A surface plasmon switch

Abstract

The application discloses a surface plasmon switch, and belongs to the technical field of micro-nano photoelectronic technology.The surface plasmon switch comprises a glass substrate, wherein a gold film is arranged on the glass substrate; the gold film is provided with an asymmetric slit; the slit comprises a small groove and a large groove; PMMA polymers are arranged in the small groove and on the top surface of the gold film; polyimide orientation layers are arranged on both sides in the large groove; a liquid crystal layer is arranged in the remaining part of the large groove; the gold films on both sides of the slit are isolated and insulated; an external voltage is arranged on the gold films on both sides of the slit; the liquid crystal layer is in an electric field formed by the external voltage; incident light is excited to be normally incident from one side of the glass substrate; the refractive index of the liquid crystal layer is changed by switching and adjusting the external voltage; and the switching state of the surface plasmon switch is controlled.The surface plasmon switch provided by the application has the advantages of simple structure, good switching performance, convenience in implementation, rapid response, small size, high practicability and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of micro-nano optoelectronic technology, and particularly relates to a surface plasmon switch. BACKGROUND

[0002] As a surface electromagnetic wave existing at the interface of metal and dielectric, surface plasmon has a propagation direction parallel to the interface of metal and dielectric, and a wavelength shorter than that of free space electromagnetic wave of the same frequency. In the vertical direction of the interface of metal and dielectric, the amplitude of surface plasmon is exponentially attenuated, and the electromagnetic field is tightly limited at the interface of metal and dielectric, showing a sub-wavelength constraint characteristic breaking through the diffraction limit. The above excellent characteristics make surface plasmon have a rich application prospect in the field of optoelectronic integrated devices.

[0003] The present application provides a surface plasmon switch, which provides a new technical path for nanoscale optoelectronic integrated devices and promotes the application development in the field of surface plasmon optoelectronic integrated devices. SUMMARY

[0004] In order to achieve the above-mentioned purpose, the present application provides a surface plasmon switch, which changes the refractive index of a liquid crystal layer by applying an external voltage to realize the switching of the surface plasmon switch state. The present application has the characteristics of simple structure, convenient implementation, good surface plasmon switch characteristics, rapid response, and small integration.

[0005] A surface plasmon switch comprises a glass substrate, the material of the glass substrate is BK7 glass, a gold film is arranged on the glass substrate, the gold film is provided with an asymmetric slot, the slot comprises a small groove and a large groove, the side edge of one side of the small groove is aligned with the side edge of the same side of the large groove, the small groove and the large groove are rectangular grooves, the small groove is located on the side close to the glass substrate, PMMA polymer is arranged in the small groove, polyimide orientation layers are arranged on both sides of the inside of the large groove, a liquid crystal layer is arranged in the remaining part of the inside of the large groove, the PMMA polymer is arranged on the top surface of the gold film, the gold film on both sides of the slot is isolated and disconnected by insulation, an external voltage is arranged on the gold film on both sides of the slot, the liquid crystal layer is in an electric field formed by the external voltage, an excitation incident light is perpendicularly incident into the surface plasmon switch in the direction from the small groove to the large groove, the excitation incident light is linearly polarized light with a wavelength of 700 nm, the polarization direction is perpendicular to the direction of the slot, the refractive index of the glass substrate is 1.52, the refractive index of the PMMA polymer is 1.49, and the refractive index of the polyimide orientation layer is 1.68.

[0006] The groove width of the small groove is 136 nm, the groove height of the small groove is 138 nm, the groove height of the large groove is 112 nm, and the thickness of the polyimide orientation layer is 60 nm.

[0007] The slot width of the large slot is 740-835nm.

[0008] The minimum value of the modulation refractive index of the liquid crystal layer for the excitation incident light is not more than 1.5, and the maximum value is not less than 1.7.

[0009] The switch state of the surface plasmon switch is controlled by switching and adjusting the applied voltage.

[0010] Preferably, the liquid crystal layer is nematic liquid crystal material E7.

[0011] Preferably, the slot width of the large slot is 747nm, the refractive index of the liquid crystal layer is switched between 1.5 and 1.7 by switching and adjusting the applied voltage, and the switch state of the surface plasmon switch is controlled.

[0012] The present application has the following beneficial effects:

[0013] The present application provides a surface plasmon switch, which realizes flexible control of the surface plasmon switch by changing the refractive index of the liquid crystal by applying an applied voltage, has strong practicability, and has the characteristics of simple structure, convenient implementation, good switching characteristics, rapid response, and being conducive to small integration. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a side view of the surface plasmon switch of the present application;

[0015] Figure 2 is a surface plasmon electric field amplitude distribution diagram of the surface plasmon switch of the present application.

[0016] In the figure: 1, glass substrate; 2, gold film; 3, liquid crystal layer; 4, polyimide orientation layer; 5, PMMA polymer. DETAILED DESCRIPTION

[0017] To make the purpose, technical scheme and advantages of the present application clearer and more apparent, the following will combine specific embodiments and refer to the accompanying drawings Figures 1-2 The present application is further described in detail. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present application.

[0018] A surface plasmon switch, the structural schematic diagram of which is as shown in Figure 1As shown, it includes a glass substrate 1, the material of the glass substrate 1 is BK7 glass, a gold film 2 is provided on the glass substrate 1, the gold film 2 is provided with an asymmetric slit, the slit includes a small groove and a large groove, the side of one side of the small groove is aligned with the side of the same side of the large groove, the small groove and the large groove are both rectangular grooves, the small groove is located on the side close to the glass substrate 1, a PMMA polymer 5 is provided in the small groove, polyimide alignment layers 4 are provided on both sides of the large groove, and a liquid crystal layer 3 is provided in the rest of the large groove, the liquid crystal layer 3 is a nematic phase liquid crystal material E7, and the top surface of the gold film 2 A PMMA polymer 5 is provided, and the gold films 2 on both sides of the slit are isolated and insulated. An external voltage is provided on the gold films 2 on both sides of the slit. The liquid crystal layer 3 is in the electric field formed by the external voltage. The excitation incident light enters the surface plasmon switch normally from the small groove to the large groove. The excitation incident light is linearly polarized light with a wavelength of 700nm, and the polarization direction is perpendicular to the slit direction. For the excitation incident light, the refractive index of the glass substrate 1 is 1.52, the refractive index of the PMMA polymer 5 is 1.49, and the refractive index of the polyimide alignment layer 4 is 1.68.

[0019] like Figure 1 As shown, the specific parameters of the structure: the width of the small groove w 1 is 136nm, the height of the small groove h 1 is 138nm, the width of the large groove w 2 is 747nm, the groove height of the large groove h 2 is 112nm, the thickness of the polyimide alignment layer 4 w 3 is 60nm.

[0020] Figure 2 is the surface plasmon electric field amplitude distribution diagram of the surface plasmon switch of the present invention, wherein Figure 2 (a) is the surface plasmon electric field amplitude distribution diagram when the surface plasmon switch of the present invention is turned on, Figure 2 (b) is a graph showing the surface plasmon electric field amplitude distribution when the surface plasmon switch of the present invention is off. As can be seen from the figure, the surface plasmon electric field amplitude is strong in the on state and disappears in the off state. The excitation incident light amplitude is 1, and the surface plasmon electric field amplitude is obtained at a point 2 μm from the center of the small groove on the right side of the upper surface of the gold film 2 when the switch is on or off. When on, the electric field amplitude is 0.467, and when off, the electric field amplitude is 0.022. When the applied voltage is switched, the refractive index of the liquid crystal layer 3 switches between 1.5 and 1.7, causing the surface plasmon electric field amplitude at a point 2 μm from the center of the small groove on the right side of the upper surface of the gold film 2 to switch between 0.467 and 0.022. This allows for flexible control of the surface plasmon switch state by switching the applied voltage, making operation convenient.

[0021] The extinction ratio (ER) is introduced as an important parameter for measuring the performance of the surface plasmon switch, and the basic extinction ratio requirement for the performance of the surface plasmon switch is 10 dB, and the higher the extinction ratio is, the better the switching performance of the surface plasmon switch is, and the specific formula of ER is:

[0022]

[0023] Wherein, P1 and P0 respectively represent the light power when the surface plasmon switch is opened and closed, the light power is proportional to the square of the electric field amplitude, so by calculating the extinction ratio ER of the structure parameters of the present application is 26.57 dB, the extinction ratio result is the result of the cooperation of all the parameters of the technical scheme of the present application, and the extinction ratio is the optimal performance parameter that the technical scheme can achieve at present, so it can be seen that the performance of the surface plasmon switch provided by the present application is outstanding under the technical parameters.

[0024] The size of the slot width of the large slot is changed while keeping other technical parameters of the technical scheme of the present application unchanged, and the research results are shown in the following table 1: w 2

[0025] Table 1 Extinction ratio result display table of different large slot slot widths w 2

[0026] Large slot slot width w 2 / nm ]]> Minimum electric field amplitude Minimum electric field amplitude corresponding to the refractive index of the liquid crystal layer Maximum electric field amplitude Maximum electric field amplitude corresponding to the refractive index of the liquid crystal layer Extinction ratio / dB 700 0.431 1.7 0.49 1.5 1.1 705 0.43 1.7 0.493 1.5 1.2 710 0.375 1.7 0.492 1.5 2.4 715 0.372 1.7 0.495 1.5 2.5 720 0.285 1.7 0.488 1.5 4.7 725 0.278 1.7 0.491 1.5 4.9 730 0.164 1.7 0.48 1.5 9.3 735 0.155 1.7 0.483 1.5 9.9 740 0.034 1.7 0.466 1.5 22.7 745 0.025 1.7 0.469 1.5 25.5 750 0.021 1.68 0.445 1.5 26.5 755 0.026 1.68 0.448 1.5 24.7 760 0.052 1.66 0.415 1.5 18 765 0.045 1.64 0.418 1.5 19.4 770 0.029 1.62 0.373 1.5 22.2 775 0.022 1.62 0.376 1.5 24.7 780 0.034 1.6 0.355 1.7 20.4 785 0.033 1.6 0.359 1.7 20.7 790 0.053 1.56 0.398 1.7 17.5 795 0.047 1.56 0.401 1.7 18.6 800 0.043 1.54 0.43 1.7 20 805 0.036 1.54 0.432 1.7 21.6 810 0.05 1.52 0.453 1.7 19.1 815 0.045 1.52 0.454 1.7 20.1 820 0.068 1.5 0.467 1.7 16.7 825 0.063 1.5 0.468 1.7 17.4 830 0.146 1.5 0.479 1.7 10.3 835 0.146 1.5 0.48 1.7 10.3 840 0.228 1.5 0.489 1.7 6.6

[0027] From table 1, it can be obtained that when the slot width of the large slot w 2 is in the range of 740-835 nm, the extinction ratio meets the requirement of being greater than the basic extinction ratio 10 dB, which indicates that w 2 in the range of 740-835 nm, the performance of the surface plasmon switch of the present application meets the requirements.

Claims

1. A surface plasmon switch, characterized in that: The invention comprises a glass substrate (1), wherein the material of the glass substrate (1) is BK7 glass, a gold film (2) is provided on the glass substrate (1), and the gold film (2) is provided with an asymmetric slit, wherein the slit comprises a small groove and a large groove, and the side of one side of the small groove is aligned with the side of the same side of the large groove, and the small groove and the large groove are both rectangular grooves, and the small groove is located on a side close to the glass substrate (1), and a PMMA polymer (5) is provided in the small groove, and polyimide alignment layers (4) are provided on both sides of the large groove. The rest of the interior of the large groove is provided with a liquid crystal layer (3), the top surface of the gold film (2) is provided with the PMMA polymer (5), the gold films (2) on both sides of the slit are isolated and insulated, an external voltage is provided on the gold films (2) on both sides of the slit, the liquid crystal layer (3) is in an electric field formed by the external voltage, and the excitation incident light is incident normally from the small groove to the large groove into the surface plasmon switch, the excitation incident light is linearly polarized light with a wavelength of 700 nm, and the polarization direction is perpendicular to the slit direction; The width of the small groove is 136 nm, the height of the small groove is 138 nm, the height of the large groove is 112 nm, and the thickness of the polyimide alignment layer (4) is 60 nm; The groove width of the large groove is 740-835nm; The external voltage is switched and adjusted to control the switching state of the surface plasmon switch.

2. The surface plasmon switch according to claim 1, wherein: For the excitation incident light, the minimum value of the modulation refractive index of the liquid crystal layer (3) is not greater than 1.5, and the maximum value is not less than 1.

7.

3. The surface plasmon switch according to claim 1, wherein: The liquid crystal layer (3) is a nematic liquid crystal material E7.

4. The surface plasmon switch according to claim 1, wherein: The width of the large groove is 747 nm. By switching and adjusting the applied voltage, the refractive index of the liquid crystal layer (3) is switched between 1.5 and 1.7, thereby controlling the switching state of the surface plasmon switch.

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