Layered metamaterial-based electric control amplitude modulator and preparation method thereof

Abstract

The invention relates to the technical field of voltage regulation and control metamaterials, and discloses an electric control amplitude modulator based on a layered metamaterial and a preparation method of the electric control amplitude modulator. The layered metamaterial is formed by alternately growing doped semiconductors and intrinsic semiconductors, the outermost layer of the layered metamaterial is respectively linked with dielectric layers with the same thickness in the vertical layer direction, and the dielectric layers are respectively connected with metal polar plates. Incident light is emitted to the structure along the direction of a parallel layer. In the layered structure, the conductivity of the whole metamaterial can be changed by forward or reverse direct-current voltage applied to the metal pole plates, so that the modulator only changes the intensity of reflected or transmitted light without changing the phase of the modulator.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular provides an electrically controlled electromagnetic wave amplitude modulator based on layered metamaterials and a preparation method thereof. Background Art

[0002] Precise manipulation of electromagnetic waves through advanced nanoscale engineering not only overcomes the limitations of conventional optical devices, but also ensures alignment with the needs of emerging application areas. Metasurfaces, characterized by arrays of subwavelength nanostructures called meta-atoms, have an impressive ability to precisely and efficiently tailor incident light. With a wide range of manipulation capabilities including polarization, phase, amplitude, and frequency, metasurfaces are becoming increasingly influential in a variety of functions and applications, including high numerical aperture achromatic lenses, miniaturized optical anti-counterfeiting devices, optical analog computers, and real-time biochemical sensors. Metamaterials and metasurfaces exhibit a variety of exotic optical properties such as photomagnetism, negative refraction, sub-diffraction imaging, and stealth. These materials are the focus of current research not only for their interest, but also for their potential for a wide range of applications such as optical switches, modulators, filters, and phase shifters.

[0003] Most modulatable modulation devices change the photoelectric amplitude and phase simultaneously when adjusting their reflection and transmission properties. In contrast, this patent does not change the phase of the reflected and transmitted light when modulating incident light of a specific wavelength. Compared with ordinary modulation devices, this purely intensity-controlled modulation device has higher flexibility and freedom, reducing the need for additional processing due to phase changes. This uniqueness and diversity of application scenarios provide us with more efficient and economical solutions. Secondly, it has a higher transmittance. For example, in some designs, the transmittance can be as high as 97%, which is much higher than the transmittance of traditional silicon-based lenses, conical lenses, and blazed gratings. In addition, purely intensity-controlled modulation devices can achieve more efficient light energy utilization and better focusing effects, and the peak intensity is significantly improved compared to traditional devices. For example, in some cases it can be increased by 1.64 to 3.77 times. Summary of the invention

[0004] In view of this, in view of the defects of the prior art, the present invention proposes an electrically controlled amplitude modulator based on layered metamaterials. In this layered metamaterial, applying a forward or reverse bias voltage can change the carrier concentration and distribution and conductivity of the doped semiconductor region without changing its relative dielectric constant and magnetic permeability, thereby realizing an amplitude modulator.

[0005] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme to achieve it: an electrically controlled amplitude modulator based on layered metamaterial, comprising a layered metamaterial, a dielectric layer and a metal electrode. The layered metamaterial is composed of layered intrinsic semiconductors and layered doped semiconductors alternately stacked, the doped semiconductor layer and the half intrinsic semiconductor layer connected on both sides are a periodic unit, and the thickness of the periodic unit in the vertical plane direction is the periodic unit thickness; the outermost layers of the layered metamaterial in the vertical plane direction are respectively connected to dielectric layers of the same thickness, and the thickness of the dielectric layer is greater than the periodic unit thickness. The dielectric layers are respectively connected to the metal electrodes. The working electromagnetic wave is incident in a direction parallel to the plane and perpendicular to the surface of the layered metamaterial.

[0006] The present invention applies voltage between metal plates to change the concentration and distribution of carriers in the doped semiconductor, thereby changing the conductivity and optical properties of the material, and realizing the function of an amplitude modulator that can be realized by adjusting the voltage.

[0007] In order to maximize the working bandwidth and performance of the modulator, the present invention uses the formula based on electromagnetic theory (D is the length of the layered metamaterial in the direction parallel to the surface, λ is the wavelength of the working electromagnetic wave, μ r is the relative magnetic permeability, ε r is the relative dielectric constant, k is the control factor) and it is determined that the length of the layered metamaterial in the parallel plane direction is 0.07k times the wavelength of the working electromagnetic wave (k is an arbitrary positive integer). When k is an even number, the modulator behaves as an anti-reflection film structure to achieve the transmission control function. When k is an odd number, the modulator transforms into an anti-reflection film structure to achieve the reflection control function. In addition, we can calculate the amplitude modulation index M = |t 4V -t 0V | / t 0V (where t 4V is the transmittance of the metamaterial when the bias voltage is 4 V, t 0V The performance of the modulator is evaluated by the transmittance of the metamaterial at a bias voltage of 4 V.

[0008] Preferably, when k is 2-6, that is, the length of the layered metamaterial in the direction parallel to the plane is 0.14-0.42 times the wavelength of the working electromagnetic wave, the modulator performance is optimal.

[0009] Furthermore, the semiconductor materials in the layered metamaterials have stable optical properties.

[0010] Preferably, the layered intrinsic semiconductor material is an intrinsic gallium arsenide semiconductor, and the layered doped semiconductor material is an n-type doped gallium arsenide semiconductor.

[0011] Preferably, the thickness of the n-type doped gallium arsenide semiconductor in the vertical plane direction should be less than one tenth of the operating wavelength.

[0012] Furthermore, the material of the dielectric layer has a stable dielectric constant and loss tangent, while ensuring good electrical insulation.

[0013] Preferably, the dielectric layer material is an intrinsic gallium arsenide semiconductor.

[0014] Furthermore, one side of the metal plate is grounded, and the other side is connected to a forward or reverse DC voltage.

[0015] Preferably, the voltage applied to the metal plate is a reverse DC voltage of -4-0V.

[0016] The working electromagnetic wave of the electrically controlled amplitude modulator based on layered metamaterial has an operating wavelength in the visible light band;

[0017] Preferably, the working electromagnetic wave has a working wavelength of 420nm-600nm.

[0018] Furthermore, there are two directions parallel to the layer direction that are perpendicular to each other, namely parallel to the layer direction 1 (x direction) and parallel to the layer direction 2 (y direction).

[0019] The layered metamaterial is prepared by first epitaxially growing a first layer of intrinsic semiconductor on a substrate using an atomic layer deposition method, and then growing a second layer of doped semiconductor on the first layer; and so on, to complete the growth of a periodic unit.

[0020] Specifically, more than 25 deposition cycles are required to grow each layer of material, then mill the layer and grow the next layer on the milled surface.

[0021] Specifically, after one periodic unit is grown using molecular beam growth, a second periodic unit is grown thereon; and so on, until the entire layered growth is completed.

[0022] Specifically, after preparing a periodic unit by epitaxial growth, the method further includes: a step of milling the last layer.

[0023] Specifically, an atomic layer deposition method is used to epitaxially grow a dielectric layer on the outermost layer of the layered structure.

[0024] Specifically, after all layers are grown, the substrate is peeled off using acetone, and the surface of the layered structure after the substrate is peeled off is milled using a focused ion beam.

[0025] Specifically, a metal layer is deposited on the dielectric layer using an evaporation coating technique, and a photolithography and lift-off process are used to form a desired electrode pattern.

[0026] The present invention has the following beneficial effects: (1) The present invention adopts a layered structure in which n-type or p-type doped semiconductors and intrinsic semiconductors are grown alternately, and the layered structure is connected to dielectric layers in parallel to the plane direction, and the dielectric layers are connected to metal plates. By connecting a forward or reverse DC voltage to the metal plate, the magnitude of the voltage can be changed to continuously adjust the optical properties of the device. (2) The present invention introduces an innovative metamaterial optical amplitude modulator design method, which can only adjust the amplitude of the transmitted or reflected electromagnetic wave without affecting the respective phases. This dynamic and efficient control technology has broad application prospects in the field of optical communications. (3) The present invention has a high processing error tolerance, and the device performance can be optimized by adjusting the doping concentration of the doped semiconductor and the thickness of the layered structure in the vertical plane direction. (4) In the preparation method provided by the present invention, more than 25 deposition cycles are required when preparing each layer of material, and after all periodic layers are grown, the substrate is peeled off with acetone, which is conducive to achieving the uniformity of the structure of each layer of material, reducing milling errors, and thus improving the stability and yield of components while improving the transmission performance of the device. (5) The present invention has a simple structure, low processing difficulty, and has many advantages such as high efficiency and easy integration. The present invention has a broad application prospect in the field of optical control components. BRIEF DESCRIPTION OF THE DRAWINGS In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. 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 paying creative work.

[0027] Figure 1 A schematic structural diagram of an electrically controlled amplitude modulator based on layered metamaterials provided in an embodiment of the present invention.

[0028] Figure 2 The carrier concentration and distribution diagram of a unit of a layered metamaterial when a voltage is applied provided by an embodiment of the present invention.

[0029] Figure 3 The embodiment of the present invention provides the transmittance of the incident light when it is incident on the modulator along a parallel plane.

[0030] Figure 4 The embodiment of the present invention provides a curve of the amplitude tuning index of the transmitted electromagnetic wave when the incident light is incident on the modulator along a parallel plane.

[0031] Figure 5 The embodiment of the present invention provides a transmission phase diagram when the incident light is incident on the modulator along a parallel plane.

[0032] In the figure, 1 is the intrinsic semiconductor layer, 2 is the doped semiconductor layer, 3 is the periodic unit, 4 is the dielectric layer, 5 is the metal electrode, 6 is the electromagnetic wave incident along the parallel plane, and 7 is the electromagnetic wave transmitted along the parallel plane. DETAILED DESCRIPTION

[0033] The technical scheme in the embodiment of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0035] The present invention is an electrically controlled amplitude modulator based on layered metamaterials, comprising a layered metamaterial stacked by a plurality of periodic units, a dielectric layer and a metal plate, wherein a doped semiconductor layer and a half intrinsic semiconductor layer connected on both sides form a periodic unit; the thickness of the layered doped semiconductor in a direction perpendicular to the layer is less than one tenth of the operating wavelength; the thickness of the dielectric layer on both sides of the layered metamaterial is equal and the thickness in a direction perpendicular to the layer is greater than the thickness of the periodic unit. The construction material of the periodic unit can be semiconductors such as gallium arsenide and silicon, preferably gallium arsenide. The doping type of the doped semiconductor layer can be n-type or p-type, preferably n-type. The doping concentration of the doped semiconductor layer is preferably 10 18 -10 19 cm -3 .

[0036] The present invention includes the regulation of reflected light amplitude and transmitted light amplitude. The positive and negative poles of the external electrical control device are connected to the metal plate, and then the carrier concentration and its distribution inside the layered metamaterial periodic unit are changed by changing the injection current or the loading voltage, thereby changing the conductivity of the metamaterial to achieve regulation of the light field intensity. In addition, by changing the above-mentioned control factor k, the regulation of the reflected light amplitude or the transmitted light amplitude is achieved. Here, when k is an even number, the transmission control function is achieved; when k is an odd number, the reflection control function is achieved. Taking the transmitted light amplitude control function as an example, the specific parameters of the embodiment are as follows:

[0037] The embodiment of the present invention provides a schematic diagram of the structure of an electrically controlled amplitude modulator based on layered metamaterials, such as Figure 1 As shown in Figure 2, the periodic unit of the layered metamaterial is composed of an intrinsic layer and a doped semiconductor layer, with thicknesses of 20 nm and 30 nm respectively. The constituent materials are intrinsic GaAs semiconductor and n-type doped GaAs semiconductor. The doping concentration of n-type doped GaAs semiconductor is 7.5×1018 cm -3 The thickness of the dielectric layer in the vertical direction of the periodic unit is 60nm.

[0038] The working electromagnetic wave is incident perpendicular to the parallel plane 1 (x direction), the polarization direction of the electromagnetic wave is z direction, and the wavelength is 420nm-600nm. The length of the metamaterial optical modulator in the parallel plane direction is 207.6nm, and the thickness of the periodic unit is 50nm. The metal plate is externally connected to a reverse DC voltage of -4-0V.

[0039] When the applied voltage decreases from 0V to -4V, the electron distribution inside the doped semiconductor becomes uneven. Figure 2 As shown, as the reverse bias voltage decreases from 0V to -4V, the width of the layered doped semiconductor in one periodic unit decreases from 30nm to close to 0 in the stable state.

[0040] As the reverse bias voltage increases, the length of the layered metamaterial parallel to the plane is different, and its transmission effect is slightly different. Figure 3 As shown in the figure, when the working electromagnetic wave is incident perpendicular to the parallel plane 1 (x direction) and the length of the layered metamaterial in the parallel plane direction is 0.42 times the working wavelength, the transmission effect is optimal. At this time, the transmittance of the layered metamaterial optical modulator is proportional to the reverse bias voltage and close to 1, realizing the function of an electrically controlled modulator. Figure 4 As shown, k is an even number, and the modulator realizes the amplitude control of the transmitted light. When k = 6, that is, the length in the parallel plane direction is 0.42 times the working wavelength, the amplitude tuning index of the transmitted electromagnetic wave is the largest, and the metamaterial transmission performance is the best at this time. Figure 5 As shown, when the wavelength of the working electromagnetic wave is around 500nm, no matter how the external voltage is adjusted, the phase value of the transmitted light does not change, realizing the function of a pure amplitude modulator.

[0041] In some preferred embodiments, the cut-off voltage of the electrically controlled amplitude modulator based on layered metamaterials is that, according to circuit theory, each periodic unit is connected in series and the voltages obtained are the same, so the cut-off voltage increases exponentially with the increase in the number of periodic unit layers.

[0042] In some preferred embodiments, the dielectric layer between the layered metamaterial and the metal plate can prevent the layered doped semiconductor from directly contacting the metal plate, thereby avoiding the flow of electrons and affecting the control characteristics of the device.

[0043] In some preferred embodiments, the thickness of the dielectric layer in the vertical direction should be greater than the thickness of the unit structure, so as to reduce the disturbance of free carriers inside the periodic unit. This can effectively isolate adjacent periodic units and reduce the electromagnetic coupling between them, so that each periodic unit can interact with the incident electromagnetic wave independently. This not only helps to improve the wave absorption efficiency of the metamaterial, but also enhances its absorption or scattering ability for light of a specific wavelength, achieving a better electromagnetic wave control effect. In addition, the thickness of the dielectric layer in the vertical direction is greater than the thickness of the unit structure, which can also prevent reverse breakdown. Increasing the thickness of the dielectric layer can increase the breakdown voltage, suppress electron tunneling, and effectively reduce the risk of current leakage and breakdown caused by reverse voltage.

[0044] In some preferred embodiments, the dielectric layers on both sides of the layered metamaterial are of equal thickness. This symmetrical design helps maintain the stability of the structure and reduce the disturbance inside the periodic unit. Regardless of whether the applied voltage is forward biased or reverse biased, the carrier concentration and its distribution change in the layered metamaterial are better, which helps improve the performance of the modulator.

[0045] In some preferred embodiments, the thickness of the layered doped semiconductor in the direction perpendicular to the layer is less than one tenth of the working wavelength. Such a design can ensure that when an electromagnetic wave is incident, the distance of the free electrons in the layered doped semiconductor to oscillate within the layer reaches an effective path, so that the oscillation of the electrons can resonate with the incident electromagnetic wave. This resonance effect can significantly enhance the material's ability to absorb or scatter light of a specific wavelength.

[0046] In some preferred examples, simulation results show that the conductivity of the layered metamaterial changes with the change of the external bias voltage, while the relative dielectric constant and magnetic permeability remain almost unchanged. This characteristic does not affect the transmission phase, allowing the modulator to achieve a pure amplitude control function.

[0047] In some preferred embodiments, if the k value is small, the modulation bandwidth of the metamaterial is relatively narrow, resulting in insufficient regulation performance for a specific wavelength. On the contrary, when the k value is too large, the material may be too thick and affect its transmittance, thereby affecting the overall regulation performance of the material.

[0048] Based on the above description, those skilled in the art should have a clear understanding of the electrically controlled amplitude modulation device based on layered metamaterials provided in the embodiments of the present invention.

[0049] The embodiment of the present invention provides a method for preparing a modulator, the method comprising: preparing a first layer of intrinsic semiconductor by epitaxial growth on a substrate using an atomic layer deposition method, then milling the layer, and growing a second layer of n-type doped semiconductor on the milled surface; and so on, completing the growth of one periodic unit. After completing the growth of one periodic unit by molecular beam growth, completing the growth of a second periodic unit on the periodic unit; and so on, until the growth of the entire layered structure is completed. Then, epitaxially preparing a dielectric layer on the outermost side of the layered structure by an atomic deposition method. Finally, a metal layer is deposited on the dielectric layer by evaporation coating technology, and photolithography and lift-off processes are used to form the desired electrode pattern.

[0050] In summary, the electrically controlled amplitude modulator based on layered metamaterials provided by the present invention, by utilizing the electromagnetic wave interference effect, Brugmann effective medium theory, the resonance theory of free electrons, electromagnetic theory and mature layered metamaterial processing technology, effectively integrates and improves the functions and performance of the modulator, while greatly simplifying the design, processing and manufacturing processes of the traditional modulator, thereby obtaining an electrically controlled amplitude modulator based on layered metamaterials with a more compact structure and better performance.

[0051] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0052] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An electrically controlled amplitude modulator based on a layered metamaterial, comprising a layered metamaterial, a dielectric layer and a metal plate, characterized in that: The layered metamaterial is composed of layered intrinsic semiconductors and layered doped semiconductors stacked alternately. The doped semiconductor layer and the half intrinsic semiconductor layer connected on both sides form a periodic unit, and the thickness of the periodic unit in the vertical plane direction is the periodic unit thickness; the outermost layers of the layered metamaterial in the vertical plane direction are respectively connected to dielectric layers of the same thickness, and the thickness of the dielectric layer is greater than the thickness of the periodic unit; the dielectric layers are respectively connected to metal plates. The length of the modulator in the parallel plane direction is 0.14-0.42 times the wavelength of the working electromagnetic wave. The metal plates connected to the outermost layer of the metamaterial are applied with a forward or reverse voltage, and the voltage difference on each periodic unit is less than or equal to 4V. By changing the carrier concentration and its distribution in the doped region by voltage, the conductivity of the metamaterial changes, realizing an optical modulator with constant phase but adjustable amplitude.

2. The layered metamaterial according to claim 1, characterized in that: The layered doped semiconductor may be an n-type semiconductor or a p-type semiconductor, and is preferably an n-type semiconductor.

3. The layered metamaterial according to claim 1, characterized in that: The thickness of the doped semiconductor layers of the layered metamaterial in the vertical direction is less than one tenth of the operating wavelength.

4. The semiconductor according to claim 2, characterized in that The semiconductor is selected to have stable, low-loss optical properties. Preferred semiconductors are gallium arsenide and silicon.

5. The dielectric layer according to claim 1, characterized in that: The dielectric layer is made of a material with a relatively high dielectric constant and matching the adjacent semiconductor lattice to ensure high electrical insulation and good product yield. The dielectric layer material is preferably an intrinsic gallium arsenide semiconductor.

6. The electrically controlled amplitude modulator based on layered metamaterial according to claim 1, characterized in that: The working electromagnetic wave is incident along a direction parallel to the layer and perpendicular to the surface of the layered metamaterial.

7. The working electromagnetic wave according to claim 6, characterized in that: The working electromagnetic wave is visible light, and the preferred wavelength range is 480nm-520nm.

8. Parallel to the layer direction according to claim 6, characterized in that: There are two directions parallel to the slice direction and perpendicular to each other, namely parallel to the slice direction 1 (x direction) and parallel to the slice direction 2 (y direction).

9. According to claim 1, when the length of the modulator in the parallel plane direction is preferably 0.42 times the wavelength of the working electromagnetic wave, the regulation effect is best.

10. The layered metamaterial according to claim 1, characterized in that: include: The first layer of intrinsic semiconductor is prepared by epitaxial growth on the substrate using the atomic layer deposition method, and then a second layer of n-type or p-type doped semiconductor is grown on the layer; and so on, the growth of one periodic unit is completed.

11. The layered metamaterial according to claim 10, characterized in that: include: More than 25 deposition cycles are required to grow each layer of material, then mill it off and grow the next layer on top of the milled surface.

12. The layered metamaterial according to claim 10 and claim 11, characterized in that: After the growth of one periodic unit is completed by molecular beam growth, a second periodic unit is grown on the periodic unit; and so on, until the growth of the entire layered structure is completed.

13. The preparation method according to claim 10, characterized in that: After all periodic layers were grown, the substrate was peeled off with acetone, and the surface of the layered peeled substrate was milled using a focused ion beam.

14. The dielectric layer according to claim 1, characterized in that: A dielectric layer is prepared by epitaxial growth on the outermost layer of the layered metamaterial using atomic layer deposition.

15. The metal plate according to claim 1, characterized in that: The metal layer is deposited on the dielectric layer using evaporation coating technology, and the required electrode pattern is formed using photolithography and lift-off processes.

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