CN109375390B - Electro-optical modulator based on graphene - Google Patents
Electro-optical modulator based on graphene Download PDFInfo
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- CN109375390B CN109375390B CN201811602852.2A CN201811602852A CN109375390B CN 109375390 B CN109375390 B CN 109375390B CN 201811602852 A CN201811602852 A CN 201811602852A CN 109375390 B CN109375390 B CN 109375390B
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/03—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect
- G02F1/0305—Constructional arrangements
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/03—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on ceramics or electro-optical crystals, e.g. exhibiting Pockels effect or Kerr effect
- G02F1/0327—Operation of the cell; Circuit arrangements
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F2203/00—Function characteristic
- G02F2203/12—Function characteristic spatial light modulator
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
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- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
The invention discloses an electro-optical modulator based on graphene, which comprises the following parts: the magnetic resonance plasmon polariton surface comprises a substrate, a magnetic resonance plasmon polariton super surface and a single-layer graphene sheet; the electro-optic modulator can change the transmittance of mid-infrared light transmitted through the electro-optic modulator by changing the Fermi level of a single-layer graphene sheet, and the position of a transmission peak on a spectrum is kept unchanged.
Description
Technical Field
The invention relates to the field of electro-optical modulators, in particular to an electro-optical modulator which is applied to free space, works in a middle infrared band and is based on graphene.
Technical Field
Modulating light is a fundamental stone for realizing various applications such as display, integrated optical circuit, optical information transmission, optical information processing and other optical media, and plays an important role in research in the optical field. The electromagnetic nature of light imparts a number of properties to light for carrying information such as frequency, phase, polarization, spin, and the like. However, the most straightforward and widely used characteristic for carrying information is amplitude, otherwise known as intensity. Conventional optical modulation devices require a working medium such as various liquid crystals, acousto-optic crystals, and the like. These conventional working media are generally bulk materials, which results in the disadvantages of large size and low modulation rate of the conventional working medium-based optical modulation device. In recent years, the discovery of graphene has provided a new idea for the design of light modulators. Graphene is used as a single carbon atom layer, and the carrier mobility can reach 20000 cm at room temperature2V- 1s-1This means that if graphene can be used as the working medium of a light modulation device, its working speed has a potential of up to several hundred GHz. Meanwhile, the energy band of the graphene has a linear structure near the dirac cone, which means that the carrier concentration in the graphene is sensitive enough, and the graphene can be electrically doped in a back gate voltage mode, so that the Fermi level of the graphene is remarkably moved. These characteristics make graphene very suitable as a working medium for electro-optic modulators. The electro-optical modulator based on the graphene has bright prospects of small size, thin thickness, high speed, low power consumption and the like.
Generally, the photoelectric modulator based on graphene adopts a working principle that the fermi level of graphene is changed, so that the dielectric function of graphene is changed, the resonance peak of a system moves on a spectrum according to a material disturbance theory, and finally, the spectrum intensity is relatively changed under the working wavelength. However, this mode of operation with formant shifting has the disadvantage that the photodetector is more or less always responsive over a frequency range, and therefore, if the range of formant frequency shifting is less than the frequency response range of the photodetector, the output signal of the photodetector will not change. This would lose part of the switching ratio potential of the electro-optic modulator. To solve this drawback, the frequency shift range of the electro-optical modulator must be extended, which requires a complex and difficult structural design; or a laser signal light source with excellent monochromaticity is adopted, but an LED signal light source cannot be adopted, which increases the cost of the electro-optical modulator.
Disclosure of Invention
The invention aims to alleviate the inherent defects of the electro-optical modulator based on graphene, and discloses the electro-optical modulator which is designed by adopting a new working principle, can directly modulate the intensity of a resonance peak without causing the movement of the resonance peak, works in a middle infrared band, has good modulation performance and is based on graphene.
The invention provides an electro-optical modulator based on graphene, which is characterized by comprising the following characteristics:
the electro-optical modulator comprises the following three parts: the magnetic resonance plasmon artificial super-surface structure comprises a substrate, a magnetic resonance plasmon artificial super-surface and a layer of single-layer graphene sheet; wherein, the substrate is made of a mid-infrared transparent material; the magnetic resonance plasmon artificial super surface is positioned on the substrate; the single-layer graphene sheet is positioned above the magnetic resonance plasmon artificial super surface and is in direct contact with the magnetic resonance plasmon artificial super surface;
in the electro-optical modulator, the Fermi level of the single-layer graphene sheet can be dynamically modulated through the voltage of a back gate;
in the electro-optical modulator, magnetic resonance exists on the magnetic resonance plasmon artificial super surface, and the resonance frequency is blue-shifted along with the increase of the Fermi energy level of the single-layer graphene sheet;
in the electro-optical modulator, Wood abnormality exists on the artificial super surface of the magnetic resonance plasmon;
in the electro-optical modulator, the refractive index of the substrate is matched with the period of the magnetic resonance plasmon artificial super surface, so that when the Fermi level of the single-layer graphene sheet is changed, the resonance frequency of the magnetic resonance plasmon artificial super surface can be coupled with Wood abnormity;
sixthly, the electro-optic modulator works in a middle infrared band and a free space, the adopted incident light is linearly polarized light, and the polarization direction is parallel to the surface of the substrate and vertical to the extension direction of the metal strip grating;
the working wavelength of the electro-optical modulator is positioned in the abnormal neighborhood of Wood and deviates from 100 to 300 nanometers;
the working mode of the electro-optical modulator is to regulate and control the transmissivity of the mid-infrared light penetrating through the magnetic resonance plasmon artificial super surface; in the working process, the resonance frequency of the transmission peak does not move, and only the transmissivity changes;
ninthly, the working principle of the electro-optical modulator is that the resonance frequency of the magnetic resonance plasmon super surface is controlled by controlling the Fermi level of the single-layer graphene sheet, so that the interaction strength of magnetic resonance and Wood abnormity in the magnetic resonance plasmon super surface is controlled, and finally the transmittance is regulated and controlled under the working wavelength;
the transmissivity of the electro-optical modulator at the wavelength (r) is in an exponential trend along with the Fermi level of a single-layer graphene sheet.
⑪, when the structure parameter changes, the modulation performance of the electro-optic modulator is not affected by more than 10%;
⑫, the insertion loss is 0.7dB to 1.5dB, the on-off ratio is 12 to 20, and the modulation depth is 92% to 95% according to different structural parameter combinations.
The invention provides an electro-optical modulator which is characterized in that the magnetic resonance plasmon artificial super surface has the following characteristics:
the grating structure comprises an upper metal flat plate with a gap, a middle dielectric coupling layer and a lower metal strip grating structure;
secondly, the metal flat plate with the gap on the upper layer and the metal strip grating on the lower layer are coupled into a whole through the middle coupling layer, and plasmon magnetic resonance exists.
The novel photoelectric modulator based on graphene provided by the invention controls the resonance frequency of the magnetic resonance plasmon super surface by controlling the Fermi level of the single-layer graphene sheet according to a new principle, so that the interaction strength of magnetic resonance and Wood abnormity in the magnetic resonance plasmon super surface is controlled, the transmittance is finally regulated and controlled under the working wavelength, and a transmission peak does not move on a spectrum, so that the on-off ratio and the modulation depth are improved; the novel electro-optical modulator based on graphene provided by the invention has the insertion loss as low as 0.7 dB; the novel electro-optical modulator based on the graphene has good structural parameter tolerance.
Drawings
Fig. 1 is a schematic structural diagram of a novel graphene-based electro-optic modulator according to the present invention and a front view of the schematic structural diagram;
FIG. 2 is a graph of the transmission spectrum of the first example as a function of the Fermi level of the graphene;
FIG. 3 is a diagram of a magnetic field distribution corresponding to a transmission peak of the first embodiment when the Fermi level of graphene is 0.1eV, and a dotted line indicates the position of Al;
FIG. 4 is a diagram of a magnetic field distribution corresponding to a transmission peak of the first embodiment when the Fermi level of graphene is 1.0eV, and a dotted line indicates a position of Al;
FIG. 5 is a graph of transmittance at a transmission peak as a function of the Fermi level of graphene according to an example, wherein the solid line is an exponential function fit curve;
FIG. 6 is a graph comparing the transmission spectra of different embodiments as a function of the graphene Fermi level, where "On/Off" represents the On-Off ratio and "MD" represents the modulation depth.
Detailed Description
The following detailed description of implementations of the present invention refers to the accompanying drawings.
Example one
In this embodiment, the proposed novel graphene-based electro-optic modulator is described as follows: wherein the metal material is selected to be aluminum, the substrate material is selected to be silicon, and the coupling layer material is selected to be silicon dioxide; the structural parameters, as shown in fig. 1, are L equal to 1.6 microns, g equal to 40 nanometers, P equal to 1.8 microns, tm equal to 50 nanometers, and td equal to 350 nanometers. In other embodiments, the materials used in the present embodiment are the same unless otherwise specified. In other embodiments, the parameters of the structure are the parameters of the present embodiment unless otherwise specified.
Example two
In this example, L is equal to 1.5 microns.
EXAMPLE III
In this example, L is equal to 1.8 microns.
Example four
In this embodiment, td is equal to 150 nm.
EXAMPLE five
In this embodiment, td is equal to 250 nanometers.
EXAMPLE six
In this embodiment, the centers of the upper and lower layers of the magnetic resonance plasmon super surface generate a dislocation of 100 nm.
EXAMPLE seven
In this embodiment, the centers of the upper and lower layers of the magnetic resonance plasmon super surface generate a dislocation of 200 nm.
Fig. 1 shows a schematic structural diagram of a novel graphene-based electro-optical modulator according to the present invention and a front view thereof, wherein structural parameters are labeled in the front view. Fig. 2 is a transmission spectrum at different graphene fermi levels for the first example, and it can be seen that the transmission decays rapidly to zero at the Wood anomaly. In fig. 2, the dashed line indicates the position of the operating wavelength, and it can be seen that the transmittance gradually increases as the fermi level of the graphene increases, and the position of the operating transmission peak does not move accordingly. In contrast, the non-operational transmission peak to the left of the Wood anomaly in fig. 2 shifts with changes in the fermi level. Fig. 3 is a magnetic field distribution diagram corresponding to a transmission peak when the fermi level of the graphene is 0.1eV according to an embodiment, and it can be seen that the magnetic field in the coupling layer is significantly enhanced, which can infer the occurrence of magnetic resonance. Therefore, the transmission peak on the left side of the Wood anomaly is caused by plasmon magnetic resonance, and the resonance peak is blue-shifted along with the increase of the graphene Fermi level and gradually interacts with the Wood anomaly. Fig. 4 is a magnetic field distribution diagram corresponding to a transmission peak when the fermi level of graphene is 1.0eV according to an example, and it can be seen that the magnetic field distribution is obviously different from that in fig. 3, the magnetic field in the coupling layer is obviously weakened, and the magnetic field in the gap of the upper metal plate is obviously strengthened, reflecting that the plasmon magnetic resonance and Wood anomaly interact. Fig. 5 shows the variation trend of the transmittance at the first transmission peak with the fermi level of the graphene in the example, and it can be seen that the variation of the transmittance shows a significant nonlinear trend, and conforms to the exponential variation law. FIG. 6 is a graph comparing the transmission spectra of different examples as a function of the Fermi level of the graphene. It can be seen that, in different embodiments, the modulation effect of the novel graphene-based electro-optical modulator provided by the invention is basically not affected by parameter changes, and has very good experimental error tolerance.
Finally, it is noted that the disclosed embodiments are intended to aid in further understanding of the invention, but those skilled in the art will appreciate that: various substitutions and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the invention should not be limited to the embodiments disclosed, but the scope of the invention is defined by the appended claims.
Claims (1)
1. An electro-optical modulation method for directly modulating intensity is characterized in that a graphene-based electro-optical modulator is adopted, and the graphene-based electro-optical modulator comprises the following components: firstly, a layer of single-layer graphene sheet, a metal flat plate with gaps, a layer of dielectric coupling layer, a metal strip grating structure and a substrate are formed; the method is further characterized by: the metal flat plate with the gap, the dielectric coupling layer and the metal strip grating structure at the lower layer are coupled into a whole to form a magnetic resonance plasmon artificial super surface; the single-layer graphene sheet is positioned above the magnetic resonance plasmon artificial super surface and is in direct contact with the magnetic resonance plasmon artificial super surface, and the Fermi-carrying energy level and the dielectric constant of the single-layer graphene sheet are regulated and controlled through the voltage of a back gate; the refractive index of the substrate is matched with the period of the magnetic resonance plasmon artificial super surface, so that when the Fermi level of the single-layer graphene sheet is changed, the resonance frequency of the magnetic resonance plasmon artificial super surface is abnormally coupled with Wood; the electro-optical modulator works in a middle infrared wave band and a free space, the adopted incident light is linearly polarized light, and the polarization direction is parallel to the surface of the substrate and vertical to the extension direction of the metal strip grating; the working wavelength of the electro-optical modulator is positioned in the vicinity of the Wood anomaly and deviates from 100 to 300 nanometers; in the working process of the electro-optical modulator, the resonance frequency of a transmission peak does not move, and only the transmissivity changes; the transmissivity of the electro-optic modulator is in an exponential change trend along with the Fermi level of the single-layer graphene sheet.
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| GB201902971D0 (en) | 2019-03-06 | 2019-04-17 | Cambridge Entpr Ltd | Transmitters and receivers |
| CN110133876B (en) * | 2019-06-18 | 2020-10-09 | 南开大学 | Terahertz graphene super-surface lens with adjustable focal length and design method |
| CN110515224B (en) * | 2019-09-04 | 2022-11-08 | 哈尔滨理工大学 | Graphene-metal groove metamaterial terahertz slow-light device with double bands capable of being flexibly and selectively regulated |
| CN111123418B (en) * | 2020-01-19 | 2021-11-26 | 中国人民解放军国防科技大学 | Graphene plasmon cavity-perfect absorber coupling nano resonance device |
| CN111258055B (en) * | 2020-02-12 | 2022-05-20 | 贵州民族大学 | Light-operated photoswitch |
| CN111983827B (en) * | 2020-08-21 | 2022-04-26 | 苏州大学 | Near-infrared broadband optical switch based on graphene absorption enhancement |
| CN112504459A (en) * | 2020-11-18 | 2021-03-16 | 中国科学院上海技术物理研究所 | Anisotropic plasmon resonant cavity graphene polarization detector and design method |
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| CN107908019A (en) * | 2017-11-30 | 2018-04-13 | 青岛大学 | Graphene surface phasmon Waveguide array is periodically from the preparation method of image device |
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