Hydrogel super-structure grating for realizing dynamic wavelength selective deflection and application of hydrogel super-structure grating

Abstract

The invention discloses a hydrogel super-structure grating for realizing dynamic wavelength selective deflection and application of the hydrogel super-structure grating. The hydrogel super-structure grating is formed by sequentially arranging a top layer metal film, a middle wedge-shaped hydrogel structure and a bottom layer metal film. The hydrogel super-structure grating integrates Fabry-Perot microcavity resonance and grating diffraction effects, when white light normally enters the hydrogel super-structure grating, an absorption peak exists at a resonant wavelength, meanwhile, light waves near the resonant wavelength are deflected to a diffraction order, light of other wavelengths is vertically reflected, and the function of wavelength selective deflection is achieved; by changing the environment humidity, the middle wedge-shaped hydrogel layer expands, the resonance wavelength of the hydrogel super-structure grating is effectively adjusted, and the functions of dynamic absorption and dynamic wavelength selective deflection can be achieved. The hydrogel super-structure grating provided by the invention realizes wavelength selective deflection, has dynamic characteristics, and can be widely applied to the fields of dynamic optical filtering, gas sensing, optical imaging and the like.

Description

Technical Field

[0001] The present invention relates to the field of nanophotonics and optical devices, and in particular to a hydrogel metagrating for realizing dynamic wavelength selective deflection and an application thereof. Background Art

[0002] Traditional optical devices usually have fixed optical properties and cannot adapt to dynamically changing environments or application requirements. In recent years, with the development of materials science and micro-nano processing technology, tunable optical devices based on active materials have received widespread attention. Active materials, such as liquid crystals, phase change materials, conductive polymers, etc., show changes in optical properties due to their response to external stimuli (such as electric fields, temperature, humidity, etc.), which provides the possibility of realizing dynamically adjustable optical devices. In particular, the Fabry-Perot (FP) resonant cavity has been widely studied due to its simple structure and flexible regulation. The FP resonant cavity can achieve the regulation of the resonant wavelength by adjusting the thickness of the medium in the cavity, thus showing application potential in the fields of optical filtering and sensors. However, existing devices based on the FP resonant cavity mostly use solid-state active materials, and their regulation speed and range are subject to certain limitations. In addition, it is still a technical challenge to integrate multiple physical mechanisms into one device to achieve multifunctional regulation. As a soft material with high humidity responsiveness, hydrogels show great potential in adjustable optical devices due to their unique expansion-contraction properties. However, how to effectively combine hydrogels with micro-nano optical structures to realize dynamic functional integrated devices is a key issue that needs to be solved in the development of new active optical devices. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention proposes a hydrogel-based metagrating device with dynamic wavelength selective beam steering and tunable absorption characteristics that combines Fabry-Perot (FP) resonance and diffraction effect. The device utilizes the shrinkage characteristics of hydrogel under electron beam exposure and realizes the manufacture of hydrogel metagrating through direct patterning technology. And based on the humidity-responsive expansion characteristics of the hydrogel material, dynamic wavelength selective control of the beam is achieved.

[0004] To achieve the above object, the technical solution of the present invention is as follows:

[0005] In a first aspect, the present invention provides a hydrogel metagrating that realizes dynamic wavelength selective deflection, wherein the hydrogel metagrating is composed of a three-layer structure of a top metal film, a middle wedge-shaped hydrogel structure, and a bottom metal film arranged in sequence.

[0006] As a preferred solution, the metal of the top metal film-the middle wedge-shaped hydrogel structure-the bottom metal film is gold or silver; the hydrogel layer is any one of polyvinyl alcohol (PVA), polyacrylic acid PAA or polymethacrylic acid PMAA, and has humidity-responsive expansion characteristics;

[0007] The top metal film-middle wedge-shaped hydrogel structure-bottom metal film structure are all sub-wavelength in size.

[0008] The hydrogel layer utilizes the polymer shrinkage characteristics under electron beam exposure. The thickness of the hydrogel layer is controlled by adjusting the dose of electron beam exposure to achieve precise preparation of the middle wedge-shaped hydrogel layer.

[0009] Realize the function of dynamic wavelength selective deflection: when white light is incident on the hydrogel metagrating, there is an absorption peak at the resonance wavelength. At the same time, the light waves near the resonance wavelength will be deflected to the diffraction order, and the light of other wavelengths will be reflected vertically, realizing wavelength selective deflection; by changing the ambient humidity, the function of dynamic wavelength selective deflection can be realized as the resonance wavelength moves.

[0010] In a second aspect, the present invention provides applications of the hydrogel metagrating, including the following aspects:

[0011] Optical filtering, using the tunable absorption properties of the metagrating to selectively filter light of a specific wavelength;

[0012] Gas sensing, detecting gas composition by monitoring the response of the metagrating device to a specific gas;

[0013] Optical imaging, using the wavelength-selective beam steering properties of the metagrating to achieve dynamic imaging.

[0014] The hydrogel metagrating in the present invention can not only realize wavelength selective deflection, but also perform dynamic absorption. Its integrated multifunctionality enables it to be applied to multiple fields such as optical filtering, gas sensing, and optical imaging.

[0015] The present invention realizes dynamic wavelength selective deflection of specific wavelength light in white light by combining Fabry-Perot (FP) resonance and grating diffraction effect. This deflection is dynamic and can be adjusted by changing the ambient humidity. The hydrogel layer has humidity-responsive expansion characteristics, and can dynamically adjust the resonance cavity length by changing the ambient humidity, realize dynamic control of the resonance absorption peak, and has dynamic adjustability.

[0016] The advantages and beneficial effects of the present invention are as follows:

[0017] 1. By combining Fabry-Perot (FP) resonance and diffraction effects, the hydrogel metagrating of the present invention can realize dynamic manipulation of absorption and wavelength selective deflection in a single device, and is a new type of active functional integrated micro-nano optical device.

[0018] 2. The expansion and contraction of the hydrogel layer responds quickly to changes in environmental humidity. The absorption peak wavelength of the present invention can be quickly adjusted, which is suitable for applications that require rapid light response. The absorption peak wavelength of the hydrogel metagrating can achieve a dynamic adjustment range, which makes it possible to finely control the spectrum.

[0019] 3. Compared with traditional photonic devices, hydrogel materials are less expensive, and direct patterning technology reduces manufacturing steps, which helps reduce overall costs. Because direct patterning technology is compatible with existing semiconductor lithography technology, it helps to achieve large-scale production of meta-gratings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a functional schematic diagram of the active regulation effect of the change of cavity length caused by the expansion of hydrogel on the diffraction wavelength in the present invention;

[0021] Figure 2 It is a schematic diagram of directly manufacturing a hydrogel metagrating by using grayscale electron beam lithography technology in the present invention;

[0022] Figure 3 It is an angular resolved diffraction simulation diagram of a hydrogel metagrating with a period of 1800 nm when the hydrogel thickness t is 380 nm and 450 nm in an embodiment of the present invention;

[0023] Figure 4 It is a simulation diagram corresponding to the reflection of the hydrogel metagrating at relative humidity of 50% and 65% and the simulated reflection at different hydrogel thicknesses in an embodiment of the present invention;

[0024] Figure 5 is a schematic diagram of the diffraction intensity corresponding to the resonance wavelength when the hydrogel thickness t is 380 nm and 450 nm in an embodiment of the present invention;

[0025] Figure 6 Schematic diagram of wavelength selective beam control switching of gratings under different humidity conditions in an embodiment of the present invention;

[0026] In the figure: t is the thickness of the middle wedge-shaped hydrogel layer, Δt is the thickness difference of the middle wedge-shaped hydrogel layer, and p is the period of the hydrogel metagrating. DETAILED DESCRIPTION

[0027] In order to more clearly illustrate the structure of the present invention and the functions it realizes, the present invention is further described below with reference to specific embodiments in conjunction with the accompanying drawings.

[0028] Example 1

[0029] A hydrogel metagrating was designed, which consists of a three-layer structure of a top silver film, a middle wedge-shaped hydrogel structure and a bottom silver film, in which the middle layer is made of polyvinyl alcohol (PVA). Figure 1 Due to the expansion of the hydrogel layer, the resonant absorption peak of the hydrogel metagrating will be dynamically adjusted with the change of the relative humidity (RH) of the environment. Due to the frequency-dependent resonance of the FP cavity, the hydrogel metagrating has a strong phase modulation capability at the resonant wavelength, and the light near the resonant wavelength is deflected to a specific angle. In contrast, light of other wavelengths is reflected vertically under normal incidence conditions. Through grayscale electron beam exposure technology, using the gradient distribution of exposure dose layout, it is possible to directly prepare a hydrogel metagrating with a blazed grating profile, such as Figure 2 In order to study the tunable optical properties of the hydrogel metagrating, the present invention simulated and calculated the angular resolved reflection of the metagrating with a period of 1800nm ​​at different hydrogel layer thicknesses of 380nm and 450nm, and the thickness difference Δt of the middle wedge-shaped hydrogel layer was set to 25nm, as shown in FIG. Figure 3 As shown. It can be observed that the light near the resonant wavelength is deflected to the diffraction order and the other light is reflected vertically, which reveals the successful combination of FP resonance and grating effect. The diffraction angle θ of the resonant wavelength can be calculated by the general law of grating reflection θ = arcsin (mλ / p), where m is the diffraction order, λ is the operating wavelength, and p is the grating period. In addition, the resonance shift caused by the expansion of the hydrogel layer can effectively adjust the operating wavelength of the hydrogel metagrating, providing feasibility for dynamic wavelength-selective beam control. In order to experimentally verify the dynamic characteristics of the hydrogel metagrating, this embodiment reveals its adjustable absorption and switchable beam control capabilities under different humidity conditions. Figure 4 The reflectivity change of the hydrogel metagrating measured by increasing the ambient humidity from about 50% to about 65% is consistent with the spectral change of the simulated hydrogel layer expanding from 380nm to 450nm, demonstrating that the hydrogel metagrating can effectively achieve dynamic spectral absorption modulation. In the experiment, the measured thickness difference Δt of the hydrogel metagrating is about 25nm, which is consistent with the simulation setting. Figure 3 According to the theoretical calculation in , when the thickness of the hydrogel layer expands from 380nm to 450nm, the diffraction working wavelength of the metagrating is actively adjusted from 660nm to 517nm, and the diffraction angle changes due to the grating dispersion. The angular resolved diffraction intensity distribution at the working wavelength is shown in Figure 5 shown. Figure 6The experimentally measured dynamic wavelength selective diffraction of the hydrogel metagrating is shown when the RH increases from about 50% to about 65%. Due to the change in the FP resonance wavelength, the diffraction intensity of the hydrogel metagrating switches between wavelengths of 660nm and 517nm with high contrast, which is consistent with the theoretical design results. Therefore, the ability of the hydrogel metagrating to dynamically deflect wavelength selectively is demonstrated.

[0030] The hydrogel-based metagrating device of the present invention realizes the preparation of the hydrogel metagrating by electron beam exposure, and realizes the dynamic regulation of FP resonance absorption by utilizing the humidity responsiveness of the hydrogel, thereby realizing wavelength selective beam steering and tunable absorption, providing a new type of dynamically adjustable optical solution for the field of nanophotonics. The hydrogel metagrating proposed in the present invention can effectively adjust the working wavelength and angle of diffraction by changing the ambient humidity, providing a new technical approach for the fields of optical display, gas sensing and spectral analysis.

Claims

1. A hydrogel metagrating for realizing dynamic wavelength selective deflection, characterized in that: The hydrogel metagrating consists of a three-layer structure of a top metal film, a middle wedge-shaped hydrogel structure, and a bottom metal film. By adjusting the ambient humidity, the middle wedge-shaped hydrogel layer of the hydrogel metagrating expands, which can effectively adjust the resonance cavity length and realize dynamic control of the resonance absorption peak and wavelength selective deflection.

2. The hydrogel metagrating according to claim 1, characterized in that: The hydrogel layer has dose-sensitive polymer shrinkage properties, which enables metagratings to be prepared by electron beam direct writing.

3. The hydrogel metagrating according to claim 2, characterized in that: The metals of the top metal film, the middle wedge-shaped hydrogel structure and the bottom metal film are all silver or gold; the hydrogel layer is any one of polyvinyl alcohol (PVA), polyacrylic acid (PAA) or polymethacrylic acid (PMAA).

4. The hydrogel metagrating according to claim 3, characterized in that: The top metal film-middle wedge-shaped hydrogel structure-bottom metal film structure are all sub-wavelength in size.

5. A use of the hydrogel metagrating as claimed in claim 3 in preparing an optical filter device, characterized in that: The optical filtering refers to utilizing the tunable absorption characteristics of the metagrating to selectively filter light of a specific wavelength.

6. An application of the hydrogel metagrating as claimed in claim 3 in preparing a body sensor device, characterized in that: The gas sensing refers to detecting environmental changes by monitoring the response of the metagrating device to humidity gas.

7. A use of the hydrogel metagrating as claimed in claim 3 in preparing an optical imaging device, characterized in that: The optical imaging refers to realizing dynamic imaging by utilizing the wavelength selective beam steering characteristics of the metagrating.

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