A wavelength-controlled graphene metasurface photonic crystal surface wave optical device

Abstract

The present invention discloses a graphene metasurface photonic crystal surface wave optical device that realizes wavelength control, and its cross section includes a cladding layer, a graphene metasurface, and a multilayer film structure element. By adjusting the refractive index or thickness of the cladding layer or a layer structure therein, input light is incident on the surface of the optical device at a specific angle, and the significantly enhanced light field is confined to the graphene metasurface, thereby enhancing the interaction between graphene and light. The metasurface micro-nanostructure is used to control the transmission and spatial distribution of the photonic crystal surface wave light field, modulate the amplitude, phase, and frequency response, and realize frequency selection and wavelength control effects, thereby obtaining a photonic crystal surface wave effect with significantly improved sensing sensitivity. The proposed optical device is of great significance for realizing photonic crystal surface waves in its potential application fields, mainly including optical switches, optical storage and other optoelectronic devices in optical communications, and optical sensing detection in the sensing field.

Description

Technical Field

[0001] The present invention relates to the field of optical surface waves, and in particular to a graphene supersurface photonic crystal surface wave optical device capable of achieving wavelength control. Background Art

[0002] Photonic crystal surface wave sensing is a highly sensitive optical sensing method based on the interaction of light waves between dielectric surfaces. Because it obtains sensing information based on changes in refractive index, it offers a novel label-free approach for dynamical research. In the 1970s, Yeh et al. theoretically demonstrated that a truncated photonic crystal plane can support the transmission of surface electromagnetic waves. Based on Bloch theory, a photonic band gap (PBG), also known as a band gap, exists in photonic crystals composed of periodic alternating dielectric layers. Due to the presence of a PBG, the wave vector of a light wave has no real part within this frequency band gap, meaning that the light wave cannot propagate as a wave, but rather as an evanescent wave with exponentially decaying electromagnetic fields. To excite this mode, a layer of dielectric material can be introduced at the end of the photonic crystal structure to induce surface waves on the surface. These surface waves, which exist at the end of the PBG structure and propagate along the interface, are called photonic crystal surface waves. Their profound physical implications and potential applications have sparked widespread research interest. Twenty years later, Roberson et al. successfully excited photonic crystal surface waves in an experiment. Since then, numerous scholars both domestically and internationally have developed a keen interest in photonic crystal surface waves, and research publications on this technology have increased exponentially. Photonic crystal surface waves have important applications in studying the physical mechanisms of light-matter interactions at interfaces or surfaces, as well as in the development of related optical technologies. They provide a crucial research tool for fields including sensing and integrated photonic devices.

[0003] Photonic crystal surface waves (PCS) share many similarities with surface plasmon waves (SPWs) that exist on the surfaces of metals and dielectrics. Both are confined at the interface between two materials, causing field enhancement at the interface and penetrating into each material exponentially. With the deepening of research into surface plasmon resonance (SPR) technology based on SPRs, the study of PCS waves has attracted increasing attention in recent years. Compared to SPRs, which can only be excited by p-polarization, PCS waves can be excited at any wavelength and with any polarization state by appropriately designing the photonic crystal's materials and structure. Furthermore, because the structure lacks metal, the losses of PCS waves are much lower than those of SPWs. Furthermore, because the field confinement of dielectric structures is less robust than that of metals, the penetration depth of PCS waves can be greater than that of SPWs. By comparison, we can see that the excitation of photonic crystal surface waves depends on the design of the photonic crystal structure, with almost no restrictions on wavelength and polarization, and its loss is much smaller than that of surface plasmon waves, and its penetration depth is much greater. By modifying the surface with a three-dimensional long-chain structure, it is possible to provide more molecular binding sites and achieve a larger amount of molecular adsorption. Therefore, it is expected to achieve a design with better performance in aspects such as biochemical molecular detection and photonic device design.

[0004] Previous research on photonic crystal surface wave sensing has mostly focused on measuring the reflected light intensity and the shift of the coupled absorption peak on a truncated one-dimensional photonic crystal surface. The structure proposed in this paper controls the transmission and spatial distribution of the light field by introducing a specific metasurface micro-nanostructure onto the device surface. This modulates the amplitude, phase, and frequency of the light field localized on the device surface, thereby realizing a wavelength-controllable photonic crystal surface wave optical system. Summary of the Invention

[0005] Therefore, the task of the present invention is to provide a wavelength-controllable graphene metasurface photonic crystal surface wave optical device to address the problem that it is difficult to achieve spatial light field control in the existing photonic crystal surface wave device structure.

[0006] The present invention provides a wavelength-adjustable graphene supersurface photonic crystal surface wave optical device, which comprises a cladding layer, a graphene supersurface and a multilayer film structural element.

[0007] The graphene supersurface may cover the surface of the coating layer, or may be partially or completely embedded in the coating layer.

[0008] The multi-layer film structural element may cover the surface of the coating layer, or may be partially or completely embedded in the coating layer.

[0009] The graphene super surface in the device is composed of a graphene micro-nano structure array.

[0010] The function of the graphene layer and the multilayer film structure element in the device is to excite photonic crystal surface waves on the graphene surface by adjusting the physical properties of the cladding layer or a layer structure therein.

[0011] The device functions by exciting photonic crystal surface waves by incident light at a specific angle on a graphene metasurface. The graphene metasurface then produces different amplitude, phase, and frequency responses to the polarization components of the incident light beam, causing the spatial light field distribution corresponding to the polarization components in the reflected light beam passing through the device to vary over a portion of the spatial region relative to the spatial light field distribution of the incident light beam, thereby achieving a wavelength-tunable photonic crystal surface wave effect. For the operating wavelength of the incident light beam, the photonic crystal surface wave optical device exhibits a phase variation within the angular interval [α, β]. The angular interval refers to the angular range within which the structure exhibits a phase variation at the interface between the cladding layer adjacent to the graphene layer and the graphene metasurface, with α being the lower limit and β being the upper limit. The critical value for total internal reflection at the interface between the cladding layer adjacent to the graphene layer and the graphene metasurface is γ, where γ < β.

[0012] The device can control the refractive index of the cladding layer by changing the cladding layer material; it can also utilize thermo-optical effect, magneto-optical effect, acousto-optic effect, electro-optical effect, optical Kerr effect or elastic-optical effect, etc., by changing the temperature, magnetic field, acoustic wave field, electric field, light intensity or stress, etc., to control the refractive index or thickness of each layer in the cladding layer, graphene metasurface and multilayer film structure element, thereby achieving a wavelength control effect.

[0013] In one embodiment, the multilayer film structure element in the device can be formed by alternating two or more all-dielectric material layers with different refractive indices; or it can be composed of one or more transparent dielectrics, metals, absorbing materials, left-handed artificial materials, etc.

[0014] In a more preferred embodiment, the multilayer film structure element includes a transparent dielectric substrate and a multilayer dielectric material layer in sequence, wherein the multilayer dielectric material layer is formed by alternating two or more dielectric material layers with different refractive indices.

[0015] In one example, the refractive index of the high-refractive-index medium layer is higher than the refractive index of the low-refractive-index medium and the cladding layer.

[0016] In one example, the materials of the low-refractive-index medium and the cladding layer can be the same material or different materials.

[0017] In one example, a ratio of a maximum refractive index of the low-refractive-index medium and the cladding layer to a refractive index of the high-refractive-index medium layer is less than 0.75.

[0018] In one embodiment, the high refractive index dielectric material layer in the device can be made of any one of titanium dioxide, silicon nitride, zinc sulfide, cerium oxide, and zirconium oxide.

[0019] In one embodiment, the low refractive index dielectric material in the device can be any one of silicon dioxide, magnesium difluoride, and cryolite.

[0020] Preferably, the multilayer dielectric material layers having different refractive indices in the multilayer film structure element may be alternately stacked with high-refractive-index dielectric material layers and low-refractive-index dielectric material layers. The high and low refractive indices of the high and low-refractive-index dielectric material layers are relative; that is, the refractive index of the high-refractive-index dielectric material layer is higher than that of the low-refractive-index dielectric material layer.

[0021] In a more preferred embodiment, the high refractive index dielectric material of the multilayer dielectric material layer in the multilayer film structure element is titanium dioxide; the low refractive index dielectric material of the multilayer dielectric material layer in the multilayer film structure element is silicon dioxide.

[0022] The thickness of each layer in the multilayer film structure element in the device is selected so that a photonic band gap can be generated in the multilayer film structure element at a certain working wavelength, thereby exciting a photonic crystal surface wave.

[0023] In one embodiment, the thickness d of the i-th layer in the multilayer film structural element is i Determined by the following formula:

[0024]

[0025] Where λ is the wavelength of the transmitted optical signal, n i ,θ i are the refractive index of the medium in the i-th layer and the incident angle of the light wave in the i-th layer, respectively. Wherein, i is a natural number between 1 and the maximum number of layers in the multilayer film structure.

[0026] The graphene supersurface in the device is connected to a multilayer dielectric material layer, which can be used to adjust the excitation position of the photonic crystal surface wave in the photonic band gap, thereby achieving wavelength regulation.

[0027] In one example, the thickness of the graphene supersurface micro-nanostructure of the photonic crystal surface wave optical device can be changed to change the reflection resonance peak of the output light beam, thereby achieving wavelength control.

[0028] In one embodiment, the graphene supersurface is a single layer or multilayer graphene with a thickness of 0.34 nm to 3.4 nm.

[0029] In one example, the thickness of the graphene supersurface is preferably 0.34 nm-3.4 nm, more preferably 1.02 nm-2.72 nm, and more preferably 1.5-2.52 nm.

[0030] In one example, using the above-mentioned wavelength control system, the filling factor of the graphene metasurface micro-nanostructure in the photonic crystal surface wave optical device can be changed to change the reflection resonance peak of the output light beam, thereby achieving wavelength control.

[0031] In one embodiment, the filling factor of the graphene supersurface micro-nanostructure array is 0-1.

[0032] In one embodiment, the filling factor of the graphene supersurface micro-nanostructure array is preferably 0.1-0.9, more preferably 0.2-0.8, and more preferably 0.6.

[0033] In one embodiment, the wavelength-controlled photonic crystal surface wave effect is manifested as a position shift of the reflection resonance peak.

[0034] In one example, by changing the physical properties (such as refractive index, etc.) of the external medium adjacent to the surface of the photonic crystal surface wave device, the corresponding photonic crystal surface wave reflection effect can be changed.

[0035] In one example, the physical properties (such as refractive index, etc.) of the external medium adjacent to the surface of the polarization-related wavelength control device can be obtained by detecting changes in the reflection effect of the output light beam, thereby achieving high-sensitivity sensing detection.

[0036] The graphene metasurface photonic crystal surface wave optical device for achieving wavelength control of the present invention has the following advantages:

[0037] 1. The present invention designs a graphene metasurface photonic crystal surface wave optical device that realizes wavelength control. It adopts a multilayer film structure element loaded by a graphene metasurface, and uses the metasurface micro-nano structure to control the transmission and spatial distribution of the photonic crystal surface wave light field. By modulating the amplitude, phase and frequency response through the local field enhancement effect generated when the photonic crystal surface wave is excited on the graphene metasurface, the frequency selection and wavelength control effects are realized.

[0038] 2. The graphene metasurface photonic crystal surface wave optical device designed by the present invention to achieve wavelength control can effectively realize the application of graphene in the field of new optical and optoelectronic devices by confining the significantly enhanced light field to the graphene metasurface and enhancing the interaction between graphene and light. Through the metasurface frequency selection and wavelength control effects,

[0039] 3. The wavelength-controlled graphene metasurface photonic crystal surface wave optical device proposed in the present invention is used for surface wave-based sensing detection to achieve high-sensitivity sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of the structure of a wavelength-controlled graphene metasurface photonic crystal surface wave optical device.

[0041] Figure 2 This is a schematic diagram of the structure of the wavelength-controlled graphene metasurface photonic crystal surface wave optical device described in Example 1.

[0042] Figure 3 This is a partially enlarged view of the wavelength-controlled graphene metasurface photonic crystal surface wave optical device structure described in Example 1.

[0043] Figure 4 The graphene metasurface photonic crystal surface wave optical device with wavelength control described in Example 1 shows a curve showing a change in reflection resonance peak intensity when the filling factor of the graphene metasurface micro-nanostructure array is changed and the external medium is water.

[0044] Figure 5 The reflection phase change curve of the wavelength-controlled graphene metasurface photonic crystal surface wave optical device described in Example 1 is when the filling factor of the graphene metasurface micro-nanostructure array is changed.

[0045] Figure 6 This is the wavelength intensity reflection spectrum sensing curve obtained by the wavelength-controlled graphene metasurface photonic crystal surface wave optical device described in Example 1 as the refractive index of the external medium changes.

[0046] Figure 7 This is a schematic diagram of the structure of the wavelength-controlled graphene metasurface photonic crystal surface wave optical device described in Example 2.

[0047] Figure 8 This is a partially enlarged view of the wavelength-controlled graphene metasurface photonic crystal surface wave optical device structure described in Example 2.

[0048] Figure 9 The graphene supersurface photonic crystal surface wave optical device with wavelength control described in Example 2 shows a curve showing a change in the reflection resonance peak intensity when the thickness of the graphene supersurface micro-nanostructure array is changed.

[0049] Figure 10 The reflection phase change curve of the wavelength-controlled graphene metasurface photonic crystal surface wave optical device described in Example 2 is when the thickness of the graphene metasurface micro-nanostructure array is changed. DETAILED DESCRIPTION

[0050] Example 1: Graphene metasurface photonic crystal surface wave optical device structure with adjustable filling factor

[0051] Figure 2 This is a schematic diagram of the structure of the wavelength-controlled graphene metasurface photonic crystal surface wave optical device described in Example 1. Figure 3 This is a partial enlarged view of the wavelength-controlled graphene metasurface photonic crystal surface wave optical device structure described in Example 1. 201 is the cladding layer, n c is its refractive index; 202 is the graphene supersurface micro-nanostructure array with an array period of 500nm, w g is the width of the micro-nanostructure, n g is its refractive index, FF is its filling factor, which is defined as the ratio of the width of the micro-nanostructure to the array period, that is: FF = w g / 500; 203 is a multilayer dielectric material layer of a multilayer film structure element; 204 is a low refractive index dielectric layer of a multilayer dielectric material layer of a multilayer film structure element, n l Its refractive index, d l 205 is a high refractive index dielectric layer of a multilayer dielectric material layer of a multilayer film structure element, n h Its refractive index, d h is its height (a plurality of low-refractive-index medium layers 204 and high-refractive-index medium layers 205 are superimposed on each other to form a multilayer dielectric material layer 203); 206 is a transparent dielectric substrate of the multilayer film structure element.

[0052] In this example, the material of the cladding layer 201 is set to water, whose refractive index is 1.33; the role of the graphene metasurface 202 is to excite the photonic crystal surface wave, and then the graphene metasurface produces different amplitude, phase and frequency responses to the polarization component in the incident light beam, so that the spatial light field distribution corresponding to the polarization component in the reflected light beam passing through the device changes relative to the spatial light field distribution of the incident light beam in a partial spatial area, so as to obtain a wavelength-controllable photonic crystal surface wave effect.

[0053] In the visible light range, the refractive index expression of graphene is:

[0054] n g =3+i5.446λ / 3

[0055] Where λ is the wavelength in μm.

[0056] The material of the low refractive index dielectric layer 204 in the multilayer film structure element 203 is set to silicon dioxide, whose refractive index is 1.443; the number of periods of the multilayer dielectric material layer in the multilayer film structure element 203 is 7; the material of the high refractive index dielectric layer 205 in the multilayer film structure element 203 is set to titanium dioxide, whose refractive index is 2.314; the material of the transparent dielectric substrate 206 in the multilayer film structure element 203 is ZF10 glass, whose refractive index is 1.6748 (at a wavelength of 785nm).

[0057] In this example, the thickness of the graphene metasurface 202 is 1 nm, the filling factor FF is in the range of 0.1-1, and the height d of the low refractive index medium layer 204 is l =300nm; height d of the high refractive index medium layer 205 h =130nm.

[0058] The full vector finite element method is used to simulate the above-mentioned device structure in this embodiment, and the wavelength control characteristics of the proposed graphene metasurface photonic crystal surface wave optical device structure are calculated.

[0059] Figure 4 The graphene supersurface photonic crystal surface wave optical device with wavelength controllable is characterized by a change in the reflection resonance peak intensity when the filling factor of the graphene supersurface micro-nanostructure array is changed and the external medium is water. Figure 4 It can be seen that with the increase of the filling factor, the excitation wavelength of the photonic crystal surface wave resonance absorption peak gradually moves to a longer wavelength, realizing the wavelength-controllable photonic crystal surface wave effect.

[0060] Figure 5 The curve of the reflection phase change of the wavelength-controlled graphene supersurface photonic crystal surface wave optical device is shown in the example when the filling factor of the graphene supersurface micro-nanostructure array is changed. Figure 5 It can be seen that with the increase of filling factor, the excitation of photonic crystal surface waves is accompanied by a dramatic phase jump and gradually moves to a longer wavelength, realizing the wavelength-controllable photonic crystal surface wave effect.

[0061] Figure 6 The wavelength intensity reflection spectrum sensing curve obtained by the wavelength-controlled graphene metasurface photonic crystal surface wave optical device as the refractive index of the external medium changes. The filling factor FF is 0.6. Figure 6 It can be seen that as the refractive index of the sample changes, the wavelength of the reflection resonance peak shifts significantly, achieving high-sensitivity wavelength sensing detection.

[0062] Example 2: Thickness-adjustable graphene metasurface photonic crystal surface wave optical device structure

[0063] Figure 7This is a schematic diagram of the structure of the wavelength-controlled graphene metasurface photonic crystal surface wave optical device described in Example 2. Figure 8 This is a partial enlarged view of the wavelength-controlled graphene metasurface photonic crystal surface wave optical device structure described in Example 2. 801 is the cladding layer, n c is its refractive index; 802 is the graphene supersurface micro-nanostructure array, n g Its refractive index, d g 803 is a multilayer dielectric material layer of a multilayer film structure element; 804 is a low refractive index dielectric layer of a multilayer dielectric material layer of a multilayer film structure element, n l Its refractive index, d l 805 is the high refractive index dielectric layer of the multilayer dielectric material layer of the multilayer film structure element, n h Its refractive index, d h is its height (multiple low-refractive-index medium layers 804 and high-refractive-index medium layers 805 are superimposed on each other to form a multilayer dielectric material layer 803); 806 is the transparent dielectric substrate of the multilayer film structure element.

[0064] In this example, the material of the cladding layer 801 is set to water, whose refractive index is 1.33; the function of the graphene metasurface 802 is to excite the photonic crystal surface wave, and then the graphene metasurface produces different amplitude, phase and frequency responses to the polarization component in the incident light beam, so that the spatial light field distribution corresponding to the polarization component in the reflected light beam passing through the device changes relative to the spatial light field distribution of the incident light beam in a partial spatial area, so as to obtain a wavelength-controllable photonic crystal surface wave effect.

[0065] In the visible light range, the refractive index expression of graphene is:

[0066] n g =3+i5.446λ / 3

[0067] Where λ is the wavelength in μm.

[0068] The material of the low refractive index dielectric layer 804 in the multilayer film structure element 803 is set to silicon dioxide, whose refractive index is 1.443; the number of periods of the multilayer dielectric material layer in the multilayer film structure element 803 is 7; the material of the high refractive index dielectric layer 805 in the multilayer film structure element 803 is set to titanium dioxide, whose refractive index is 2.314; the material of the transparent dielectric substrate 806 in the multilayer film structure element 803 is ZF10 glass, whose refractive index is 1.6748 (at a wavelength of 785nm).

[0069] In this example, the thickness of the graphene metasurface 802 ranges from d g =1nm-3nm, the filling factor FF is 0.6, and the height d of the low refractive index medium layer 804 isl =300nm; height d of the high refractive index medium layer 805 h =130nm.

[0070] The full vector finite element method is used to simulate the above-mentioned device structure in this embodiment, and the wavelength control characteristics of the proposed graphene metasurface photonic crystal surface wave optical device structure are calculated.

[0071] Figure 9 The graphene supersurface photonic crystal surface wave optical device with wavelength controllable is characterized by a change in the reflection resonance peak intensity when the thickness of the graphene supersurface micro-nanostructure array is changed and the external medium is water. Figure 9 It can be seen that with the increase of thickness, the excitation wavelength of the photonic crystal surface wave resonance absorption peak gradually moves to a longer wavelength, realizing the wavelength-controllable photonic crystal surface wave effect.

[0072] Figure 10 The graphene supersurface photonic crystal surface wave optical device reflection phase change curve of the wavelength controlled graphene supersurface when the thickness of the graphene supersurface micro-nanostructure array is changed. Figure 10 It can be seen that as the thickness increases, the excitation of the photonic crystal surface wave is accompanied by a dramatic phase jump and gradually moves to a longer wavelength, realizing the wavelength-controllable photonic crystal surface wave effect.

[0073] In summary, the present invention integrates a graphene metasurface micro-nanostructure array on the surface of a multilayer film structure element. By confining the significantly enhanced light field to the graphene metasurface, the interaction between graphene and light is enhanced, and photonic crystal surface waves (PCSWs) are excited on the graphene metasurface. Through the metasurface's frequency selection and wavelength control effects, a wavelength-controlled graphene metasurface PCSW optical device is realized. This can effectively enhance the sensing sensitivity of PCSWs and enable the application of PCSWs in novel optical and optoelectronic devices.

[0074] Finally, it should be noted that the above embodiments are intended only to illustrate the structure, technology, and application of the wavelength-controlled graphene metasurface photonic crystal surface wave optical device of the present invention, but are not intended to be limiting. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art will understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention and are intended to be encompassed by the claims of the present invention.

Claims

1. A wavelength-controlled graphene metasurface photonic crystal surface wave optical device, characterized in that: It includes a cladding layer, a multilayer film structure element and a graphene supersurface sandwiched between the cladding layer and the multilayer film structure element; the multilayer film structure element includes a transparent dielectric substrate and a multilayer dielectric material layer, wherein the multilayer dielectric material layer is formed by alternating high-refractive index dielectric material layers and low-refractive index dielectric material layers; the graphene supersurface is connected to the multilayer dielectric material layer, and is composed of a single-layer or multi-layer graphene micro-nanostructure array with a thickness of 0.34nm-3.4nm and a filling factor of 0-1.

2. The optical device according to claim 1, wherein The refractive index of the material of the high refractive index dielectric layer in the device is higher than the refractive index of the material of the low refractive index dielectric layer and the cladding layer. The materials of the low refractive index dielectric layer and the cladding layer are the same material or different materials. The ratio of the maximum refractive index of the material of the low refractive index dielectric layer and the cladding layer to the refractive index of the material of the high refractive index dielectric layer is less than 0.

75.

3. The optical device according to claim 1, wherein For the working wavelength of the incident light beam, the photonic crystal surface wave optical device has a phase change in the angle range [α, β]. The critical angle for total internal reflection of the device at the interface between the cladding layer adjacent to the graphene layer and the graphene metasurface is γ, and γ<β.

4. The optical device according to claim 1, wherein The device can control the refractive index of the cladding layer by changing the cladding layer material; it can also use the thermo-optical effect, magneto-optical effect, acousto-optic effect, electro-optical effect, optical Kerr effect or elastic-optic effect to control the refractive index or thickness of the cladding layer, graphene metasurface and each layer in the multilayer film structure element by changing the temperature, magnetic field, acoustic wave field, electric field, light intensity or stress, thereby achieving a wavelength control effect.

5. The optical device according to claim 1, wherein The high refractive index dielectric material in the device can be any one of titanium dioxide, silicon nitride, zinc sulfide, cerium oxide, and zirconium oxide; the low refractive index dielectric material in the device can be any one of silicon dioxide, magnesium difluoride, and cryolite.

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