A silicon dioxide-based hyperbolic metasurface and a preparation method and application thereof

Abstract

The present application belongs to the technical field of metasurface and micro-nano photonics, and particularly relates to a hyperbolic metasurface based on silicon dioxide and a preparation method and application thereof. The hyperbolic metasurface based on silicon dioxide provided by the present application has a nano-grating structure composed of several strip-shaped silicon dioxide, can generate hyperbolic phonon polariton in the 8-10 mu m wave band, is conducive to converging light energy to a specific area, realizes effective compression of light, and moreover, the wave band is located in the atmospheric window, can be used for long-distance infrared thermal imaging, is helpful to improving the performance of photoelectric detectors and mid-infrared wave band metasurface imaging, and moreover, the metasurface has high integration, and thus is convenient for photon integration. The hyperbolic metasurface of the present application can be applied to metasurface imaging and light energy transmission devices, is made into a super lens, realizes focusing light in a place smaller than a wavelength, the tighter the focused light, the smaller the focal point, and the higher the resolution of the image, and is suitable for super-high-density integrated optical path design.

Description

Technical Field

[0001] This invention belongs to the field of metasurface and micro / nano photonics technology, specifically relating to a hyperbolic metasurface based on silicon dioxide, its preparation method, and its applications. Background Technology

[0002] Polaritons, capable of breaking the traditional optical diffraction limit and compressing and manipulating light wavelengths at the nanoscale, have become a hot topic in nanophotonics research in recent years. Phonon polaritons are quasiparticles generated by the coupling of photons with optical phonons produced by lattice vibrations in polar crystals. Due to the lower optical loss in polar materials, the quality factor of phonon polaritons is generally superior to that of plasmonic polaritons, and they can produce a strong field enhancement effect within specific wavelength bands.

[0003] Hyperbolic metasurfaces possess two effective relative permittivityes in the plane: εeff,x and εeff,y, with opposite signs. In this material, phonon polaritons exhibit hyperbolic plane dispersion, propagating anisotropically in a plane. By constructing hyperbolic metasurfaces, in-plane phonon coupling can be achieved, forming in-plane hyperbolic wavefronts. This has significant implications for the compression and manipulation of optical wavelengths.

[0004] The mid-infrared band (2.5–25 μm) includes two atmospheric windows (3–5 μm and 8–14 μm), which can be used to detect the infrared light emitted by a target object for long-range infrared thermal imaging. However, each material generates surface plasmons or phonon polaritons only in specific bands. For the 8–10 μm band, there are currently few applications of phonon polaritons in this band. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a hyperbolic metasurface based on silicon dioxide, its preparation method and application. The hyperbolic metasurface based on silicon dioxide provided by the present invention can generate hyperbolic phonon polaritons in the 8-10 μm band, achieving effective light compression, which helps to improve the performance of mid-infrared photodetectors and mid-infrared metasurface imaging.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The present invention provides a hyperbolic metasurface based on silicon dioxide, comprising a substrate 1 and a silicon dioxide metasurface 2 located on the substrate 1, characterized in that the silicon dioxide metasurface 2 has a nanograting structure; the nanograting structure is composed of a plurality of strips of silicon dioxide.

[0008] Preferably, the strip-shaped silicon dioxide has a length of 5–20 μm and a width of 50–200 nm.

[0009] Preferably, the gap between the strip-shaped silicon dioxide is 10–200 nm.

[0010] Preferably, the thickness of the silicon dioxide metasurface 2 is 20–50 nm and the width is 3–20 μm.

[0011] This invention also provides a method for preparing the hyperbolic metasurface described in the above technical solution:

[0012] When the substrate is not composed of silicon dioxide, the preparation method includes the following steps: low-pressure chemical vapor deposition of silicon dioxide on the substrate to form a silicon dioxide layer;

[0013] The silicon dioxide layer is etched to form a nanograting structure, resulting in a hyperbolic metasurface.

[0014] When the substrate is composed of silicon dioxide, the preparation method includes: directly etching on the substrate to form a nanograting structure to obtain a hyperbolic metasurface.

[0015] Preferably, the etching is electron beam etching or plasma etching.

[0016] The present invention also provides the application of the hyperbolic metasurface described in the above technical solution or the hyperbolic metasurface prepared by the preparation method described in the above technical solution in mid-infrared metasurface imaging or mid-infrared detectors.

[0017] This invention provides a hyperbolic metasurface based on silica, comprising a substrate 1 and a silica metasurface 2 located on the substrate 1; the silica metasurface 2 has a nanograting structure; the nanograting structure is composed of several strips of silica. The silica-based hyperbolic metasurface provided by this invention, with its nanograting structure composed of several strips of silica, can generate hyperbolic phonon polaritons in the 8–10 μm wavelength band, which is beneficial for focusing light energy to a specific area, achieving effective light compression. Furthermore, this wavelength band is located within an atmospheric window, enabling long-distance infrared thermal imaging, which helps improve the performance of photodetectors and mid-infrared metasurface imaging. Moreover, this metasurface has high integration density, facilitating photonic integration. The hyperbolic metasurface of this invention can be applied to mid-infrared metasurface imaging and light energy transmission devices, and can be fabricated into superlenses to focus light to a location smaller than the wavelength. The denser the focused light, the smaller the focal point, and the higher the image resolution, making it suitable for ultra-high-density integrated optical path design. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the hyperbolic metasurface structure in an embodiment of the present invention, where 1 is the substrate and 2 is the silicon dioxide metasurface;

[0019] Figure 2This is a schematic diagram of the hyperbolic metasurface in an embodiment of the present invention, wherein 2 is a silicon dioxide metasurface;

[0020] Figure 3 This is a near-field optical image of the hyperbolic metasurface in an embodiment of the present invention with a slit ratio of 40% under incident light from a 9.00 μm wavelength dipole light source.

[0021] Figure 4 This is a near-field optical image of the hyperbolic metasurface in an embodiment of the present invention with a slit ratio of 40% under incident light from a 9.13 μm wavelength dipole light source.

[0022] Figure 5 This is a near-field optical image of the hyperbolic metasurface in an embodiment of the present invention with a slit ratio of 30% under incident light from a 9.13 μm wavelength dipole light source.

[0023] Figure 6 This is a near-field optical image of the hyperbolic metasurface in an embodiment of the present invention with a slit ratio of 30% under incident light from a 9.23 μm wavelength dipole light source.

[0024] Figure 7 This is a near-field optical image of the hyperbolic metasurface in an embodiment of the present invention with a slit ratio of 20% under incident light from a 9.23 μm wavelength dipole light source.

[0025] Figure 8 This is a near-field optical image of the hyperbolic metasurface in an embodiment of the present invention, with the slit ratio being 20% ​​under incident light from a 9.31 μm wavelength dipole light source. Detailed Implementation

[0026] The present invention provides a hyperbolic metasurface based on silicon dioxide, comprising a substrate 1 and a silicon dioxide metasurface 2 located on the substrate 1; the silicon dioxide metasurface 2 has a nanograting structure; the nanograting structure is composed of a plurality of strips of silicon dioxide.

[0027] like Figure 1 As shown, the hyperbolic metasurface based on silicon dioxide provided by the present invention includes a substrate 1. In the present invention, the substrate is preferably made of silicon wafer or quartz wafer, more preferably silicon wafer; the length of the substrate is preferably 1-10 cm, more preferably 2-5 cm, and the width is preferably 1-10 cm, more preferably 2-5 cm.

[0028] like Figure 1 As shown, the hyperbolic metasurface based on silicon dioxide provided by the present invention includes a silicon dioxide metasurface 2 located on the substrate 1. In the present invention, the silicon dioxide metasurface 2 has a nanograting structure; the nanograting structure is composed of a plurality of strips of silicon dioxide, preferably 10 strips.

[0029] In this invention, the length of the strip-shaped silicon dioxide is preferably 5-20 μm, more preferably 10-15 μm, and the width is preferably 50-200 nm, more preferably 70-150 nm. The gap between the strip-shaped silicon dioxide is preferably 10-200 nm, more preferably 20-100 nm. The length of the gap between the strip-shaped silicon dioxide is the same as the length of the strip-shaped silicon dioxide.

[0030] In this invention, the slit ratio is defined as the width of the strip silica / (width of the strip silica + gap width between the strip silica) × 100%; the slit ratio is preferably 20-40%, more preferably 30%.

[0031] In this invention, the thickness of the silicon dioxide metasurface 2 is preferably 20-50 nm, more preferably 30-40 nm, and the width is preferably 3-20 μm, more preferably 5-15 μm.

[0032] The hyperbolic metasurface based on silicon dioxide provided by this invention has a nanograting structure composed of several strips of silicon dioxide. It can generate hyperbolic phonon polaritons in the 8-10 μm wavelength band, which is beneficial for focusing light energy to a specific area and achieving effective light compression. Moreover, this wavelength band is located in the atmospheric window, which can be used for long-distance infrared thermal imaging, which helps to improve the performance of photodetectors and mid-infrared metasurface imaging. In addition, the metasurface structure is small in size and highly integrated, thus facilitating photonic integration. The hyperbolic metasurface of this invention can be applied to metasurface imaging and light energy transmission devices, and can be made into superlenses to focus light to a location smaller than the wavelength. The more tightly focused the light is, the smaller the focal point, and the higher the image resolution, which is suitable for ultra-high density integrated optical path design.

[0033] This invention also provides a method for preparing the hyperbolic metasurface described in the above technical solution:

[0034] When the substrate is not composed of silicon dioxide, the preparation method includes the following steps: chemically vapor-depositing silicon dioxide on the substrate to form a silicon dioxide layer;

[0035] The silicon dioxide layer is etched to form a nanograting structure, resulting in a hyperbolic metasurface.

[0036] When the substrate is composed of silicon dioxide, the preparation method includes: directly etching on the substrate to form a nanograting structure to obtain a hyperbolic metasurface.

[0037] Unless otherwise specified, the present invention does not have special requirements on the source of raw materials used, and commercially available products well known to those skilled in the art can be used.

[0038] When the substrate is not composed of silicon dioxide, the present invention forms a silicon dioxide layer by low-pressure chemical vapor deposition of silicon dioxide on the substrate.

[0039] After forming a silicon dioxide layer, the present invention etches the silicon dioxide layer to form a nanograting structure, thereby obtaining a hyperbolic metasurface.

[0040] When the substrate is composed of silicon dioxide, the present invention directly etches on the substrate to form a nanograting structure, thereby obtaining a hyperbolic metasurface.

[0041] In this invention, the etching is preferably performed by electron beam lithography and plasma etching.

[0042] The present invention also provides the application of the hyperbolic metasurface described in the above technical solution or the hyperbolic metasurface prepared by the preparation method described in the above technical solution in mid-infrared metasurface imaging or mid-infrared detectors.

[0043] The present invention does not impose any particular limitation on the application of the hyperbolic metasurface in metasurface imaging or mid-infrared detectors; any application method known in the art can be used.

[0044] Under excitation by a dipole light source with an incident wavelength of 8–10 μm, the hyperbolic metasurface provided by this invention can generate hyperbolic phonon polaritons, exhibiting strong mode field confinement capabilities and achieving effective light compression. By changing the wavelength and the ratio of the width of the striped silica to the gap between the striped silica, the desired hyperbolic surface light field can be generated, and the desired electromagnetic wavefront can be obtained. Therefore, the silica-based hyperbolic metasurface can be applied to the fields of metasurface imaging and infrared detectors.

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0046] Example 1

[0047] The present invention provides a hyperbolic metasurface based on silicon dioxide, comprising a substrate and a silicon dioxide metasurface. The silicon dioxide metasurface is on the substrate (2 cm long and 2 cm wide), and the silicon dioxide metasurface has a nanograting structure. The nanograting structure is composed of 10 strips of silicon dioxide, each strip having a length of 10 μm, a width of 75 nm, and a gap of 50 nm between the strips. The sum of the width of the strips and the gaps is 125 nm, i.e., the slit ratio is 40%. The silicon dioxide metasurface has a thickness of 30 nm and a width of 10 μm.

[0048] The preparation method is as follows: silicon dioxide is chemically vapor-deposited onto a substrate to form a silicon dioxide layer; the silicon dioxide layer is subjected to electron beam exposure and plasma etching to form a nanograting structure, thereby obtaining a hyperbolic metasurface.

[0049] Example 2

[0050] The difference from Example 1 is that the width of the strip silicon dioxide is 87.5 nm, the gap between the strip silicon dioxide is 37.5 nm, and the sum of the width and the gap of the strip silicon dioxide is 125 nm, that is, the slit ratio is 30%. The rest is the same as Example 1.

[0051] Example 3

[0052] The difference from Example 1 is that the width of the strip-shaped silicon dioxide is 100nm, the gap between the strip-shaped silicon dioxide is 25nm, and the sum of the width and gap of the strip-shaped silicon dioxide is 125nm, that is, the slit ratio is 20%. The rest is the same as Example 1.

[0053] Performance testing:

[0054] The relative permittivity of the silicon dioxide layer in Example 1 was calculated using the following formula: ε Lorentz (ω)=ε ∞ +Ω 2 / (ω 2 TO -ω 2 -iγω), where ε ∞ =2.14, Ω=950cm -1 γ = 10cm -1 ω TO =1064cm -1 .

[0055] The results show that the relative permittivity of silicon dioxide is ε = -6.25 + 1.82i at 9.00 μm, ε = -9.91 + 3.89i at 9.13 μm, ε = -14.83 + 8.77i at 9.23 μm, and ε = -18.85 + 20.63i at 9.31 μm.

[0056] The silicon dioxide layer of Example 1 was etched to obtain a silicon dioxide hyperbolic metasurface. The equivalent relative permittivity of the silicon dioxide hyperbolic metasurface was calculated using the following formula: ε eff,x =1 / ((1-ζ) / ε+ζ), ε eff,y =ε*(1-ζ)+ζ, ζ=g / (g+w), where ζ is the slit ratio, g is the gap between the strips of silica, and w is the width of the strips of silica. The result is as follows Figures 3-8 As shown.

[0057] Depend on Figure 3 and 4 It can be seen that the width of the strip-shaped silica is 75 nm, and the gap between the strip-shaped silica is 50 nm. That is, when the slit ratio is 40%, the ε at 9.00 μm is... eff,x =3.2+0.3i, ε eff,y = -3.4 + 1.1i; ε is 9.13 μm and the slit ratio is 40%. eff,x =2.9+0.2i, ε eff,y = -5.6 + 2.4i.

[0058] Depend on Figure 5 and 6 It can be seen that when the width of the striped silicon dioxide is 87.5 nm and the gap between the striped silicon dioxide is 37.5 nm, that is, when the slit ratio is 30%, the equivalent relative permittivity of the silicon dioxide hyperboloid metasurface is ε at 9.13 μm. eff,x =4.1+0.4i,ε eff,y = -6.7 + 2.8i; ε at 9.23 μm eff,x =3.7+0.3i,ε eff,y = -10.2 + 6.3i.

[0059] Depend on Figure 7 and 8 It can be seen that when the width of the striped silica is 100 nm and the gap between the striped silica is 25 nm, that is, when the slit ratio is 40%, the equivalent relative permittivity of the silica hyperboloid metasurface is ε at 9.23 μm. eff,x =6.8+0.9i,ε eff,y = -11 + 7.2i; ε at 9.31 μm eff,x =5.44+0.6i, ε eff,y = -14.9 + 17i.

[0060] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A hyperbolic metasurface based on silica, comprising a substrate (1) and a silica metasurface (2) located on the substrate (1), characterized in that, The silica metasurface (2) has a nanograting structure; the nanograting structure is composed of several strips of silica. The strip-shaped silica has a length of 5~20μm and a width of 50~200nm; The gaps between the strip-shaped silicon dioxide are 10~200 nm; The thickness of the silicon dioxide metasurface (2) is 20~50nm and the width is 3~20μm; The substrate is made of silicon wafer or quartz wafer; The preparation method of the hyperbolic metasurface: When the substrate is not composed of silicon dioxide, the preparation method includes the following steps: depositing silicon dioxide on the substrate by low-pressure chemical vapor deposition to form a silicon dioxide layer; The silicon dioxide layer is etched to form a nanograting structure, resulting in a hyperbolic metasurface. When the substrate is composed of silicon dioxide, the preparation method includes: directly etching on the substrate to form a nanograting structure to obtain a hyperbolic metasurface.

2. The method for preparing the hyperbolic metasurface according to claim 1, characterized in that: When the substrate is not composed of silicon dioxide, the preparation method includes the following steps: depositing silicon dioxide on the substrate by low-pressure chemical vapor deposition to form a silicon dioxide layer; The silicon dioxide layer is etched to form a nanograting structure, resulting in a hyperbolic metasurface. When the substrate is composed of silicon dioxide, the preparation method includes: directly etching on the substrate to form a nanograting structure to obtain a hyperbolic metasurface.

3. The preparation method according to claim 2, characterized in that, The etching is performed by electron beam exposure and plasma etching.

4. The application of the hyperbolic metasurface according to claim 1 or the hyperbolic metasurface prepared by the preparation method according to any one of claims 2 to 3 in mid-infrared metasurface imaging or mid-infrared detectors.

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