dielectric), which includes a first metal film layer M1, a dielectric layer I and a second metal film layer M2 arranged in sequence along the light incident direction. The first metal film layer M1, the dielectric layer I and the second metal film layer M2 form a MIM film layer, that is, a metal layer-insulating layer-metal layer, also known as a MIM structure.

[0067] The first metal film layer M1 is provided with a first nanostructure array A1, such as Figure 1 The portion marked in the first metal film layer M1; wherein the first nanostructure array A1 may be the entire nanostructure array or only a portion of the nanostructure array;

[0068] The outer side surface of the second metal film layer M2 is smooth and uniform;

[0069] By setting the sensing surface outside the second metal film layer M2 to be smooth and uniform, the high stability of the data obtained by the sensing detection and the repeatability of the detection operation are guaranteed.

[0070] Specifically, the first metal film layer M1 and the second metal film layer M2 are made of precious metal materials such as gold and silver, and the dielectric layer I is made of materials such as silicon dioxide and silicon nitride. Figure 1 As shown, a protection layer P is further disposed on the first metal film layer M1 , and the protection layer P can be made of materials such as silicon dioxide and silicon nitride.

[0071] The first nanostructure array A1 is embedded in or penetrates the first metal film layer M1;

[0072] The duty cycle of the first nanostructure array A1 is greater than 50%, forming a MIM waveguide; preferably, the duty cycle of the first nanostructure array A1 is greater than 70%.

[0073] In this embodiment, the first metal film layer M1 needs to be as complete as possible, such as the duty cycle of the first nanostructure array A1 is greater than 50% (even greater than 70%), so as to form a MIM waveguide.

[0074] The duty cycle is a first ratio of the length of the non-affected region in the one-dimensional first nanostructure array A1 to the total length of the first nanostructure array A1, or a second ratio of the area of ​​the non-affected region in the two-dimensional first nanostructure array A1 to the total area of ​​the first nanostructure array A1;

[0075] The non-affected area refers to an area where the local structure and material composition do not change with or without the nanostructure, such as a portion of the first metal film layer M1 that is not embedded or penetrated by the nanostructure.

[0076] The optical structure is used to couple incident light of a preset optical frequency to a surface wave propagating along the outer side surface of the second metal film layer M2.

[0077] In one practicable solution, the optical structure is used to couple incident light of a preset optical frequency to light waves propagating along the MIM waveguide dielectric layer and surface waves propagating along the outer side of the second metal film layer M2;

[0078] Wherein, a MIM waveguide is formed in the MIM thin film layer; the MIM waveguide can mainly confine the light wave of a preset optical frequency to be transmitted in the dielectric layer of the MIM waveguide along the direction of the plane of the MIM thin film layer.

[0079] The first evanescent depth of the surface wave is less than a preset evanescent depth corresponding to a preset surface plasmon polariton SPP;

[0080] The preset evanescent depth is the evanescent depth of the surface plasmon polaritons SPP extending outward along the outer side surface of the second metal film layer M2 at a preset light frequency when assuming that the second metal film layer M2 is infinitely thick.

[0081] Specifically, the shorter surface wave evanescent depth makes the optical structure insensitive to changes in the refractive index of the surrounding body, thereby making the optical structure have a strong ability to resist environmental interference (such as temperature changes); at the same time, the optical structure can maintain a high sensitivity to changes in the surface refractive index, thereby having a high sensitivity to the adsorption of biological molecules, and achieving the effect of detecting low concentrations of biological molecules.

[0082] The optical structure is used to be arranged on the end plane of the optical waveguide device to realize the corresponding detection function in the sensing detection scenario. For example, in the biosensing application scenario, the optical structure is placed in a biomolecule solution, and the optical structure receives and reflects the light wave incident vertically from the incident direction (from top to bottom above the first metal film layer M1), and the light wave will be coupled to the surface wave of the second metal film layer M2-solution interface of the lower layer, and the SPR sensing of the molecules adsorbed on the outer surface of the optical structure (i.e., the outer sensing surface) is realized through the surface wave.

[0083] In this scheme, by providing a first nanostructure array A1 in the first metal film layer M1 and designing that the duty cycle of the first nanostructure array A1 is greater than 50%, the evanescent depth of the surface wave can be significantly shortened based on the hybridization effect of the MIM waveguide and the SPP on the outer side of the second metal film layer M2, thereby effectively improving the ability of the optical structure to resist environmental interference without affecting the surface sensitivity; at the same time, by designing the outer surface of the optical structure to be a smooth and uniform surface, it has high detection stability and anti-interference ability during the adsorption process of biological molecules, thereby ensuring the feasibility, detection range and accuracy of low-concentration biological molecules detection, improving the stability and repeatability of biological molecule detection, and enabling the optical structure to adapt to a wider range of detection scenarios.

[0084] In one feasible solution, Figure 2 As shown, the first nanostructure array A1 includes a first periodic structure with a first preset period, and the first preset period is smaller than a preset wavelength corresponding to the surface plasmon polaritons SPP;

[0085] The preset wavelength is the wavelength of the surface plasmon polaritons SPP along the outer side of the second metal film layer M2 at a preset optical frequency when the second metal film layer M2 is assumed to be infinitely thick;

[0086] The optical structure is used to couple incident light of a preset optical frequency whose transmission direction is perpendicular to the MIM film layer or whose angle with the direction perpendicular to the MIM film layer is less than a set value to a surface wave propagating along the outer side of the second metal film layer M2.

[0087] Specifically, the angle with the direction perpendicular to the MIM film layer is less than the set value, indicating that the transmission direction of the incident light is nearly perpendicular to the MIM film layer. The set value can range from 5° to 10°, for example, the transmission direction of the incident light is 85° to the MIM film layer.

[0088] In one feasible solution, Figure 3 As shown, the nanostructure array in this embodiment further includes a second nanostructure array A2, and the second nanostructure array A2 includes a second periodic structure with a second preset period;

[0089] Wherein, a MIM waveguide is formed in the MIM thin film layer;

[0090] The second periodic structure surrounds the first periodic structure in the direction along the plane of the MIM film layer and is located at a first preset position in the direction perpendicular to the plane of the MIM film layer;

[0091] Under a preset optical frequency, the second periodic structure reflects the light waves transmitted along the MIM waveguide dielectric layer, and confines the light waves transmitted along the MIM waveguide dielectric layer to within and near the space surrounded by the second periodic structure in the direction along the plane of the MIM film layer, thereby forming a photonic crystal microcavity of the MIM waveguide.

[0092] Specifically, in an optical waveguide device, the photonic crystal microcavity of the MIM waveguide is located at the end plane of the optical waveguide and aligned with the waveguide core of the optical waveguide. The optical waveguide is located above the first metal film layer M1 and is approximately perpendicular to the metal film. By integrating this photonic crystal microcavity on the end plane of the optical waveguide, the waveguide of the optical waveguide is efficiently coupled to the surface wave at the metal-solution interface.

[0093] In this scheme, the MIM waveguide mode is coupled with the incident light to detect the molecular adsorption process on the outer surface of the optical structure through surface waves.

[0094] In an implementable solution, the second periodic structure is embedded in or penetrates the first metal film layer M1, and the second preset period is smaller than the first preset period.

[0095] Specifically, the second preset period is approximately half of the first preset period; for example, the second preset period is 0.4-0.6, or 0.3-0.7 of the first preset period; of course, it can be redesigned or adjusted according to actual conditions.

[0096] In this scheme, by setting the second preset period to be smaller than the first preset period, it is achieved that under the preset optical frequency, the second periodic structure reflects the light waves transmitted along the MIM waveguide dielectric layer, thereby limiting the light waves transmitted along the MIM waveguide dielectric layer in the direction along the plane of the MIM film layer to the space surrounded by the second periodic structure and the vicinity, thereby forming a photonic crystal microcavity of the MIM waveguide. In this way, it is possible to maintain a high sensitivity to changes in the surface refractive index, thereby having a high sensitivity to the adsorption of biological molecules, and ensuring the feasibility and accuracy of low-concentration biological molecule detection.

[0097] In an implementable solution, the first periodic structure and / or the second periodic structure is a structure with a complete periodic arrangement, or is a structure after the complete periodic arrangement is adjusted within a first preset range.

[0098] Specifically, the first periodic structure and the second periodic structure may be completely periodic structures, or may be structures fine-tuned based on completely periodic structures, that is, they may be flexibly set to meet the setting requirements of more scenarios.

[0099] For example, the first preset range may be to adjust the distance between adjacent units of a completely periodically arranged structure, that is, a structure in which the distances between adjacent units are completely equal, and the adjustment range does not exceed plus or minus 5%, or does not exceed plus or minus 10%.

[0100] In one feasible solution, Figure 4 As shown, the nanostructure array in this embodiment further includes a third nanostructure array A3, and the third nanostructure array A3 includes a single or multiple defect structures;

[0101] Wherein, a MIM waveguide is formed in the MIM thin film layer;

[0102] The defect structure is inserted into the first periodic structure in a direction along the plane of the MIM film layer and is located at a second preset position in a direction perpendicular to the plane of the MIM film layer;

[0103] Under a preset optical frequency, in the direction along the plane of the MIM film layer, the light waves transmitted along the MIM waveguide dielectric layer are confined near the defect structure, forming a defect-state photonic crystal microcavity of the MIM waveguide.

[0104] In this scheme, the MIM waveguide mode is coupled with the incident light to detect the molecular adsorption process on the outer surface of the sensing structure through surface waves.

[0105] In an operative solution, the defect structure is a non-periodic nanostructure embedded in or penetrating the first metal film layer M1 and inserted into the first periodic structure, or a periodic nanostructure different from the first periodic structure.

[0106] In this scheme, by inserting a defect structure into the first periodic structure, it can be achieved that at a preset optical frequency, in the direction along the plane of the MIM thin film layer, the light waves transmitted along the MIM waveguide dielectric layer are confined near the defect structure, forming a defect-state photonic crystal microcavity of the MIM waveguide, thereby realizing the detection of the molecular adsorption process on the outer surface of the optical structure through surface waves.

[0107] In an implementable solution, the first periodic structure is a structure with a complete periodic arrangement, or a structure after the structure with a complete periodic arrangement is adjusted within a second preset range.

[0108] For example, the second preset range may be to adjust the distance between adjacent units of a completely periodically arranged structure, that is, a structure in which the distances between adjacent units are completely equal, and the adjustment range does not exceed plus or minus 5%, or does not exceed plus or minus 10%.

[0109] In an practicable solution, the thickness of the dielectric layer I is less than a preset thickness;

[0110] The calculation formula of the preset thickness is: preset thickness=(light wavelength in vacuum corresponding to the preset light frequency / refractive index of dielectric layer)×0.5.

[0111] At present, the most efficient preparation process of optical fiber end-face SPR microcavity device is to first prepare the microcavity structure on a wafer substrate, and then peel it off and transfer it to the end face of the optical fiber. The thin dielectric layer I used in this scheme is conducive to this peeling and transfer process.

[0112] Furthermore, while adopting a thinner dielectric layer I, this solution can also achieve a surface wave evanescent depth that is smaller than the evanescent depth of the metal-solution interface SPP in the traditional SPR technology; in addition, by adjusting the material and thickness of the dielectric layer I, the operating wavelength of the device can be flexibly set to meet different requirements for light wavelength, so that the sensor device can adapt to a wider range of detection scenarios.

[0113] In one feasible solution, the nanostructure array is a nanowire groove structure array.

[0114] Specifically, the first nanostructure array A1, the second nanostructure array A2 and the third nanostructure array A3 in the nanostructure arrays are all nanowire groove structure arrays.

[0115] In an operative solution, the second metal film layer M2 does not include a nanostructure array.

[0116] In this solution, no nanostructure array is provided in the second metal film layer M2, which can maintain the smoothness and uniformity of the outer surface of the optical structure, so that the biomolecule adsorption process has higher detection stability and anti-interference ability, ensures the feasibility and accuracy of low-concentration biomolecule detection, and improves the stability and repeatability of biomolecule detection.

[0117] In an operative solution, part or all of the nanostructure array penetrates the first metal film layer M1;

[0118] The penetrating nanostructure is filled with dielectric material, no adhesion layer is provided between the dielectric layer I and the first metal film layer M1, and an adhesion layer is provided between the dielectric layer I and the second metal film layer M2.

[0119] In this solution, dielectric material is filled in the nanostructure that penetrates the first metal film layer M1, and an adhesion layer is provided between the dielectric layer I and the second metal film layer M2, which can stabilize the structure. No adhesion layer is provided between the dielectric layer I and the first metal film layer M1, which can reduce the ohmic loss of the MIM waveguide, thereby significantly optimizing the device performance.

[0120] Specifically, titanium with a thickness of 0.5 to 3 nm can be used as an adhesion layer. In order to fix the first metal film layer M1, the conventional method can be used, that is, an adhesion layer is provided between the dielectric layer I and the first metal film layer M1, or the present solution can be used, that is, a layer of dielectric material is added above the MIM structure and filled into the nanogrooves, so that the dielectric material and the dielectric layer I wrap the first metal film layer M1 in the middle to achieve the purpose of stabilizing the structure; the added dielectric material can be selected from materials such as silicon dioxide or silicon nitride.

[0121] The MIM structure obtained by using different stabilization methods for the first metal film layer M1 and the second metal film layer M2 as described above can effectively reduce the ohmic absorption loss of the MIM waveguide (after hybridization with the SPP) caused by the adhesion layer, thereby obtaining a narrower and deeper SPR resonance valley.

[0122] In an implementable solution, a detection layer for sensing preset environmental parameters is provided on or near the outer side surface of the second metal film layer M2 , and the detection layer is used for sensing and detecting by measuring reflected light of the optical structure.

[0123] In an implementable solution, the detection layer includes, but is not limited to: a detection layer for responding to molecular adsorption, a detection layer for responding to temperature, a detection layer for responding to pressure, and a detection layer for responding to an acoustic field.

[0124] In this solution, a detection layer with other functions (such as detecting electromagnetic fields) can also be provided. To realize the detection function of corresponding parameters, the detection layer only needs to be provided on the sensing surface outside the second metal film layer M2.

[0125] In addition, if Figure 5 As shown, the results of the two-dimensional electromagnetic field simulation of the MIM waveguide photonic crystal microcavity (i.e., the above-mentioned optical structure) at the end face of a single-mode optical fiber in this embodiment are as follows:

[0126] Both the horizontal and vertical axes represent spatial coordinates (in nm), the dotted lines correspond to the boundaries of several structures, and the grayscale represents the square of the electric field amplitude; from top to bottom in the figure: optical fiber (including optical waveguide core Core and optical waveguide cladding Cladding), a first metal film layer M1 made of gold Au material (including a first nanostructure array A1, namely gold grating Au grating), a dielectric layer I made of SiO2, a second metal film layer M2 made of gold Au material (without structure), and a solution layer in contact with the second metal film layer M2, such as water; the optical fiber Core is aligned with the center of the gold grating.

[0127] The optical fiber waveguide (mainly located in the core) is vertically incident and first coupled to the light wave transmitted along the MIM waveguide dielectric layer. Then, based on the hybridization of the MIM waveguide and the surface plasmon polariton SPP, it tunnels and couples to the SPP surface wave of the second metal film layer M2-solution interface in the lower layer. The evanescent depth of this surface wave is only about 175nm, which is more than half smaller than the evanescent depth of the traditional gold-water interface SPP extending to the water side when the underlying gold film is assumed to be infinitely thick.

[0128] The light wavelength corresponding to the above simulation results is 845nm. In this simulation structure, it includes an upper first metal film layer M1 with a thickness of 65nm, made of gold, a SiO2 dielectric material layer with a thickness of 199nm, and a lower second metal film layer M2 with a thickness of 18nm, made of gold; in the upper gold film, there is the following nanowire slot array that runs through the gold film: the width of the central array slot is 81nm, the period is 622nm, and there are 14 periods in total. This part acts as a periodic grating to couple the optical fiber with the MIM waveguide; secondly, the width of the surrounding array slot is 123nm, and the period is 304nm. This part acts as a distributed Bragg reflector to confine the light waves and SPP surface waves transmitted along the MIM waveguide dielectric layer to the microcavity it encloses. The external environment is set to water.

[0129] like Figure 6 As shown, the reflection spectrum simulation results of the above single-mode fiber end face MIM waveguide photonic crystal microcavity device in this embodiment are as follows:

[0130] The horizontal axis represents the wavelength (in nm), and the vertical axis represents the reflectivity. The simulation results are as follows: Figure 6 The light power reflectivity spectrum reflected back to the optical fiber is shown. The resonance valley near 845nm corresponds to the optimal coupling between the optical fiber waveguide and the MIM waveguide photonic crystal microcavity. It is through the wavelength shift of this resonance valley that the binding of biological molecules to the underlying metal surface is detected. By adjusting the material and thickness of the dielectric layer I, the operating wavelength of the device can be flexibly set. The calculation results show that while having a surface sensitivity comparable to that of the fiber end face SPR microcavity in the existing scheme, the optical structure in this scheme is sensitive to the refractive index change of the aqueous solution at about 400nm / RIU, which is significantly lower than the sensitivity of the fiber end face SPR microcavity in the existing scheme to the refractive index change of the aqueous solution, the latter of which is higher than 600nm / RIU (near 850nm light wavelength).

[0131] As proved by the above simulation experiments, the optical structure in this scheme can indeed achieve high sensitivity to changes in the surface refractive index, while reducing sensitivity to changes in the refractive index of the surrounding body, thereby having high sensitivity and stability in detecting the adsorption of biological molecules, and can ensure the feasibility and accuracy of low-concentration biological molecule detection.

[0132] Example 2

[0133] like Figure 7 As shown, the optical waveguide device 100 of this embodiment includes an optical waveguide body 200 and the optical structure 300 in Embodiment 1;

[0134] The incident light illuminates the optical structure 300 via the optical waveguide body 200, and the reflected light returns via the same optical waveguide body 200;

[0135] The side of the optical structure 300 away from the second metal film layer M2 is combined on the end plane of the optical waveguide body 200, and the part of the optical structure 300 constituting the MIM waveguide photonic crystal microcavity is aligned with the waveguide core in the optical waveguide body 200. The optical waveguide body 200 includes but is not limited to an optical fiber.

[0136] In this solution, the optical waveguide device 100 has the advantages of stable transmission, small size, and flexible use. Through the photonic crystal microcavity of the MIM waveguide in the optical structure 300, SPR can be efficiently stimulated, and various optical fiber detection applications can be performed, such as for biological molecule detection, and has a wide range of application scenarios that meet higher detection requirements.

[0137] In an implementable solution, the optical waveguide body 200 is a single-mode optical fiber, and the angle between the MIM film layer in the optical structure 300 and the axis of the single-mode optical fiber is within a preset angle range.

[0138] The preset angle range is any angle range that can meet the detection requirements; preferably, the preset angle range is close to vertical between the two.

[0139] In an implementable solution, the preset angle range is 80° to 90°.

[0140] Specifically, during the device preparation process, the optical structure 300 is first prepared on a quartz glass substrate, and then transferred to the end plane of a single-mode optical fiber, and the portion of the optical structure 300 that constitutes the photonic crystal microcavity of the MIM waveguide is aligned with the waveguide core of the optical fiber.

[0141] like Figure 8 , which is a schematic structural diagram of the optical waveguide device 100 , in which the optical structure 300 is fixedly arranged on the end plane of the optical waveguide body 200 .

[0142] in, Figure 8L1 corresponds to the adhesion layer, P corresponds to the protective layer arranged above the first metal film layer M1, the protective layer P adopts dielectric material, and the dielectric material is filled into the penetrating nanostructure in the first metal film layer M1, so that the protective layer P and the dielectric layer I together wrap and stabilize the first metal film layer M1, L2 is the connecting layer that fixes the protective layer P to the end face of the optical waveguide body 200, Core is the optical waveguide core, and Cladding is the optical waveguide cladding.

[0143] like Fig. 9 The figure shows a local SEM image of a MIM waveguide photonic crystal microcavity (Plasmonic Crystal Microcavity) taken before the optical structure is transferred to the fiber end face. A two-dimensional periodic nanowire slot array arranged in a square pattern is used here. The other parameters are the same as those used in the above two-dimensional simulation, and also include a central array ( Fig. 9 B1 region in the ) and a surrounding array ( Fig. 9 B2 area in the figure).

[0144] In biomolecular sensing experiments, such as Fig.10 As shown, the whole experimental device includes a superluminescent diode (SULD), a spectrometer, and a directional coupler. The superluminescent diode and the spectrometer are connected to the directional coupler through a single-mode optical fiber. The directional coupler is connected to the MIM waveguide photonic crystal microcavity sensor (i.e., the above-mentioned optical structure 300) at the end face of the optical fiber through the single-mode optical fiber. The sensor is inserted into the sample solution to be tested for detection. Among them, the broadband light emitted by the superluminescent diode is coupled to the single-mode optical fiber, and the light is guided to the MIM waveguide photonic crystal microcavity at the end face of the optical fiber through the optical fiber directional coupler. The reflected light is then guided to the optical fiber spectrometer to measure the reflection spectrum through the directional coupler. The optical structure 300 is inserted into the sample to be tested, and the monitoring of the molecule binding to the sensing interface is realized by reading the resonance valley wavelength of the reflection spectrum.

[0145] First, the interaction between streptavidin (SA) and biotinylated molecules was measured. HS-PEG-biotin-streptavidin (HS-PEG-biotin-SA) and HS-PEG were first fixed on the outer surface of the second metal film layer M2 of the MIM waveguide photonic crystal microcavity sensor. Then the sensor was immersed in a biotinylated bovine serum albumin (bio-BSA) solution. The concentration of bio-BSA molecules ranged from 30fM to 1μM.

[0146] like Fig.11As shown, the horizontal axis represents time (unit: s), the vertical axis represents the movement of the resonance valley wavelength Wavelength of the reflection spectrum (unit: nm), and PBS represents phosphate buffered saline solution without bio-BSA molecules; the figure shows the real-time sensing curve of the sensor immersed in bio-BSA molecular solutions of different concentrations, where the wavelength movement corresponds to the number of bio-BSA molecules captured on the sensor surface, and the detectable concentration of bio-BSA can be as low as 30fM; such high sensitivity is directly related to the very stable baseline and small temperature drift of the sensor, and these excellent characteristics are directly derived from the smooth sensing surface and the shorter surface wave evanescent depth.

[0147] In addition, in order to verify that a smooth sensing surface can bring highly stable and highly repeatable sensor performance, protein A molecules (proteinA) were fixed on the outer surface of the second metal film layer M2 of the MIM waveguide photonic crystal microcavity sensor. The sensor was then used to bind to human immunoglobulin G molecules (hIgG) in the solution, and then to bind to antibodies against hIgG (anti-hIgG). Finally, the hIgG and anti-hIgG bound to the sensor were removed (regeneration) using a regeneration solution, and the above process was repeated in a cycle.

[0148] like Fig.12 As shown, the horizontal axis represents time (unit: s), and the vertical axis represents the movement of the resonance valley wavelength Wavelength of the reflection spectrum (unit: nm). Specifically, the concentrations of the hIgG molecule solution and the anti-hIgG molecule solution are both 100 μg / mL. The figure shows the real-time sensing curves of 4 cycle experiments.

[0149] like Fig.13 As shown, the horizontal axis represents time (unit: s), and the vertical axis represents the movement amount of the resonance valley wavelength Wavelength of the reflection spectrum (unit: nm). Fig.13 By superimposing the four cycle experimental curves in , it can be seen that the four cycle experimental curves are basically overlapping, thus demonstrating the good stability and repeatability of the sensor device, which is difficult to achieve for the SPR sensor with an uneven nanostructure on the surface.

[0150] Although the specific embodiments of the present disclosure are described above, those skilled in the art should understand that this is only an example, and the protection scope of the present disclosure is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present disclosure, but these changes and modifications all fall within the protection scope of the present disclosure.

Claims

1. An optical structure, characterized in that: The optical structure comprises a first metal film layer, a dielectric layer and a second metal film layer sequentially arranged along a light incident direction, wherein the first metal film layer, the dielectric layer and the second metal film layer form a MIM film layer; The first metal film layer is provided with a first nanostructure array, and the outer side surface of the second metal film layer is smooth and uniform; The first nanostructure array is embedded in or penetrates the first metal film layer; The duty cycle of the first nanostructure array is greater than 50%; The duty cycle is a first ratio of a length of a non-affected region in the first nanostructure array in one dimension to a total length of the first nanostructure, or a second ratio of an area of ​​the non-affected region in the first nanostructure in two dimensions to a total area of ​​the first nanostructure array; The optical structure is used to couple incident light of a preset optical frequency to a surface wave propagating along the outer side surface of the second metal film layer.

2. The optical structure according to claim 1, characterized in that: The optical structure is used to couple the incident light of the preset optical frequency to the light wave propagating along the MIM waveguide dielectric layer and the surface wave propagating along the outer side of the second metal film layer; Wherein, the MIM waveguide is formed in the MIM thin film layer.

3. The optical structure according to claim 1, characterized in that: The first evanescent depth of the surface wave is less than a preset evanescent depth corresponding to a preset surface plasmon polariton SPP; The preset evanescent depth is the evanescent depth of the surface plasmon polaritons SPP along the outer side surface of the second metal film layer at the preset light frequency when assuming that the second metal film layer is infinitely thick.

4. The optical structure according to claim 1, characterized in that The first nanostructure array includes a first periodic structure with a first preset period, wherein the first preset period is smaller than a preset wavelength corresponding to a surface plasmon polariton SPP; The preset wavelength is the wavelength of the surface plasmon polaritons SPP along the outer side of the second metal film layer at the preset light frequency when the second metal film layer is assumed to be infinitely thick; The optical structure is used to couple the incident light of the preset optical frequency whose transmission direction is perpendicular to the MIM film layer or whose angle with the direction perpendicular to the MIM film layer is less than a set value to the surface wave propagating along the outer side of the second metal film layer.

5. The optical structure according to claim 4, characterized in that: The nanostructure array further includes a second nanostructure array, wherein the second nanostructure array includes a second periodic structure with a second preset period; Wherein, a MIM waveguide is formed in the MIM thin film layer; The second periodic structure surrounds the first periodic structure in a direction along the plane of the MIM film layer and is located at a first preset position in a direction perpendicular to the plane of the MIM film layer; Under the preset optical frequency, the second periodic structure reflects the light waves transmitted along the MIM waveguide dielectric layer, and confines the light waves transmitted along the MIM waveguide dielectric layer in the direction along the plane of the MIM thin film layer within and near the space surrounded by the second periodic structure, thereby forming a photonic crystal microcavity of the MIM waveguide.

6. The optical structure according to claim 5, characterized in that: The second periodic structure is embedded in or penetrates the first metal film layer, and the second preset period is smaller than the first preset period.

7. The optical structure according to claim 5, characterized in that: The first periodic structure and / or the second periodic structure is a structure with a complete periodic arrangement, or a structure after the complete periodic arrangement is adjusted within a first preset range.

8. The optical structure according to claim 4, characterized in that: The nanostructure array further includes a third nanostructure array, wherein the third nanostructure array includes a single or multiple defect structures; Wherein, a MIM waveguide is formed in the MIM thin film layer; The defect structure is inserted into the first periodic structure in a direction along the plane of the MIM film layer, and is located at a second preset position in a direction perpendicular to the plane of the MIM film layer; At the preset optical frequency, in the direction along the plane of the MIM thin film layer, the light wave transmitted along the MIM waveguide dielectric layer is confined near the defect structure, forming a defect state photonic crystal microcavity of the MIM waveguide.

9. The optical structure according to claim 8, characterized in that: The defect structure is a non-periodic nanostructure embedded in or penetrating the first metal film layer and inserted into the first periodic structure, or a periodic nanostructure different from the first periodic structure.

10. The optical structure according to claim 8, characterized in that: The first periodic structure is a structure with a complete periodic arrangement, or a structure after the structure with a complete periodic arrangement is adjusted within a second preset range.

11. The optical structure according to any one of claims 1 to 10, characterized in that: The thickness of the dielectric layer is less than a preset thickness; The calculation formula of the preset thickness is: the preset thickness=(the wavelength of light in vacuum corresponding to the preset light frequency / the refractive index of the dielectric layer)×0.

5.

12. The optical structure according to any one of claims 1 to 10, characterized in that: The nanostructure array is a nanowire groove structure array.

13. The optical structure according to any one of claims 1 to 10, characterized in that: The second metal film layer does not include a nanostructure array.

14. The optical structure according to any one of claims 1 to 10, characterized in that: Part or all of the nanostructure array penetrates the first metal film layer; The penetrating nanostructure is filled with a dielectric material, no adhesion layer is provided between the dielectric layer and the first metal film layer, and an adhesion layer is provided between the dielectric layer and the second metal film layer.

15. The optical structure according to any one of claims 1 to 10, characterized in that: The duty cycle of the first nanostructure array is greater than 70%.

16. The optical structure according to any one of claims 1 to 10, characterized in that: A detection layer for sensing preset environmental parameters is provided on the outer side surface or near the outer side surface of the second metal film layer, and the detection layer is used for sensing and detecting by measuring the reflected light of the optical structure.

17. The optical structure according to claim 16, characterized in that: The detection layer includes at least one of the following: A detection layer for responding to molecular adsorption, a detection layer for responding to temperature, a detection layer for responding to pressure, and a detection layer for responding to an acoustic field.

18. An optical waveguide device, characterized in that: The optical waveguide device comprises an optical waveguide body, and an optical structure as claimed in any one of claims 1 to 17; The incident light irradiates the optical structure via the optical waveguide body, and the reflected light returns via the same optical waveguide body; The side of the optical structure away from the second metal film layer is bonded to the end plane of the optical waveguide body, and the part of the optical structure constituting the MIM waveguide photonic crystal microcavity is aligned with the waveguide core in the optical waveguide body.

19. The optical waveguide device according to claim 18, wherein: The optical waveguide body is a single-mode optical fiber, and the angle between the MIM film layer in the optical structure and the axis of the single-mode optical fiber is within a preset angle range.

20. The optical waveguide device according to claim 19, wherein: The preset angle range is 80° to 90°.

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