Dynamic adjustable holographic metasurface based on vanadium dioxide

Abstract

The invention discloses a dynamic adjustable holographic metasurface based on vanadium dioxide, and belongs to the technical field of optical holographic display. The holographic metasurface comprises holographic metasurface units which are periodically arranged in the horizontal direction. The holographic metasurface unit comprises a silicon substrate and a vanadium dioxide rectangular column, and an included angle is formed between the long side of the rectangular column and the transverse side of the substrate. According to the invention, the dynamic adjustable holographic metasurface with temperature control is realized, and the flexibility and the application range of holographic display are greatly improved; the characteristic that the conductivity of vanadium dioxide at different temperatures is remarkably different is utilized, so that the contrast ratio and the resolution ratio of holographic patterns are improved, and the display effect is excellent; according to the invention, the implementation of wearable augmented reality equipment, intelligent dynamic display equipment and the like is facilitated, meanwhile, a standard semiconductor process is adopted, the process technology is mature, the manufacturing cost is low, and large-scale manufacturing is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of optical holographic display, and in particular relates to a dynamically adjustable holographic metasurface based on vanadium dioxide. Background Art

[0002] "Hologram" refers to the amplitude and phase information of the light field. Holographic display technology can completely record and reconstruct holographic patterns. In holography, using the principles of interference and diffraction, this information can be recorded on a holographic plate and restored under specific reference light.

[0003] Optical metasurfaces are composed of many sub-wavelength periodic structural units. Encoding holographic information pixel by pixel on the structural units of the metasurface can suppress the multiple images and losses caused by high-order diffraction, thereby achieving high-quality wide-angle holography. However, like most optical devices, existing metasurfaces have fixed structures and functions after processing, which means that the holographic images they produce cannot be changed. Therefore, the emergence of dynamically adjustable metasurfaces provides a turning point for this dilemma. The modulation methods currently disclosed in the prior art include the introduction of electrodes, flexible substrates, and special materials such as liquid crystals, phase change materials, chemically active materials, and semiconductor multiple quantum wells. Due to the complexity of the system and the working characteristics of the introduced new materials, most modulated metasurfaces operate in longer bands. In view of the importance of the visible light band to holographic display technology, it is necessary to develop more modulation methods to solve the band limitations of existing methods.

[0004] In recent years, good results have been achieved in the field of metasurface holography. The Chinese patent application with application number 202410056666.2 and titled “A bidirectional holographic modulation method based on polarization-selective metasurface” achieves the technical effect that the reproduced image of the hologram can be observed only in the encrypted channel corresponding to a specific polarization and transmission direction. The Chinese patent application with application number 202410162813.4 and titled “A metasurface dynamic color holographic display method, system, device and medium” has a technical solution that can restore phase information from a theoretical level and can realize the function of holographic display with a large field of view. However, in the current research on metasurface holography, there are still some unclear technical routes for the application of actual metasurface materials and the combination of corresponding holographic algorithms. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a dynamically adjustable holographic metasurface based on vanadium dioxide, which realizes a holographic pattern in the visible light band. By utilizing the temperature-changing property of the phase change material vanadium dioxide, the dynamically adjustable property of the holographic metasurface is realized through the temperature control method, and it is expected to be applied in the fields of wearable augmented reality devices, intelligent dynamic displays, etc.

[0006] The technical problem proposed by the present invention is solved in this way:

[0007] A dynamically adjustable holographic metasurface based on vanadium dioxide comprises M×N holographic metasurface units periodically arranged in the horizontal direction, where M and N are positive integers respectively; the holographic metasurface unit comprises a substrate 1 and a rectangular column 2; the lower surface of the rectangular column 2 coincides with the upper surface of the substrate 1; the rectangular column 2 is coaxial with the substrate 1 in the vertical direction, and the long side of the rectangular column 2 forms an angle θ with the lateral side of the substrate 1, 0°≤θ≤180°; the period of the holographic metasurface unit is less than the wavelength of the incident light; the material of the substrate 1 is silicon, and the material of the rectangular column 2 is vanadium dioxide.

[0008] Furthermore, by configuring the angle θ in each holographic metasurface unit, the phase arrangement of the holographic metasurface is achieved, and when the incident light is incident on the holographic metasurface, a first target holographic pattern is obtained; the holographic metasurface is heated to obtain a second target holographic pattern.

[0009] Furthermore, the process of configuring the angle θ in each holographic metasurface unit is:

[0010] The curve relationship between the angle θ and the unit phase in the metasurface unit is extracted; the light field distribution of the first target holographic pattern is substituted into the GS iterative method to obtain the phase distribution of the first target holographic pattern; for each metasurface unit, the angle θ is mapped from the curve relationship according to the phase distribution of the first target holographic pattern at its corresponding position.

[0011] Furthermore, the electrical conductivity of vanadium dioxide varies with temperature. When the temperature is below 60 degrees Celsius, the electrical conductivity of the vanadium dioxide material is <1000S / m, and it is in an insulating state; when the temperature is above 60 degrees Celsius, the electrical conductivity of the vanadium dioxide material reaches about 10000S / m, and it is in a metallic state.

[0012] Furthermore, the temperature of the holographic metasurface is controlled by a thermoelectric cooler to achieve the conversion between the first target holographic pattern and the second target holographic pattern.

[0013] The present invention also provides a method for preparing a dynamically adjustable holographic supersurface based on vanadium dioxide, which comprises depositing a layer of vanadium dioxide on a silicon substrate layer by electron beam evaporation; spin-coating positive photoresist on the surface of the vanadium dioxide layer according to an angle θ, and exposing to obtain a rectangular column pattern corresponding to each holographic supersurface unit; after development, dry etching is performed by an inductively coupled plasma etcher to obtain each holographic supersurface unit.

[0014] The beneficial effects of the present invention are:

[0015] The present invention provides a dynamically adjustable holographic metasurface based on vanadium dioxide, which realizes a temperature-controlled dynamically adjustable holographic metasurface, greatly improving the flexibility and application scope of holographic display; the present invention utilizes the characteristic of significant difference in electrical conductivity of vanadium dioxide at different temperatures, so that the contrast and resolution of the holographic pattern are improved, and the display effect is excellent; the present invention is conducive to the realization of wearable augmented reality, intelligent dynamic display and other equipment, and at the same time adopts standard semiconductor processes, the process technology is mature, the manufacturing cost is low, and it is convenient for large-scale manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A top view of a holographic metasurface unit in the dynamically adjustable holographic metasurface of the present invention;

[0017] Figure 2 A three-dimensional structural diagram of a holographic metasurface unit in the dynamically adjustable holographic metasurface of the present invention;

[0018] Figure 3 is a phase distribution diagram of the holographic metasurface corresponding to the first target holographic pattern in the embodiment;

[0019] Figure 4 Schematic diagram of the arrangement of the holographic metasurface, the first target holographic pattern and the second target holographic pattern in the embodiment;

[0020] Figure 5 The phase curve diagram obtained by rotating the vanadium dioxide rectangular column 0-180° in the holographic metasurface described in the embodiment;

[0021] Figure 6 This is a curve diagram showing the change of conductivity of the vanadium dioxide material in the holographic supersurface as a function of temperature;

[0022] Figure 7 This is a flow chart of the preparation process of the holographic metasurface described in the embodiment. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0024] This embodiment provides a dynamically adjustable holographic metasurface based on vanadium dioxide, including M×N holographic metasurface units periodically arranged in the horizontal direction, where M and N are positive integers respectively; the top view and the three-dimensional structure diagram of the holographic metasurface unit are respectively as shown in Figure 1 and Figure 2 As shown, it includes a substrate 1 and a rectangular column 2; the lower surface of the rectangular column 2 coincides with the upper surface of the substrate 1; the rectangular column 2 and the substrate 1 are coaxial in the vertical direction, and the long side of the rectangular column 2 forms an angle θ with the lateral side of the substrate 1, 0°≤θ≤180°; the period of the holographic metasurface unit is smaller than the wavelength of the incident light; the material of the substrate 1 is silicon, and the material of the rectangular column 2 is vanadium dioxide.

[0025] In this embodiment, the length of the rectangular column 2 is L, the width is W and the height is H, all of which are in the sub-wavelength range and are determined by the wavelength of the laser light source used in the actual application. The arrangement period p of the holographic metasurface depends on the size and fineness of the hologram to be processed.

[0026] The phase arrangement of the holographic metasurface is achieved by configuring the angle θ in each holographic metasurface unit. When the incident light is incident on the holographic metasurface, the first target holographic pattern is obtained; the holographic metasurface is heated to obtain the second target holographic pattern.

[0027] In this embodiment, the process of configuring the angle θ in each holographic metasurface unit is:

[0028] The curve relationship between the angle θ and the unit phase in the metasurface unit is extracted; the light field distribution of the first target holographic pattern is substituted into the GS iterative method to obtain the phase distribution of the first target holographic pattern; for each metasurface unit, the angle θ is mapped from the curve relationship according to the phase distribution of the first target holographic pattern at its corresponding position.

[0029] like Figure 5 As shown in the phase curve diagram obtained by rotating the vanadium dioxide rectangular column by 0-180 degrees in this embodiment, the rotation angle of the vanadium dioxide rectangular column and the phase satisfy a two-fold relationship.

[0030] In this embodiment, the phase distribution diagram corresponding to the first target holographic pattern is as follows: Figure 3 As shown, it is a 16×16 phase distribution diagram, and the phase distribution diagram of the target holographic pattern is obtained by the GS iterative algorithm, where different grayscale colors represent different phase values.

[0031] like Figure 6 As shown, the conductivity of the vanadium dioxide material changes with temperature. When the temperature is below 60 degrees Celsius, the conductivity of the vanadium dioxide material is <1000S / m, which is in an insulating state; when the temperature is above 60 degrees Celsius, the conductivity of the vanadium dioxide material reaches about 10000S / m, which is in a metallic state. The temperature of the holographic metasurface is controlled by a thermoelectric cooler to achieve the conversion between the first target holographic pattern and the second target holographic pattern.

[0032] like Figure 4As shown, the phase distribution diagram of the first target holographic pattern is obtained by the GS iterative algorithm. The rectangular column 2 realizes different phases of the holographic metasurface unit structure by adjusting the angle θ of the vanadium dioxide rectangular column 2. The metasurface unit structure is arranged according to the phase distribution of the phase distribution diagram to realize the holographic metasurface arranged by geometric phase. When the incident light irradiates the holographic metasurface, the first target holographic pattern can be obtained. The holographic metasurface is placed on a thermoelectric cooler to achieve temperature control by heating or cooling; by heating, when the vanadium dioxide material of the rectangular column 2 is in a metallic state, the holographic metasurface can achieve a new phase distribution, obtain the second target holographic pattern, and realize the dynamic adjustability of the holographic metasurface.

[0033] The process flow chart of the dynamically adjustable holographic metasurface based on vanadium dioxide in the embodiment is as follows: Figure 7 As shown, the manufacturing is realized by standard photolithography process. First, a layer of vanadium dioxide is deposited on the silicon substrate by electron beam evaporation; then, a positive photoresist is spin-coated on the surface of the vanadium dioxide layer, and the required rectangular column pattern is obtained by exposure; after development, the vanadium dioxide rectangular column is obtained by dry etching using an inductively coupled plasma etcher.

[0034] The dynamically adjustable holographic metasurface based on vanadium dioxide described in this embodiment operates in the visible light band, and the holographic metasurface can be applied to wearable augmented reality devices, intelligent dynamic displays and other fields.

[0035] In the description of the present application, it should be understood that the terms "lateral", "upper", "lower", "vertical", "horizontal", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0036] The embodiments described above are only descriptions of the preferred methods of the present application, and are not intended to limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements made to the technical solutions of the present application by ordinary technicians in this field should fall within the protection scope determined by the claims of the present application.

Claims

1. A dynamically adjustable holographic metasurface based on vanadium dioxide, characterized in that: The invention comprises M×N holographic metasurface units which are periodically arranged in the horizontal direction, wherein M and N are respectively positive integers; the holographic metasurface unit comprises a substrate (1) and a rectangular column (2); the lower surface of the rectangular column (2) coincides with the upper surface of the substrate (1); the rectangular column (2) and the substrate (1) are coaxial in the vertical direction, and the long side of the rectangular column (2) forms an angle θ with the lateral side of the substrate (1), wherein 0°≤θ≤180°; the period of the holographic metasurface unit is less than the wavelength of the incident light; the substrate (1) is made of silicon, and the rectangular column (2) is made of vanadium dioxide.

2. The dynamically adjustable holographic metasurface based on vanadium dioxide according to claim 1, characterized in that: The phase arrangement of the holographic metasurface is achieved by configuring the angle θ in each holographic metasurface unit. When the incident light is incident on the holographic metasurface, the first target holographic pattern is obtained; the holographic metasurface is heated to obtain the second target holographic pattern.

3. The dynamically adjustable holographic metasurface based on vanadium dioxide according to claim 2, characterized in that: The process of configuring the angle θ in each holographic metasurface unit is: The curve relationship between the angle θ and the unit phase in the metasurface unit is extracted; the light field distribution of the first target holographic pattern is substituted into the GS iterative method to obtain the phase distribution of the first target holographic pattern; for each metasurface unit, the angle θ is mapped from the curve relationship according to the phase distribution of the first target holographic pattern at its corresponding position.

4. The dynamically adjustable holographic metasurface based on vanadium dioxide according to claim 1, characterized in that: The electrical conductivity of vanadium dioxide changes with temperature. When the temperature is lower than 60 degrees Celsius, the electrical conductivity of vanadium dioxide material is <1000S / m, and it is in an insulating state; when the temperature is higher than 60 degrees Celsius, the electrical conductivity of vanadium dioxide material reaches about 10000S / m, and it is in a metallic state.

5. The dynamically adjustable holographic metasurface based on vanadium dioxide according to claim 2, characterized in that: The temperature of the holographic metasurface is controlled by a thermoelectric cooler to achieve the conversion between the first target holographic pattern and the second target holographic pattern.

6. A method for preparing a dynamically adjustable holographic metasurface based on vanadium dioxide, used for preparing the holographic metasurface according to claim 1, characterized in that: A layer of vanadium dioxide is deposited on the silicon substrate layer by electron beam evaporation; a positive photoresist is spin-coated on the surface of the vanadium dioxide layer according to the angle θ, and a rectangular column pattern corresponding to each holographic metasurface unit is obtained by exposure; After development, each holographic metasurface unit is obtained by dry etching using an inductively coupled plasma etcher.

Images