High-speed light beam scanning device based on two-dimensional dynamic adjustable metasurface

Abstract

The invention discloses a high-speed light beam scanning device based on a two-dimensional dynamic adjustable metasurface. The unit structure of the device is composed of a bottom metal electrode backboard, a P-type semiconductor, an insulating medium, an ITO film and a gold metasurface. The working wavelength of the unit structure is determined by F-P resonance, and the carrier concentration at the interface of the P-type semiconductor, the ITO thin film and the insulating medium can be changed through a field effect by applying voltage to the two ends, so that the dielectric constant at the interface is changed to enter an ENZ region, and the reflectivity and phase mutation at the working wavelength are changed. The two-dimensional pixelated spatial light modulator is realized by spatially pixelating the bottom metal electrode back plate, and two-dimensional high-speed spatial light modulation can be realized by applying gradient voltage to each unit structure to generate different gradient phases. The invention provides a design method of an electrically tunable metasurface spatial light modulator capable of realizing high-speed light beam scanning.

Description

Technical Field

[0001] The present invention relates to the technical field of light field control devices, and in particular to a light beam scanning device based on a two-dimensional dynamically adjustable metasurface. Background Art

[0002] With the continuous development of optical technology, beam scanning systems are increasingly being used in fields such as LiDAR, optical communications, virtual reality (VR), and augmented reality (AR). These fields place higher demands on beam scanning equipment, including two-dimensional modulation, faster scanning speeds, higher resolution, a larger field of view, and a more compact and lightweight design. However, traditional beam scanning systems mainly rely on mechanical scanning modules. Although these mechanical systems can achieve a large scanning range, they are bulky, power-hungry, slow to respond, and their complex mechanical structures are prone to wear, making them unable to meet the high-performance and miniaturization requirements of modern optical systems.

[0003] Liquid crystal optical phased arrays (LCAOs) have garnered widespread attention as a fully solid-state beam scanning method. LCAO technology enables real-time, precise control of beam scanning and is compatible with two-dimensional beam scanning. It boasts advantages such as low drive voltage, high scanning accuracy, random pointing, real-time programmability, compact size, and low power consumption. However, due to the fringe field effect of liquid crystals, the phased array unit cannot be effectively reduced, limiting the beam scanning angle. Furthermore, the modulation speed of LCAO is limited, making it difficult to meet high-speed requirements exceeding MHz.

[0004] In recent years, the rise of metasurface technology has provided a novel solution for beam scanning systems. Metasurfaces are artificial two-dimensional materials composed of subwavelength-scale nanostructured units. By manipulating subwavelength localized light fields, metasurfaces not only enable larger beam scanning angles, faster response speeds, and lower power consumption, but also significantly reduce device size, opening up new possibilities for improving traditional beam scanning systems. These nanostructured units can precisely control the phase, amplitude, and polarization of light waves, allowing the beam to be deflected or focused in space as needed.

[0005] In the near-infrared region, ITO can exhibit a near-zero dielectric constant (ENZ) effect, which can be used to control the phase, polarization, and amplitude of light fields in the near-infrared band. The realization of optical scanning relies on phase and amplitude control. In 2016, Huang et al. used metal gratings and ITO films to achieve phase modulation. In 2021, Park et al. used dual gate voltages to control the carrier concentration of ITO films, achieving independent control of phase and amplitude. The structure they designed can achieve a 360° phase modulation range at near-infrared wavelengths, verifying the high-speed one-dimensional beam scanning function. However, this structure can only achieve one-dimensional control of the light beam, and its two-dimensional control is limited by the complexity of two-dimensional wiring.

[0006] To address these issues, this paper proposes a spatial light modulator based on a two-dimensional dynamically tunable metasurface. Unlike liquid crystal phased arrays, this approach leverages the metasurface's localized light field manipulation effect, theoretically enabling the realization of submicron pixel arrays. Combining a two-dimensional surface with vertical wiring allows for independent electrical control of two-dimensional pixels. This enables high-speed two-dimensional light field manipulation, which has important applications in high-speed, complex light field manipulation applications such as lidar and optical communications.

[0007] The information disclosed in this background section is only intended to enhance understanding of the overall background of the invention and should not be considered as an admission or any form of suggestion that the information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0008] The present invention solves the technical problems mentioned in the background through the following technical means: a high-speed beam scanning device based on a two-dimensional dynamically adjustable metasurface is proposed, which can improve the phase and amplitude modulation depth under a single electrode, simplify the wiring difficulty, and thus realize the independent adjustment of the two-dimensional array unit.

[0009] The object of the present invention is achieved through the following technical solutions: a high-speed beam scanning device based on a two-dimensional dynamically adjustable metasurface, the device consisting of a bottom metal electrode backplane, a P-type semiconductor layer, an insulating layer, an ITO layer and a gold metasurface from bottom to top;

[0010] The P-type semiconductor layer, insulating layer and ITO layer constitute a modulation dielectric layer, and the bottom metal electrode backplane-modulation dielectric layer-gold supersurface constitutes a MIM nanoresonant cavity; by applying voltage to the gold supersurface layer and the bottom metal backplane layer, the carrier concentrations of the two double interfaces of ITO-insulating layer and P-type semiconductor-insulating layer are modulated simultaneously, entering the ENZ region, thereby changing the dielectric constants at the two interfaces and realizing dynamic modulation of the phase of the incident light field.

[0011] Furthermore, the bottom metal electrode backplane is used for electrical connection and to improve reflectivity;

[0012] Furthermore, the bottom metal electrode back plate is made of aluminum or gold.

[0013] Furthermore, the P-type semiconductor material is Si or PEDOT:PASS semiconductor material.

[0014] Furthermore, the insulating layer is made of Al2O3 or HfO2 material.

[0015] Furthermore, the thickness of the insulating layer material is 5 nm to 20 nm.

[0016] Furthermore, the carrier concentration of the ITO layer needs to ensure that the real part of the ITO dielectric constant at the design wavelength is in the range of 1.5 to 2.5, and the corresponding carrier concentration is on the order of 10 19 ~10 21 cm -3 .

[0017] Furthermore, the bottom metal electrode backplane adopts a pixelated electrode backplane design, and ultra-surface processing is achieved through a layered coating process, and the top electrode adopts a transparent conductive electrode.

[0018] Furthermore, the pixel electrode backplane has the function of independently controlling the voltage of individual pixels, that is, integrating the driving circuit into the backplane with pixel transistors; the pixel electrode voltage control range and control speed need to match the phase modulation capability of the spatial light modulator.

[0019] Beneficial effects of the present invention:

[0020] The present invention proposes a high-speed beam scanning device based on a two-dimensional dynamically adjustable metasurface. The phase control unit can achieve sub-micron pixels, effectively improving the sampling rate of light field control and supporting the realization of ultra-large field of view angle control. The use of a dual ENZ mode can effectively improve the efficiency of light field control. The dual ENZ mode generated by a single electrode can increase the phase and amplitude modulation depth. Technically, it can effectively reduce the difficulty of wiring. On this basis, the two-dimensional structural design of the upper and lower electrodes proposed in the present invention can reduce the area occupied by the metasurface wiring, effectively increase the metasurface modulation duty cycle, reduce sidelobe loss, and further improve the efficiency of light field modulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 is a structural diagram of a dual ENZ unit according to an embodiment of the present invention;

[0023] Figure 2 is a two-dimensional structural diagram of an embodiment of the present invention;

[0024] Figure 3 is a longitudinal cross-sectional view of a two-dimensional structure according to an embodiment of the present invention;

[0025] Figure 4 2 is a schematic diagram of an application of a two-dimensional dynamically adjustable metasurface according to an embodiment of the present invention;

[0026] Reference numerals in the figure: 401: transparent conductive top electrode; 402: metasurface antenna layer; 403: ITO layer; 404: insulating layer; 405: P-type semiconductor; 406: bottom electrode; 407: substrate; DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0028] The present invention provides a high-speed beam scanning device based on a two-dimensional dynamically adjustable metasurface. The device comprises, from bottom to top, a bottom metal electrode backplane, a P-type semiconductor layer 405, an insulating layer 404, an ITO layer 403, and a gold metasurface. The bottom metal electrode backplane includes a substrate 407 and a bottom electrode 406, while the gold metasurface includes a metasurface antenna layer 402 and a transparent conductive top electrode 401.

[0029] The P-type semiconductor layer 405, insulating layer 404, and ITO layer 403 form a modulation dielectric layer, while the bottom metal electrode backplane, modulation dielectric layer, and gold metasurface form a MIM nanoresonant cavity. By applying voltage to the gold metasurface layer and the bottom metal electrode backplane, the carrier concentrations at both the ITO-insulating layer and P-type semiconductor-insulating layer interfaces can be modulated simultaneously, entering the ENZ region and thereby changing the dielectric constant at the interfaces, ultimately achieving dynamic modulation of the incident light field phase.

[0030] The carrier concentration of the ITO layer 403 needs to ensure that the real part of the ITO dielectric constant at the design wavelength is in the range of 1.5 to 2.5. The corresponding carrier concentration is on the order of 10 19 ~10 21 cm -3 : The P-type semiconductor material can be Si, PEDOT:PASS or other hole-type heavily doped semiconductor materials; the insulating layer 404 material can be Al2O3, HfO2 or other high dielectric materials, and the thickness of the insulating layer material needs to be thick enough to prevent voltage breakdown, generally 5nm to 20nm;

[0031] The bottom metal electrode backplane is used for electrical connection and to improve reflectivity. The bottom metal electrode backplane can be made of materials with high reflectivity in the operating band, such as aluminum and gold.

[0032] The present invention also proposes a corresponding two-dimensional wiring scheme: a pixelated electrode backplane design, a layered coating process to achieve super-surface processing, and a transparent conductive electrode as the top electrode. The pixelated electrode backplane must maintain a sufficiently high duty cycle to improve the efficiency of light field modulation.

[0033] The pixel electrode backplane has the function of independently controlling the voltage of each pixel. This means that due to the limitations of the spatial light modulator's pixel size and cost, the driving circuit is integrated into the backplane with pixel transistors. The pixel electrode voltage control range and control speed must match the phase modulation capability of the spatial light modulator.

[0034] Example 1:

[0035] The structure of a single-pixel metasurface is as follows Figure 1 As shown. From bottom to top, the layers are the bottom electrode, P-type semiconductor layer, insulating layer, ITO layer and super surface layer. The bottom electrode is the array pixel, the material is Al, and the thickness is 80nm. The thickness of the P-type semiconductor layer is 10nm, and the insulating layer is aluminum oxide grown by atomic layer deposition with a thickness of 10nm to ensure that a voltage within ±8V can be applied. The thickness of the ITO layer is about 10nm. Under the condition of applying the same voltage, the carrier concentrations at the interfaces between the P-type semiconductor and the insulating layer, and the ITO and the insulating layer are modulated respectively to form a double ENZ interface. Compared with the single ENZ structure, the modulation layer of this structure is doubled, so higher light field modulation efficiency can be achieved.

[0036] Example 2:

[0037] The structure of the array metasurface is as follows Figure 2 As shown. It includes a silicon crystal backplane, a bottom electrode (voltage applied), a P-type semiconductor layer, an insulating layer, an ITO layer, a super surface layer, and a transparent conductive electrode (grounded). The bottom electrode is an array pixel, the material is Al, the thickness is 80nm, the bottom electrodes are electrically isolated from each other, and independent control voltage can be applied. The period of the bottom electrode is 3.74μm. The thickness of the P-type semiconductor layer is 10nm, and the insulating layer is aluminum oxide grown by atomic layer deposition with a thickness of 10nm to ensure that a voltage within ±8V can be applied. The thickness of the ITO layer is about 10nm. The spacing between the upper and lower electrodes is 40nm, and the edge field effect is small. Figure 3 This is a cross-sectional view of the array metasurface. Furthermore, due to the high-speed characteristics of carrier concentration regulation, modulation speeds exceeding 1 MHz can be guaranteed.

[0038] Example 3:

[0039] Figure 4This is a schematic diagram of the application of a beam scanning device for a two-dimensional dynamically adjustable metasurface. The system demonstrates the application of a lidar, which includes a laser light source, a spatial light modulator for two-dimensional modulation of the reflected light, a detection target, and a laser receiving system. The two-dimensional active metasurface can be loaded with blazed gratings and vortex phases to achieve angle scanning and enhance the detection signal-to-noise ratio. The pixel size of the two-dimensional active metasurface is p, the blazed grating period is N, and the beam scanning angle that can be achieved is

[0040]

[0041] The above embodiments are used to illustrate the present invention rather than to limit the present invention. Any modifications and changes made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A high-speed beam scanning device based on a two-dimensional dynamically adjustable metasurface, characterized in that: From bottom to top, the device consists of a bottom metal electrode backplane, a P-type semiconductor layer, an insulating layer, an ITO layer, and a gold metasurface. The P-type semiconductor layer, insulating layer and ITO layer constitute a modulation dielectric layer, and the bottom metal electrode backplane-modulation dielectric layer-gold supersurface constitutes a MIM nanoresonant cavity; by applying voltage to the gold supersurface layer and the bottom metal backplane layer, the carrier concentrations of the two double interfaces of ITO-insulating layer and P-type semiconductor-insulating layer are modulated simultaneously, entering the ENZ region, thereby changing the dielectric constants at the two interfaces and realizing dynamic modulation of the phase of the incident light field.

2. The high-speed beam scanning device based on a two-dimensional dynamically adjustable metasurface according to claim 1, characterized in that: The bottom metal electrode backplane is used for electrical connection and to improve reflectivity.

3. The high-speed beam scanning device based on a two-dimensional dynamically adjustable metasurface according to claim 1, characterized in that: The bottom metal electrode backplate is made of aluminum or gold.

4. The high-speed beam scanning device based on a two-dimensional dynamically adjustable metasurface according to claim 1, characterized in that: The P-type semiconductor material is Si or PEDOT:PASS semiconductor material.

5. The high-speed beam scanning device based on a two-dimensional dynamically adjustable metasurface according to claim 1, characterized in that: The insulating layer is made of Al2O3 or HfO2 material.

6. The high-speed beam scanning device based on a two-dimensional dynamically adjustable metasurface according to claim 1, characterized in that: The thickness of the insulating layer material is 5 nm to 20 nm.

7. The high-speed beam scanning device based on a two-dimensional dynamically adjustable metasurface according to claim 1, characterized in that: The carrier concentration of the ITO layer needs to ensure that the real part of the ITO dielectric constant at the design wavelength is in the range of 1.5 to 2.5, and the corresponding carrier concentration is on the order of 10 19 ~10 21 cm -3 .

8. The high-speed beam scanning device based on a two-dimensional dynamically adjustable metasurface according to claim 1, characterized in that: The bottom metal electrode backplane adopts a pixelated electrode backplane design, achieves ultra-surface processing through a layered coating process, and the top electrode adopts a transparent conductive electrode.

9. The high-speed beam scanning device based on a two-dimensional dynamically adjustable metasurface according to claim 8, characterized in that: The pixel electrode backplane has the function of independently controlling the voltage of individual pixels, that is, integrating the driving circuit into the backplane with pixel transistors; the pixel electrode voltage control range and control speed need to match the phase modulation capability of the spatial light modulator.

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