A tunable induced transparency terahertz device

Abstract

The application belongs to the field of metamaterial structure, and particularly relates to a tunable induced transparent terahertz device, which comprises a bias voltage and a silicon substrate layer, a graphene layer and a silicon cover layer arranged in sequence, one electrode of the bias voltage is connected with the graphene layer, and the other electrode is connected with the silicon cover layer, the graphene layer is formed by combination of multiple graphene units, the multiple graphene units are arranged periodically, the graphene unit comprises a first graphene strip and a second graphene strip perpendicular to each other, and two graphene blocks symmetrically arranged on both sides of the second graphene strip, the first graphene strips of graphene units in the same column are collinear and connected, the application can realize very obvious double-plasmon induced transparent phenomenon by eliminating the interference of bright mode and dark mode in the terahertz region, the desired slow light effect can be obtained by adjusting the external voltage, and in addition, the device also has the advantages of small size, thin thickness, easy integration and manufacturing and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of metamaterial structure, and particularly relates to a tunable induced transparent terahertz device. BACKGROUND

[0002] In the implementation of photoelectric devices, basically, the functions of the devices are realized by relying on photoelectric materials to absorb and convert the energy of the incident electromagnetic wave into electric energy or electric signals, and therefore the absorption performance of the photoelectric materials is crucial. When the conversion efficiency of the device is certain and cannot be improved, the more the absorbed electromagnetic wave energy is, the greater the intensity of the generated electric energy or electric signals is, and the efficiency of the entire device will be greatly improved. The absorption rate of a single graphene layer is only 2.3%, which is far from meeting the functional requirements of the device.

[0003] In addition, the slow light effect is an abnormal physical phenomenon existing in high dispersion devices and media. Through the study of the slow light, not only can the understanding of the nature of the interaction between light and matter be deepened, but also new physical phenomena can be discovered. By using the slow light effect, on the one hand, optical delay devices, optical buffers and the like can be constructed, and these devices will be the core devices for solving the problems of optical routing and optical switching in an all-optical communication system. On the other hand, when an optical pulse is transmitted in a slow light waveguide, it will experience spatial compression, and the energy density will be significantly increased, which can effectively improve the sensitivity of a sensor.

[0004] At present, the generation mechanism of the slow light effect can be divided into two categories: based on material dispersion and based on structural dispersion. Due to the limitation of materials, it is difficult to make a great breakthrough based on material dispersion, and the effect of the slow light effect based on the structural dispersion is not ideal due to the difficulty in changing the size and parameters of the structure. SUMMARY

[0005] The technical problem to be solved by the application is to provide a tunable induced transparent terahertz device with good slow light effect.

[0006] The application provides a tunable induced transparent terahertz device, which comprises a bias voltage and a silicon substrate layer, a graphene layer and a silicon cover layer arranged in sequence, one electrode of the bias voltage is connected with the graphene layer, and the other electrode is connected with the silicon cover layer, the graphene layer is formed by combining a plurality of graphene units, the plurality of graphene units are arranged periodically, the graphene unit comprises a first graphene strip and a second graphene strip which are perpendicular to each other, and two graphene blocks which are symmetrically arranged on both sides of the second graphene strip, and the first graphene strips of graphene units in the same column are collinear and connected.

[0007] Further, one end of the second graphene strip is arranged in the middle of the first graphene strip, and one end of the graphene block is arranged in the middle of the second graphene strip.

[0008] Further, the first graphene strip is 4 microns long and 0.5 microns wide; the second graphene strip is 3 microns long and 0.6 microns wide; and the graphene block is 1.5 microns long and 0.7 microns wide.

[0009] Further, the second graphene in the single graphene unit is spaced 4 microns from the first graphene strip at one end of the first graphene strip, and the first graphene strip in an adjacent row of graphene units.

[0010] Further, the silicon substrate layer is 0.25 microns thick.

[0011] Further, the silicon cover layer is 0.15 microns thick.

[0012] The present application has the beneficial effect that in the induced transparent terahertz device provided by the present application, the electric field component in the central axis direction of the first graphene strip in the graphene unit cannot be directly excited by the incident light wave, and the graphene unit is in dark mode in the spectrum, and the curve in the absorption effect diagram of the transparent effect is a curve with a refractive index of almost 1; the second graphene strip and the two symmetric graphene blocks can be directly excited by the incident light, and they are in two bright modes in the spectrum, and they form classic Lorentz curves at 3.02 THz and 4.78 THz, respectively, in the absorption effect diagram of the transparent effect. The mutual interference between the three modes of one dark mode and two bright modes can obtain a very obvious double plasmonic induced transparency phenomenon.

[0013] Because the graphene units are arranged periodically, the structure does not need to change any structural parameters, and only needs to adjust the bias voltage to change the Fermi level, so as to realize the tuning function of the double plasmonic induced transparency phenomenon and obtain a tunable induced transparent terahertz device.

[0014] In addition, the present terahertz device will produce strong dispersion, and by utilizing this phenomenon, the slow light effect can be realized. The slow light effect is related to the group velocity, that is, the greater the group velocity, the better the slow light effect. The present terahertz device will have strong interference at the resonance frequency of the double plasmonic induced transparency phenomenon, and there will be very obvious protrusions near the transmission valley and the absorption peak of the double plasmonic induced transparency phenomenon caused by strong dispersion, so the present terahertz device has very high group velocity, and thus the slow light effect required can be obtained by adjusting the double plasmonic induced transparency phenomenon.

[0015] This invention achieves a very pronounced dual-plasma-induced transparency (PIT) phenomenon by eliminating interference between bright and dark modes in the terahertz region. Compared to other devices, this device does not require changes to its size parameters; the Fermi level can be altered simply by changing the external bias voltage. In the 1THz-6THz frequency band, the slow-light effect of this device intensifies with increasing Fermi level, with a maximum group velocity of approximately 380. The desired slow-light effect can be obtained by adjusting the external voltage. Furthermore, this device also boasts advantages such as small size, thinness, and ease of integration and fabrication. Attached Figure Description

[0016] Appendix Figure 1 This is a schematic diagram of the structure of the present invention;

[0017] Appendix Figure 2 for Figure 1 The diagram on the right;

[0018] Appendix Figure 3 for Figure 1 Top view;

[0019] Appendix Figure 4 This is a top view of a graphene unit in this invention;

[0020] Appendix Figure 5 This is a diagram illustrating the absorption effect of the surface plasmon-induced transparency effect generated by the present invention.

[0021] Appendix Figure 6 This invention provides a dynamically tunable slow light effect at a Fermi level of 0.8 eV in the graphene layer.

[0022] Appendix Figure 7 This invention provides a dynamically tunable slow light effect at a Fermi level of 0.9 eV in the graphene layer.

[0023] Appendix Figure 8 This invention provides a dynamically tunable slow light effect at a Fermi level of 1.0 eV in the graphene layer.

[0024] Appendix Figure 9 This invention demonstrates the dynamically tunable slow light effect at a Fermi level of 1.1 eV in the graphene layer.

[0025] In the figure, 1-silicon substrate; 2-graphene layer; 21-first graphene strip; 22-second graphene strip; 23-graphene block; 3-silicon capping layer; 4-bias voltage; 41-first electrode; 42-second electrode. Detailed Implementation

[0026] Clearly, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort are within the scope of the present application.

[0027] It should be noted that all the directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative position relationship, movement condition, etc. between components in a certain posture (as shown in the drawings), and if the certain posture changes, the directional indications also change accordingly.

[0028] In addition, the descriptions such as "first", "second" and the like in the present application are only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly specified and limited.

[0029] In the present application, unless otherwise explicitly specified and limited, the terms "connection", "fixation" and the like should be understood in a broad sense, for example, "fixation" can be fixed connection, or detachable connection, or integral; can be mechanical connection, or electrical connection, or physical connection, or wireless communication connection; can be directly connected, or indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For a person of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0030] In addition, the technical solutions of each embodiment of the present application can be combined with each other, but it must be based on the fact that a person of ordinary skill in the art can realize it, and when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, and is not within the scope of protection required by the present application.

[0031] As shown in the accompanying Figures 1-4As shown, the application provides a tunable induced transparent terahertz device, which comprises a bias voltage 4 and a silicon substrate layer 1, a graphene layer 2 and a silicon cover layer 3 arranged in sequence, one electrode of the bias voltage 4 is connected with the graphene layer 2, and the other electrode is connected with the silicon cover layer 3, specifically, the second electrode 42 of the bias voltage 4 is connected with the edge of the graphene layer 2, so that it can be connected with the graphene unit, and the first electrode 41 is arranged above the silicon cover layer 3, wherein the graphene layer 2 is arranged at a local position on the upper surface of the silicon substrate layer 1, and the silicon cover layer 3 fully covers the upper surface of the graphene layer 2, the graphene layer 2 is formed by a plurality of graphene units arranged in a periodic manner, and the graphene unit comprises a first graphene strip 21 and a second graphene strip 22 perpendicular to each other, and two graphene blocks 23 symmetrically arranged on both sides of the second graphene strip 22, and the first graphene strips 21 of the graphene units in the same column are collinear and connected.

[0032] In the induced transparent terahertz device provided by the application, the electric field component in the central axis direction of the first graphene strip 21 in the graphene unit cannot be directly excited by the incident light wave, and it is in a dark mode in the spectrum, and its curve in the is a curve with a refractive index of almost 1; the second graphene strip 22 and the two symmetric graphene blocks 23 can be directly excited by the incident light, and they are in two bright modes in the spectrum, and they respectively form a classical Lorentz curve at 3.02 THz and 4.78 THz in the. Figure 5 Figure 5 The mutual interference between one dark mode and two bright modes can obtain a very obvious double plasmonic induced transparent phenomenon.

[0033] Because the graphene units are arranged in a periodic manner, the structure does not need to change any structural parameters, and only needs to adjust the bias voltage 4 to change the Fermi level, so that the tuning function of the double plasmonic induced transparent phenomenon can be realized, and a tunable induced transparent terahertz device is obtained.

[0034] In addition, the terahertz device can produce strong dispersion, and by utilizing this phenomenon, the slow light effect can be realized. The slow light effect is related to the group velocity, that is, the greater the group velocity, the better the slow light effect, and the terahertz device has strong interference at the resonance frequency of the double plasmonic induced transparent phenomenon, and there is a very obvious protrusion near the transmission valley and the absorption peak of the double plasmonic induced transparent phenomenon caused by strong dispersion, so the group velocity is very high, and thus the slow light effect required can be obtained by adjusting the double plasmonic induced transparent phenomenon.

[0035] ​That is, by eliminating the interference between bright and dark modes in the terahertz region, the present invention can achieve a very obvious double plasmon-induced transparency (PIT) phenomenon. Compared with other devices, this device does not need to change the size parameters, and only needs to change the Fermi level by changing the external bias voltage 4. In the frequency band of 1 THz - 6 THz, the slow light effect of this device is enhanced as the Fermi level increases, and the maximum group velocity is about 380, and the desired slow light effect can be obtained by adjusting the external voltage. In addition, this device also has the advantages of small size, thin thickness, easy integration and fabrication, etc.

[0036] Reference Figure 4 , in one embodiment, one end of the second graphene strip 22 is disposed in the middle of the first graphene strip 21, and one end of the graphene block 23 is disposed in the middle of the second graphene strip 22, and each graphene unit has a "soil"-shaped pattern.

[0037] In one embodiment, the first graphene strip 21 has a length h1 = 4 microns and a width a1 = 0.5 microns; the second graphene strip 22 has a length a2 = 3 microns and a width h5 = 0.6 microns; one of the graphene blocks 23 has a length a4 = 1.5 microns and a width h6 = 0.7 microns, and the other graphene block 23 has a length a5 = 1.5 microns and a width h4 = 0.7 microns.

[0038] The distances h2 = h3 = 1.7 microns from the end of the first graphene strip 21 to both sides in the width direction of the second graphene strip 22.

[0039] In addition, one end of the second graphene strip 22 in a single graphene unit, which faces away from the first graphene strip 21, is spaced apart from the first graphene strip 21 in an adjacent row of graphene units by a3 = 0.5 microns, that is, the period of a single graphene unit is 4 microns (that is, longitudinally, the first graphene strip 21 has a length h1 = 4 microns. Horizontally, the width a1 = 0.5 microns of the first graphene strip 21 plus the length a2 = 3 microns of the second graphene strip 22 plus the spacing a3 = 0.5 microns equals 4 microns).

[0040] In one embodiment, the thickness of the silicon substrate layer 1 is 0.25 microns.

[0041] In one embodiment, the thickness of the silicon covering layer 3 is 0.15 microns. <{

[0042] In addition, in one embodiment, the silicon substrate layer 1 and the silicon covering layer 3 have the same external dimensions and only different thicknesses, which can prevent the graphene layer 2 from being oxidized.

[0043] Reference Figures 1-9 , experiments are conducted on the tunable induced transparency terahertz device defined by the above dimensions, and the following effects are obtained:

[0044] After the graphene layer 2 is excited, different resonance frequency plasma waves are generated, and obvious double plasmonic induced transparency phenomenon appears. Figures 3-5 , Figure 4 is a graphene unit, including a first graphene strip 21, a second graphene strip 22 and two graphene blocks 23, Figure 4 is a part of the graphene layer 2, which is formed by a plurality of graphene unit arrays.

[0045] Because the electric field component in the central axis direction of the first graphene strip 21 cannot be directly excited by the incident light wave, it represents a dark mode of the spectrum, and from Figure 5 , it can be seen that its curve is a curve with a refractive index of almost 1; the second graphene strip 22 and the two symmetrical graphene blocks 23 can be directly excited by the incident light, representing two bright modes, and from Figure 5 , it can be seen that classical Lorentz curves are formed at 3.02 THz and 4.78 THz, respectively. The mutual interference between one dark mode and two bright modes can obtain very obvious double plasmonic induced transparency, that is, as shown by the black solid line in Figure 5 .

[0046] Because the graphene units are arranged periodically, the device does not need to change any structural parameters, and only needs to change the Fermi energy level by adjusting the external bias voltage 4 connected thereto, so as to realize the tuning function of the double plasmonic induced transparency phenomenon.

[0047] Because of the strong interference of the surface plasmon of the graphene layer 2 near the transparent peak, strong dispersion will be generated, and by utilizing this phenomenon, the slow light effect can be realized. The slow light effect is related to the group velocity, and the greater the group velocity, the better the slow light effect.

[0048] As shown in Figures 6-9 , Figures 6-9 , the group velocity and the phase shift with the frequency change under different Fermi energy levels from 0.8 eV to 1.1 eV, respectively. It can be observed that as the Fermi energy level continuously rises, the group velocity reaches 380 at 1.1 eV, which is also very excellent in the slow light device. It can be found by observation that because there is strong interference at the resonance frequency of the double plasmonic induced transparency phenomenon, there will be very obvious protrusions near the transmission valley and the absorption peak caused by strong dispersion, which has a very high group velocity, that is, the required slow light effect can be obtained by regulating the double plasmonic induced transparency phenomenon.

[0049] The contents not described in detail in the specification belong to the prior art known to those skilled in the art.

Claims

1. A tunable, induced transparent terahertz device, characterized by, The graphene device comprises a bias voltage (4) and a silicon substrate layer (1), a graphene layer (2) and a silicon cover layer (3) arranged in sequence, one electrode of the bias voltage (4) is connected with the graphene layer (2), and the other electrode is connected with the silicon cover layer (3), the graphene layer (2) is formed by a plurality of graphene units arranged periodically, the graphene units comprise a first graphene strip (21) and a second graphene strip (22) perpendicular to each other, and two graphene blocks (23) symmetrically arranged on both sides of the second graphene strip (22), the first graphene strips (21) of the graphene units in the same column are collinear and connected; The electric field component in the central axis direction of the first graphene strip (21) in the graphene unit cannot be directly excited by the incident light wave, and the graphene unit presents a dark mode in the spectrum; The second graphene strip (22) and the two symmetric graphene blocks (23) are directly excited by the incident light, and present two bright modes in the spectrum; The double plasmonic induced transparency phenomenon is obtained by the mutual interference between one dark mode and two bright modes; The graphene units are arranged periodically, the Fermi level is adjusted by adjusting the bias voltage (4), and the double plasmonic induced transparency phenomenon is tuned.

2. The tunable, transparent terahertz device of claim 1, wherein the first and second electrodes are configured to apply a voltage to the first and second plasmonic layers to tune the terahertz frequency of the device. One end of the second graphene strip (22) is arranged in the middle of the first graphene strip (21), and one end of the graphene block (23) is arranged in the middle of the second graphene strip (22).

3. The tunable, transparent terahertz device of claim 2, wherein the first and second electrodes are configured to apply a voltage to the first and second plasmonic layers to tune the frequency of the induced transparency. The first graphene strip (21) is 4 microns long and 0.5 microns wide, the second graphene strip (22) is 3 microns long and 0.6 microns wide, and the graphene block (23) is 1.5 microns long and 0.7 microns wide.

4. The tunable, transparent terahertz device of claim 3, wherein the first and second electrodes are configured to apply a voltage to the first and second plasmonic layers to tune the frequency of the induced transparency. The end of the second graphene strip (22) in the single graphene unit, which is away from the first graphene strip (21), is spaced apart from the first graphene strip (21) in the adjacent row of graphene units by 4 microns.

5. The tunable, transparent terahertz device of any of claims 1-4, wherein the first and second electrodes are configured to be electrically connected to a voltage source. The thickness of the silicon substrate layer (1) is 0.25 microns.

6. The tunable, transparent terahertz device of any of claims 1-4, wherein the first and second electrodes are configured to be electrically connected to a voltage source. The thickness of the silicon cover layer (3) is 0.15 microns.

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