An electrically controlled plasmonic switch device based on positive-negative phase velocity waveguide hybrid coupling and a preparation method thereof

Abstract

The application discloses an electrically controlled plasmonic switch device based on positive and negative phase velocity waveguide hybrid coupling and a preparation method, relates to the technical field of optical switch devices, and comprises an antenna, a forward phase velocity waveguide, a reverse phase velocity waveguide, a substrate, a signal detection device and a gate voltage structure. The antenna, the forward phase velocity waveguide and the signal detection device are all connected with the reverse phase velocity waveguide, the reverse phase velocity waveguide is connected with the substrate, and the gate voltage structure is connected with the substrate and the forward phase velocity waveguide respectively. The application utilizes plasmonic hybrid coupling with opposite phase velocities to induce spontaneous symmetry breaking of the system and generate a plasmonic band gap. By adjusting the size of the electric gate voltage, the position of the band gap is controlled, and the transition of plasmons from the on state to the off state is dynamically realized. The method can realize electrically controlled plasmonic switch control in the nanoscale plane, has a large switch ratio and a small modulation voltage, the device structure is simple and easy to implement, has a wide application range and low cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical switching devices, and more particularly to an electrically controlled plasmonic switching device based on hybrid coupling of positive and negative phase velocity waveguides and a preparation method thereof. BACKGROUND

[0002] In photonics and optoelectronics, the basic properties of light such as amplitude, phase, and polarization can be used to achieve effective control of the optical path. Optical switching devices are the most basic type of optical control devices and have wide applications in photonic circuits, analog optics, logic operations, and optical sensors. Traditional optical switching devices include electrical absorption and phase interference schemes. These schemes use electronic transitions and optical phase interference to control the amplitude of light in the waveguide, thereby achieving on-off control of the optical path. However, due to optical diffraction, traditional optical switching devices usually require a size of hundreds of microns to achieve on-off control of the optical path, limiting the integration of optical devices. Therefore, it is necessary to develop efficient, low optical loss, and environmentally stable nanoscale optical switching devices.

[0003] Compared with traditional bulk materials, two-dimensional van der Waals layered materials have atomic layer thickness and can support surface wave transmission of plasmons, breaking through the traditional diffraction limit, greatly reducing the size of the device, and increasing the integration of the device. This makes it unique in optical control and has attracted widespread attention from researchers. Conventional plasmons have positive phase velocity, and their direction is consistent with the direction of energy transmission. For some special plasmons, such as molybdenum oxide phonon plasmons, the in-plane dielectric function is positive, and the out-of-plane is negative. The phase velocity direction of plasmon transmission is opposite to the direction of energy transmission. This unique physical phenomenon brings new dimensions to the control of plasmons. When this plasmon with opposite phase velocity is hybridly coupled to form a waveguide, a symmetry breaking effect occurs spontaneously, resulting in an optical bandgap. By adjusting the electrical gate voltage, the coupling of plasmons can be dynamically controlled, and the off position can be controlled, thereby realizing the continuous change of plasmons from on to off.

[0004] Therefore, how to use the principle of hybrid coupling of positive and negative phase velocity waveguides to obtain a new type of waveguide switching device, realize sub-nanometer scale optical switching control, and reduce the processing and preparation loss is a problem that needs to be solved by those skilled in the art. SUMMARY

[0005] In view of this, the application provides an electrically controlled plasmonic switch device based on positive and negative phase velocity waveguide hybrid coupling and a preparation method.

[0006] An electrically controlled plasmonic switch device based on positive and negative phase velocity waveguide hybrid coupling, comprising: an antenna, a positive phase velocity waveguide, a reverse phase velocity waveguide, a substrate, a signal detection device and a gate voltage structure; the antenna, the positive phase velocity waveguide and the signal detection device are connected with the reverse phase velocity waveguide, the reverse phase velocity waveguide is connected with the substrate, and the gate voltage structure is connected with the substrate and the positive phase velocity waveguide respectively.

[0007] Optionally, the signal detection device is a scattering type scanning near-field optical microscope needle tip for signal detection.

[0008] Optionally, the device further comprises using incident electromagnetic waves to irradiate the antenna to excite plasmons in the waveguide at the boundary.

[0009] Optionally, the incident electromagnetic waves are concentrated in the infrared region, and the wave band is 970-8000 cm -1 .

[0010] Optionally, the plasmons in the waveguide are transmission type plasmons, and specifically can be phonon plasmons, plasmons, and exciton plasmons.

[0011] Optionally, the gate voltage structure is used to change the carrier concentration of the positive phase velocity waveguide, to adjust the hybrid coupling coefficient of the positive and negative phase velocity waveguides, and to control the transmission of the transmission type plasmon waveguide.

[0012] Optionally, a preparation method of an electrically controlled plasmonic switch device based on positive and negative phase velocity waveguide hybrid coupling, comprising: using plasmons with opposite phase velocities to induce spontaneous symmetry breaking of the system, to generate a plasmon band gap, and by adjusting the size of the gate voltage of the gate voltage structure, to adjust the position of the band gap, and to dynamically change the plasmon from an on state to an off state.

[0013] Optionally, the preparation method comprises:

[0014] S1: preparing a waveguide structure with a reverse phase velocity;

[0015] S2: selecting the shape and size of the antenna and manufacturing the antenna;

[0016] S3: selecting a substrate material and preparing the substrate;

[0017] S4: preparing a waveguide structure with positive phase velocity, and transferring the structure to a waveguide structure with reverse phase velocity, to build a gate voltage structure;

[0018] S5: placing an antenna on the switching device, and coupling incident far-field light to the optical switching device to excite a transmission-type plasmonic mode;

[0019] S6: changing the size of the gate voltage to control the continuous change of the device from the on state to the off state.

[0020] Through the above technical solution, compared with the prior art, the application provides an electrically controlled plasmonic switch device based on positive and negative phase velocity waveguide hybrid coupling and a preparation method, which has the following beneficial effects:

[0021] The application provides an electrically controlled plasmonic switch device based on positive and negative phase velocity waveguide hybrid coupling, which comprises an antenna, a positive phase velocity waveguide, a reverse phase velocity waveguide, a substrate, a signal detection device and a gate voltage structure. The antenna, the positive phase velocity waveguide and the signal detection device are connected with the reverse phase velocity waveguide, the reverse phase velocity waveguide is connected with the substrate, and the gate voltage structure is connected with the substrate and the positive phase velocity waveguide respectively. The application realizes the on-off control of the plasmonic waveguide transmission by changing the size of the gate voltage. The application realizes (1) that the plasmonic waveguide breaks through the diffraction limit, compresses the propagation wavelength and realizes the construction of a hundred nanometer scale device; (2) that the on-off control of the plasmonic waveguide can be dynamically realized by changing the size of the gate voltage; (3) that the switching device ensures a smaller control gate voltage < 8V and a larger switching ratio > 25; (4) that the device is constructed by stacking natural materials, so that the loss problem caused by defects introduced in processing is avoided; (5) that the dynamic control plasmonic switch device has a wide range of uses, and the method is simple and easy to implement and low in cost. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description.

[0023] Figure 1 A principle diagram of the electrically controlled plasmonic switch device based on positive and negative phase velocity waveguide hybrid coupling is provided.

[0024] Figure 2 A preparation method flowchart of the electrically controlled plasmonic switch device based on positive and negative phase velocity waveguide hybrid coupling is provided.

[0025] Figure 3A dispersion diagram of the positive and negative phase velocity waveguide overlap region hybrid plasmon provided by the application under different gate voltages.

[0026] Figure 4(a) is a COMSOL simulation cross-sectional view of plasmonic waveguide transmission provided by the application under Fermi energy 0eV-0.3eV.

[0027] Figure 4(b) is an intensity distribution diagram of plasmonic transmittance provided by the application under different Fermi energy.

[0028] Figure 4(c) is a switch ratio of an electrically controlled plasmonic switch device provided by the application under Fermi energy 0eV-0.6eV.

[0029] Figure 5(a) is a structure light field diagram of an electrically controlled plasmonic switch device provided by the application.

[0030] Figure 5(b) is a plasmonic waveguide near-field intensity diagram under the control of an electrical gate voltage provided by the application.

[0031] Figure 6(a) is an experimental extraction intensity diagram of the near-field signal of an electrically controlled plasmonic switch device provided by the application as the Fermi energy changes.

[0032] Figure 6(b) is an experimental distribution diagram of the transmittance and switch ratio of the near-field signal of an electrically controlled plasmonic switch device provided by the application as the Fermi energy changes.

[0033] Among them, 101-antenna, 102-reverse phase velocity waveguide, 103-signal detection device, 104-forward phase velocity waveguide, 105-gate voltage structure, 106-substrate. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0035] The embodiment of the application discloses an electrically controlled plasmonic switch device based on hybrid coupling of positive and negative phase velocity waveguides, comprising: an antenna 101, a forward phase velocity waveguide 104, a reverse phase velocity waveguide 102, a substrate 106, a signal detection device 103 and a gate voltage structure 105; the antenna 101, the forward phase velocity waveguide 104 and the signal detection device 103 are connected with the reverse phase velocity waveguide 102, the reverse phase velocity waveguide 102 is connected with the substrate 106, and the gate voltage structure 105 is connected with the substrate 106 and the forward phase velocity waveguide 104 respectively.

[0036] Further, the signal detection device 103 is a scattering type scanning near-field optical microscope needle point for signal detection.

[0037] Further, the antenna 101 can be a metal antenna, and the size of the metal antenna is variable.

[0038] Further, the antenna 101 is irradiated with an incident electromagnetic wave to excite a plasmon in the waveguide at the boundary.

[0039] Further, the incident electromagnetic wave is concentrated in the infrared region, and the wave band is 970-8000 cm -1 .

[0040] Further, the plasmon in the waveguide is a transmission type plasmon, and specifically can be a phonon plasmon, a plasmon, and an exciton plasmon.

[0041] Further, the gate voltage structure 105 is used to control the transmission of the transmission type plasmon waveguide by changing the carrier concentration of the positive phase velocity waveguide 104, adjusting the hybrid coupling coefficient of the positive and negative phase velocity waveguides, and controlling the transmission of the transmission type plasmon waveguide.

[0042] Further, the preparation method comprises:

[0043] S1: preparing a waveguide structure with a reverse phase velocity;

[0044] S2: selecting the shape and size of the antenna 101, and manufacturing the antenna 101;

[0045] S3: selecting the material of the substrate 106, and preparing the substrate 106;

[0046] S4: preparing the positive phase velocity waveguide 104, and transferring the structure to the reverse phase velocity waveguide 102 to construct the gate voltage structure 105;

[0047] S5: placing the antenna 101 on the switching device, and coupling the incident far-field light to the optical switching device to excite a transmission type plasmon mode;

[0048] S6: changing the size of the gate voltage to control the continuous change of the device from the on state to the off state.

[0049] The present application utilizes the hybrid coupling of plasmons with opposite phase velocities to induce spontaneous symmetry breaking of the system and generate a plasmon band gap. By adjusting the size of the electrical gate voltage, the position of the band gap is adjusted, and the transition of the plasmon from the on state to the off state is dynamically realized. The method can realize the electrically controlled plasmon switching and regulation in the nanoscale plane, has a switching ratio of > 25 and a modulation voltage of less than < 8V. The method is different from the traditional electric absorption modulator and phase modulator, and the device structure is simple and easy to implement, has a wide range of applications, and is low in cost.

[0050] In the specific embodiment, as shown in Figure 3 The embodiment is based on the electrically controlled plasmonic switch device realized by the hybrid coupling of positive and negative phase velocity waveguides. By hybrid coupling of plasmons with opposite phase velocities, the system is induced to spontaneously break symmetry, generating a plasmonic band gap. By adjusting the size of the electrical gate voltage, the position of the band gap is adjusted, and the transition of plasmons from the on-state to the off-state is dynamically realized.

[0051] In the specific embodiment, the cross section of the positive phase velocity waveguide 104 can be square, rod-shaped, ellipsoid and other structures; the geometric size thereof is 100 nm-100 um, and the thickness is 3 nm-600 nm; the material of the positive phase velocity waveguide 104 includes graphene, black phosphorus, silver, iron, copper, aluminum, graphite, and transition metal sulfide.

[0052] In the specific embodiment, the cross section of the positive phase velocity waveguide 102 can be square, rod-shaped, ellipsoid and other structures; the geometric size thereof is 100 nm-100 um, and the thickness is 3 nm-600 nm; the material of the positive phase velocity waveguide 102 includes molybdenum oxide, boron nitride, silicon carbide, gallium oxide, and chromium tungstate.

[0053] In the specific embodiment, the antenna 101 is a metal antenna, and the shape of the metal antenna can be square, rod-shaped, ellipsoid and other structures; the geometric size thereof is 10 nm-20 um, and the thickness is 20 nm-1 um; the material of the antenna 101 is selected from silver, iron, copper, aluminum, platinum, gold and steel.

[0054] In the specific embodiment, the material of the substrate 106 includes inorganic dielectric material and organic polymer material. The inorganic dielectric material is selected from silicon dioxide, silicon, quartz, sapphire, germanium, aluminum oxide, boron nitride, calcium fluoride, magnesium fluoride, gallium arsenide, gallium nitride, gold and silver; the organic polymer material substrate is selected from PET, PMMA, PDMS and plastic.

[0055] In the specific embodiment, a preparation method of an electrically controlled plasmonic switch device based on hybrid coupling of positive and negative phase velocity waveguides includes the following steps:

[0056] Step 1): preparing a waveguide structure with negative phase velocity;

[0057] Step 2): selecting the shape and size of the antenna 101 and making a metal antenna;

[0058] Step 3): selecting the material of the substrate 106 and preparing the substrate 106;

[0059] Step 4): preparing a waveguide structure with positive phase velocity and transferring the structure onto a waveguide structure with negative phase velocity to build a gate voltage structure 105;

[0060] Step 5): transferring a metal antenna on the entire device, and coupling incident far-field light to the optical switch device to excite a transmission-type plasmonic mode;

[0061] Step 6): changing the size of the gate voltage to realize the continuous change of the device from the on state to the off state.

[0062] Further, the method for exciting plasmons is to use incident light to irradiate the antenna 101 to excite plasmons in the waveguide at the boundary.

[0063] In a specific embodiment, a schematic diagram of an electrically controlled plasmonic switch device based on hybrid coupling of waveguides with positive and negative phase velocities is shown in Figure 1 As shown, a transmission-type plasmon is excited by an antenna 101, propagates on a waveguide 102 with negative phase velocity, and a scattered-type scanning near-field optical microscope needle tip is used as a signal detection device 103. The device is placed on a substrate 106, and the coupling coefficient of the plasmon in the waveguide with positive phase velocity 104 is changed by the gate voltage structure 105 to control the transmission of the plasmonic waveguide.

[0064] In a specific embodiment, a flow chart of a preparation method of an electrically controlled plasmonic switch device based on hybrid coupling of waveguides with positive and negative phase velocities is shown in Figure 2 The method comprises the following steps:

[0065] Step 201: preparing a waveguide structure with negative phase velocity.

[0066] The cross section of the waveguide structure with negative phase velocity can be square, rod-shaped, ellipsoidal, and other structures; the geometric size is 100 nm-100 um, and the thickness is 3 nm-600 nm. The material of the waveguide structure with negative phase velocity includes molybdenum oxide, boron nitride, silicon carbide, gallium oxide, and chromium tungstate.

[0067] Step 202: selecting the shape and size of the antenna 101 and making a metal antenna.

[0068] The shape of the metal antenna can be square, grid, and other structures; the geometric size is 10 nm-30 um, and the thickness is 20 nm-5 um. The material of the metal antenna can be selected from iron, aluminum, copper, gold, silver, platinum, and steel.

[0069] Step 203: selecting the material of the substrate 106 and preparing the substrate 106, which is the base layer.

[0070] Step 204: fabricate a waveguide structure with positive phase velocity and transfer the structure onto a waveguide structure with negative phase velocity to construct the gate voltage structure 105;

[0071] The cross section of the waveguide structure with positive phase velocity can be square, rod, ellipsoid, and other structures; the geometric size is 100 nm-100 um, and the thickness is 3 nm-600 nm.

[0072] The material of the waveguide structure with positive phase velocity includes graphene, black phosphorus, silver, iron, copper, aluminum, graphite, and transition metal sulfide.

[0073] Step 205: transfer a metal antenna on the entire device, couple the incident far-field light to the optical switch device, and excite the plasmonic mode.

[0074] The excitation of the plasmonic mode includes: using incident light to irradiate the antenna 101 to excite the plasmon inside the waveguide at the boundary.

[0075] Step 206: change the size of the gate voltage to realize the continuous change of the device from the on state to the off state.

[0076] In specific embodiments, the dispersion diagram of the hybrid plasmon in the overlapping region of the positive and negative phase velocity waveguides under different gate voltages is shown in Figure 3 , which shows that the position of the hybrid plasmon band gap is effectively controlled by the gate voltage. The device supports graphene plasmon with positive phase velocity and molybdenum oxide plasmon with negative phase velocity. In the overlapping region of graphene and molybdenum oxide, the dispersion splitting can be realized to produce a band gap. By adjusting the size of the graphene gate voltage, the position of the band gap can be effectively controlled.

[0077] In specific embodiments, the display diagram of the plasmonic waveguide transmission under different Fermi energy levels is simulated by COMSOL as shown in Figures 4(a)-4(c) , Figure 4(a) shows the COMSOL simulation cross-sectional view of the plasmonic waveguide transmission under the condition that the Fermi energy level is 0eV-0.3eV. Figure 4(b) shows the intensity distribution of the plasmonic transmittance under different Fermi energy levels. Figure 4(c) shows the calculated on-off ratio of the electrically controlled plasmonic switch device under the condition that the Fermi energy is 0eV-0.6eV.

[0078] In specific embodiments, the near-field diagram of the electrically controlled plasmonic switch device based on the hybrid coupling of the positive and negative phase velocity waveguides is shown in Figures 5(a)-5(b) , Figure 5(a) shows the structure light field diagram of the electrically controlled plasmonic switch device. Figure 5(b) shows the plasmonic waveguide near-field intensity diagram under the condition that the gate voltage is adjusted, and the plasmonic near-field signal is gradually turned off as the gate voltage changes from 0V to -8V.

[0079] In a specific implementation, the experimental extracted near-field signal and the experimental data results of transmittance and on-off ratio of the electrically controlled plasmonic switch device are shown in FIGS. 6(a) and 6(b), respectively. Figures 6(a)-6(b) FIG. 6(a) shows the experimental extracted intensity of the near-field signal of the electrically controlled plasmonic switch device as a function of Fermi energy. FIG. 6(b) shows the experimental distribution of the near-field signal transmittance and on-off ratio of the electrically controlled plasmonic switch device as a function of Fermi energy.

[0080] The various embodiments described in this specification are presented by way of example, and each embodiment describes a specific feature of the application that is independently useful. Each embodiment can be used in combination with any other embodiment, and the various embodiments can be combined in any way. The various embodiments are described in detail in this specification, and each embodiment is shown in the appended drawings. The various embodiments are described in the following numbered clauses:

[0081] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and all such modifications that do not depart from the spirit of the application are intended to be within the scope of the application. The scope of the application is to be indicated by the appended claims, rather than the foregoing description, and all changes that come within the meaning of the claims are intended to be embraced therein.

Claims

1. An electrically controlled plasmonic switch device based on positive-negative phase velocity waveguide hybridization coupling, characterized in that, The application relates to a polarization waveguide switch device, which comprises an antenna, a forward phase velocity waveguide, a reverse phase velocity waveguide, a substrate, a signal detection device and a gate voltage structure; the antenna, the forward phase velocity waveguide and the signal detection device are connected with the reverse phase velocity waveguide, the reverse phase velocity waveguide is connected with the substrate, and the gate voltage structure is connected with the substrate and the forward phase velocity waveguide respectively. The device utilizes hybrid coupling of plasmons with opposite phase velocities to induce spontaneous symmetry breaking of the system, generate a plasmonic band gap, and dynamically control the transition of plasmons from an on-state to an off-state by adjusting the size of the electrical gate voltage. The material of the forward phase velocity waveguide comprises graphene, black phosphorus, silver, iron, copper, aluminum, graphite or a transition metal sulfide. The material of the reverse phase velocity waveguide comprises molybdenum oxide, boron nitride, silicon carbide, gallium oxide or chromium tungstate. The material of the antenna comprises silver, iron, copper, aluminum, platinum, gold or steel. The material of the substrate comprises inorganic dielectric material or organic polymer material; the inorganic dielectric material comprises silicon dioxide, silicon, quartz, sapphire, germanium, aluminum oxide, boron nitride, calcium fluoride, magnesium fluoride, gallium arsenide, gallium nitride, gold or silver; and the organic polymer material substrate comprises PET, PMMA or PDMS. The signal detection device is a scattering type scanning near-field optical microscope needle tip used for signal detection. The application also discloses a method for exciting plasmons in the waveguide at the boundary by irradiating the antenna with incident electromagnetic waves.

2. The electrically controlled plasmonic switch device based on positive-negative phase velocity waveguide hybrid coupling according to claim 1, wherein, The plasmons in the waveguide are transmission type plasmons.

3. The electrically controlled plasmonic switch device based on positive-negative phase velocity waveguide hybridization coupling according to claim 2, wherein, The incident electromagnetic waves are concentrated in the infrared region, with a wave band of 970-8000 cm -1 .

4. The electrically controlled plasmonic switch device based on positive-negative phase velocity waveguide hybrid coupling according to claim 2, wherein, The gate voltage structure is used for changing the carrier concentration of the forward phase velocity waveguide, adjusting the hybrid coupling coefficient of the positive and negative phase velocity waveguides, and controlling the transmission of the transmission type plasmon waveguide.

5. The electrically controlled plasmonic switch device based on positive-negative phase velocity waveguide hybridization coupling according to claim 4, wherein, The preparation method comprises the following steps:

6. The preparation method of the electrically controlled plasmonic switch device based on positive-negative phase velocity waveguide hybrid coupling according to claim 1, characterized in that, S1, preparing a waveguide structure with a reverse phase velocity; S2, selecting the shape and size of the antenna and manufacturing the antenna; S3, selecting a substrate material and preparing the substrate; S4, preparing a waveguide structure with a forward phase velocity and transferring the structure to the waveguide structure with the reverse phase velocity to construct a gate voltage structure; S5, placing the antenna on the switch device, coupling incident far-field light to the optical switch device to excite transmission type plasmon modes; S6, changing the size of the gate voltage to control the continuous change of the device from an on-state to an off-state. ​

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