Optical numerical comparator based on y-type graphene nanoribbons

Abstract

This invention discloses an optical numerical comparator based on Y-type graphene nanoribbons, belonging to the field of silicon-based photonic integrated chip technology. It includes: a Y-type graphene nanoribbon Y1, and Y-type graphene nanoribbons Y2 and Y3 cascaded with Y1. The Y-type graphene nanoribbons Y2 and Y3 are symmetrically designed with respect to Y1. The optical numerical comparator designed in this invention exhibits a minimum extinction ratio of 31.12 dB and an amplitude modulation of 0.77 dB under TM mode light at 9.55 μm. The comparator is located at 0.4 μm. 2 Above the rectangular dielectric layer, mainly composed of graphene nanoribbons in a Y-shaped structure, the graphene nanoribbons are switched on and off by applying a bias voltage to change the chemical potential of graphene, thus realizing the function of a one-bit optical numerical comparator.

Description

Technical Field

[0001] This invention relates to the field of silicon-based photonic integrated chip technology, and in particular to an optical numerical comparator based on Y-type graphene nanoribbons. Background Technology

[0002] Currently, research on Internet technologies such as artificial neural networks and big data, which rely on traditional integrated circuit chips for transmission and computation, has made great progress. However, it faces technical bottlenecks such as reducing energy consumption and improving computing speed and efficiency. Therefore, it is seeking integrated chips based on silicon-based photonic devices to solve the current predicament. The small size and strong localization of graphene surface plasmons provide a possibility for silicon-based photonic integrated chips. Therefore, if a one-bit optical numerical comparator based on graphene surface plasmons can be designed, it will provide new technical support for silicon-based photonic integrated chips. Summary of the Invention

[0003] To address the problems existing in the background art, the purpose of this invention is to provide an optical numerical comparator based on graphene nanoribbons. By applying a bias voltage to change the chemical potential of graphene, the on / off effect of the graphene nanoribbons is achieved, ultimately realizing the function of a one-bit optical numerical comparator.

[0004] To achieve the above technical objectives, the present invention provides an optical numerical comparator based on Y-type graphene nanoribbons, comprising:

[0005] The first Y-type graphene nanoribbon has the same width at its output end W3 as at its input end W1.

[0006] Two second Y-type graphene nanoribbons are connected to the output end W3. The width of the output end W2 of the second Y-type graphene nanoribbon is 1 / 2 the width of the output end W3.

[0007] The optical numerical comparator has a minimum extinction ratio of 31.12 dB and an amplitude modulation of 0.77 dB under TM mode light at 9.55 μm.

[0008] Preferably, the optical numerical comparator is located in an area of ​​0.4 μm. 2 On a rectangular dielectric layer.

[0009] Preferably, the first Y-type graphene nanoribbon includes a nanoribbon edge L0 perpendicular to the output end W1;

[0010] The second Y-type graphene nanoribbon includes a nanoribbon edge L2 perpendicular to the output end W3;

[0011] The length of the nanoribbon edge L0 is half that of the length of the nanoribbon edge L2.

[0012] Preferably, the second Y-type graphene nanoribbon includes a nanoribbon edge L4 perpendicular to the output end W2;

[0013] The Y-shaped opening of the first Y-type graphene nanoribbon has a midline symmetric structure;

[0014] The Y-shaped opening of the second Y-type graphene nanoribbon is a midline asymmetric structure, and the Y-shaped structures of the two second Y-type graphene nanoribbons are symmetric about the X-axis.

[0015] The first Y-shaped graphene nanoribbon has an angle θ1 between its Y-shaped opening and the midline;

[0016] The Y-shaped opening of the second Y-type graphene nanoribbon has angles θ2 and θ3 between it and the midline;

[0017] The included angle θ1 is the same as the included angle θ2, but is not equal to the included angle θ3.

[0018] The length of the nanoribbon edge L4 is positively correlated with the angle θ3.

[0019] Preferably, the nanoribbon edge L0 and nanoribbon edge L2 include a Y-shaped inclined side L1;

[0020] The area between nanoribbon edge L2 and nanoribbon edge L4 includes a Y-shaped hypotenuse L3;

[0021] The length of the hypotenuse L1 of the Y-shape is 1.76 times the length of the hypotenuse L3 of the Y-shape.

[0022] Preferably, the rectangular dielectric layer comprises a substrate, a contact layer, and a dielectric layer arranged sequentially, wherein the substrate has a thickness of 100 nm and a refractive index of 2, the contact layer is a 30 nm thick metal layer Au, and the dielectric layer has a thickness of 20 nm and a refractive index of 1.4.

[0023] The contact layer is used to apply a bias voltage;

[0024] Metal electrodes are added inside the Au metal layer to serve as binary logic control levels and their complements.

[0025] Preferably, the width of the input terminal W1 is 0.04 μm;

[0026] The width of the output terminal W2 is 0.02μm.

[0027] Preferably, the length of the nanoribbon edge L0 is 0.1 μm;

[0028] The length of the nanoribbon edge L1 is 0.3 μm;

[0029] The length of the nanoribbon edge L2 is 0.2 μm;

[0030] The length of the nanoribbon edge L3 is 0.17 μm.

[0031] Preferably, the two second Y-type graphene nanoribbons are cascaded with the first Y-type graphene nanoribbon;

[0032] The structure composed of two cascaded second Y-type graphene nanoribbons includes three output channels, wherein the width of each output channel is the same as the width of the output terminal W2, and the output signal is controlled by setting binary logic level to output in different output channels;

[0033] The nanoribbon edge L6 perpendicular to the second output channel shared by the two second Y-type graphene nanoribbons is positively correlated with the angle θ3.

[0034] The angle between the hypotenuse L5 of the Y-shape and the included angle θ3 is negatively correlated.

[0035] The present invention discloses the following technical effects:

[0036] The optical numerical comparator proposed in this invention has the advantages of high extinction ratio, small size, low loss and high stability, which is beneficial to the development of integrated photonic devices and has certain significance for the high integration development of silicon-based photonic integrated chips. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a description of the XY plane electric field diagram under logic levels 0 and 1 as described in this invention;

[0039] Figure 2 This is a schematic diagram of the optical numerical comparator according to the present invention, wherein (a) is a three-dimensional structural schematic diagram of the optical numerical comparator; and (b) is a top view of the metal electrode layer.

[0040] Figure 3 The electric field distribution diagram of the XY plane and the normalized transmittance curve of each output terminal are shown for each combination case described in this invention.

[0041] Figure 4 This is a top view of the optical numerical comparator described in this invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0043] like Figure 1-4 As shown, this invention provides a design process for a one-bit optical numerical comparator based on graphene surface plasmon resonances, as detailed below:

[0044] 1. Optical switching principle based on plasmon resonances on graphene surface:

[0045] Surface plasmon polaritons (SPPs) are surface waves formed by the collective oscillation of electrons at the interface between a dielectric and a metal, propagating along the interface. These surface waves have wavelengths shorter than the wavelength of light in a vacuum, and propagation constants greater than those of light in a vacuum. Furthermore, SPP waves possess extremely strong optical field confinement capabilities, effectively limiting light propagation to the interface between the dielectric and the waveguide and enabling the transmission of optical power within subwavelength waveguides. Therefore, graphene-based SPPs offer a novel approach for realizing nanoscale photonic integrated devices.

[0046] When the wavelength is within the terahertz and far-infrared wavelength range, in-band conductivity dominates, while interband conductivity is almost negligible. Furthermore, studies on the interaction between graphene and light reveal that when the imaginary part of the complex conductivity of graphene's surface is greater than 0, graphene behaves like a very thin metal film, supporting TM-mode SPPs; conversely, when the imaginary part of the complex conductivity of graphene's surface is less than 0, graphene behaves like a dielectric, supporting TE-mode SPPs. Based on these results and principles, SPPs excited by a TM-mode light source within the far-infrared wavelength range are selected. Additionally, to obtain good SPP transmission phenomena, the effective refractive index n of the light source... eff It is an indispensable factor; the wavelength λ of stimulated SPPs SPP and propagation length L SPP With effective refractive index n eff The relationships can be represented as follows:

[0047]

[0048]

[0049] Based on the above principles, simulation using FDTD software is performed. Figure 1 The results show that SPPs excited by a TM mode light source with a wavelength of 9.55 μm have the following values ​​at μm. c Electric field distribution in the XY plane at μ = 0.1 eV and 1 eV. At this point, in μ... c At 0.1 eV, the effective refractive index n eff =177.822+144.5195i, then the wavelength λ of the stimulated SPPs is... SPP and propagation length L SPP The wavelengths are 53.7 nm and 10.52 nm, respectively; in μ c At 1 eV, the effective refractive index n eff =31.325+0.0335i, then the wavelength λ of the stimulated SPPs is... SPP and propagation length L SPP The wavelengths are 305 nm and 45.37 μm, respectively. Therefore, 0.1 eV is defined as a high-level logic "0", corresponding to the "OFF" state of the graphene nanoribbon; and 1 eV is defined as a high-level logic "1", corresponding to the "ON" state of the graphene nanoribbon.

[0050] 2. Optical numerical comparator based on Y-type graphene nanoribbons:

[0051] A schematic diagram of the overall structure of the one-bit optical numerical comparator proposed in this invention is shown below. Figure 2 As shown in (a), it mainly consists of three Y-type graphene nanoribbons. A 30 nm thick metal layer, Au, is deposited on a 100 nm thick substrate; this layer serves as the contact layer for applying the bias voltage. A 20 nm thick dielectric layer with a refractive index of 1.4 is then added on top of the Au layer. Finally, the Y-type graphene nanoribbons are deposited on top of the dielectric layer. To achieve... Figure 2 To control (a), the present invention adds metal electrodes inside the metal layer Au as binary logic control levels and their complements, as shown in the top view. Figure 2 As shown in (b). Where A and B represent the binary logic levels to be compared, and A and B... B and Both are a pair of complementary control level signals.

[0052] Figure 2 (b) also shows that the area of ​​the overall structure is 0.4 μm. 2 . Figure 4A top view and some dimensional parameters of the proposed one-bit optical numerical comparator are given. θ1, θ2, and θ3 are the angle divisions of the Y1 and Y2 type branch structures, respectively. The Y1 type structure is completely symmetrical vertically, while the Y2 and Y3 type branch structures are identical and symmetrical about the X-axis. When the proposed optical numerical comparator is in operation, a continuous light wave is always input to the Input port, realizing the excitation of SPPs. Then, by changing the logic levels of A and B, the corresponding... and This also changes the transmission path of light in the graphene nanoribbons, thus allowing light waves to be output from different ports.

[0053] 3. Simulation Results and Analysis:

[0054] This invention simulates a one-bit optical numerical comparator with four different input combinations using a 9.55μm TM mode light source in FDTD software. By setting the relevant monitors, this invention obtains the electric field distribution diagram of the XY plane and the normalized transmittance curves of each output terminal for each combination, as shown below. Figure 3 As shown.

[0055] according to Figure 3 The function of the switch: Assuming A = 0, i.e., logic "off", the nanoband L2 channel is closed; assuming A = 1, i.e., logic "on", the nanoband L2 channel is unobstructed; for the control combination of "AB = 00" or "AB = 11", at this time... and Both are either "0" or "1". Light will be transmitted along the graphene nanoribbons in the "ON" state, and finally from C... A＝B (C represents the comparator) The output port has a normalized transmittance of over 0.55; similarly, for the control combination of "AB=01" or "AB=10", the light still propagates along the graphene nanoribbon in the "ON" state, and finally exits from port C. A<B Or C A>B The port output has a normalized transmittance of over 0.65.

[0056] Table 1 presents the normalized transmittance (i.e., normalized power transmittance) values ​​of each output port of the proposed one-bit optical numerical comparator under different input combinations. The comparator's output port C... A＞B C A＝B and C A＜B The minimum extinction ratios were 33.41 dB, 31.12 dB, and 33.49 dB, respectively, and the amplitude modulation of the proposed structure reached 0.77 dB.

[0057] Table 1

[0058]

[0059] In summary, this invention proposes a one-bit optical numerical comparator based on Y-shaped graphene nanoribbons, utilizing the principle of surface plasmon resonance transport. To reduce the transmission loss of the plasmon waveguide, the comparator mainly consists of three Y-shaped graphene nanoribbons with an area of ​​only 0.4 μm. 2 By applying a bias voltage to alter the chemical potential of graphene, the on / off effect of graphene nanoribbons was achieved, ultimately realizing the function of a one-bit optical numerical comparator. Simulation analysis using FDTD software shows that the proposed optical numerical comparator achieves a minimum extinction ratio of 31.12 dB and amplitude modulation of 0.77 dB under 9.55 μm TM mode light. Compared with existing optical numerical comparators, the proposed optical numerical comparator has advantages such as high extinction ratio, small size, low loss, and high stability, which is beneficial to the development of integrated photonic devices and has certain significance for the high integration development of silicon-based photonic integrated chips.

[0060] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0061] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0062] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An optical numerical comparator based on Y-type graphene nanoribbons, characterized in that, include: The first Y-type graphene nanoribbon has the same width at its output end W3 as at its input end W1. Two second Y-type graphene nanoribbons are respectively connected to the two output terminals W3 to form a cascaded structure. The structure composed of the two second Y-type graphene nanoribbons includes three output channels. The width of the output terminal W2 of the second Y-type graphene nanoribbon is 1 / 2 of the width of the output terminal W3. The width of each output channel is the same as the width of the output terminal W2. The Y-shaped opening of the first Y-type graphene nanoribbon has a midline symmetric structure; The Y-shaped opening of the second Y-type graphene nanoribbon is a midline asymmetric structure, and the Y-shaped structures of the two second Y-type graphene nanoribbons are symmetric about the X-axis; The Y-shaped opening of the first Y-shaped graphene nanoribbon has an angle θ1 with the midline; The Y-shaped opening of the second Y-type graphene nanoribbon has angles θ2 and θ3 between it and the midline; The included angle θ1 is the same as the included angle θ2 and is not equal to the included angle θ3; The two branches of the first Y-shaped graphene nanoribbon receive binary logic level signals and their complementary signals respectively, so as to control the graphene nanoribbons on the corresponding branches to be in a conducting or blocking state. Each of the two branches in the second Y-type graphene nanoribbon receives a binary logic level signal and its complementary signal, respectively, to control the graphene nanoribbon on the corresponding branch to be in a conducting or blocking state. The optical numerical comparator has a minimum extinction ratio of 31.12 dB and an amplitude modulation of 0.77 dB under TM mode light at 9.55 μm.

2. The optical numerical comparator based on Y-type graphene nanoribbons according to claim 1, characterized in that: The optical numerical comparator is disposed on a rectangular dielectric layer with an area of ​​0.4 μm2.

3. The optical numerical comparator based on Y-type graphene nanoribbons according to claim 2, characterized in that: The first Y-shaped graphene nanoribbon includes a nanoribbon edge L0 perpendicular to the output end W1; The second Y-type graphene nanoribbon includes a nanoribbon edge L2 perpendicular to the output end W3; The length of the nanoribbon edge L0 is half the length of the nanoribbon edge L2.

4. The optical numerical comparator based on Y-type graphene nanoribbons according to claim 3, characterized in that: The second Y-type graphene nanoribbon includes a nanoribbon edge L4 perpendicular to the output end W2; The length of the nanoribbon edge L4 is positively correlated with the angle θ3.

5. The optical numerical comparator based on Y-type graphene nanoribbons according to claim 4, characterized in that: The nanoband edge L0 and the nanoband edge L2 are separated by a Y-shaped inclined edge L1; The nanoribbon edge L2 and the nanoribbon edge L4 are separated by a Y-shaped inclined edge L3; The length of the hypotenuse L1 of the Y-shape is 1.76 times the length of the hypotenuse L3 of the Y-shape.

6. The optical numerical comparator based on Y-type graphene nanoribbons according to claim 5, characterized in that: The rectangular dielectric layer comprises: a substrate, a contact layer, and a dielectric layer arranged sequentially, wherein the substrate has a thickness of 100 nm and a refractive index of 2, the contact layer is a 30 nm thick metal layer Au, and the dielectric layer has a thickness of 20 nm and a refractive index of 1.

4. The contact layer is used to apply a bias voltage; Metal electrodes are added inside the Au metal layer to receive binary logic control levels and their complements.

7. The optical numerical comparator based on Y-type graphene nanoribbons according to claim 6, characterized in that: The width of the input terminal W1 is 0.04 μm; The width of the output terminal W2 is 0.02μm.

8. The optical numerical comparator based on Y-type graphene nanoribbons according to claim 7, characterized in that: The length of the nanoribbon edge L0 is 0.1 μm; The length of the hypotenuse L1 is 0.3 μm; The length of the nanoribbon edge L2 is 0.2 μm; The length of the hypotenuse L3 is 0.17 μm.

9. The optical numerical comparator based on Y-type graphene nanoribbons according to claim 8, characterized in that: Two second Y-type graphene nanoribbons are cascaded with the first Y-type graphene nanoribbon; The length of the nanoribbon edge L6 perpendicular to the second output channel shared by the two second Y-type graphene nanoribbons is positively correlated with the angle θ3. The length of the Y-shaped hypotenuse L5 between the nanoribbon edge L2 and the nanoribbon edge L6 is negatively correlated with the angle θ3.

Images