CN110888189B - An ultrathin substrateless color-tunable surface plasmon filter - Google Patents

Abstract

The invention relates to the technical field of micro-nano integrated optical devices, and discloses an ultra-thin substrateless color-tunable surface plasmon filter. The filter structure includes: a waveguide layer, a buffer layer and a rectangular metal nanodisk array. The waveguide layer is covered with a buffer layer, and the buffer layer is etched with a uniformly arranged rectangular metal nanodisk array. The period of the rectangular metal nanodisk array in the x direction is P _x , and the period in the y direction is P _y . When x and y are equal, the static modulation of the filtered color can be realized by changing the period in the x(y) direction. When x and y are not equal, the static modulation of the filtered color can be realized by changing the period, and the polarization of light can be changed. to achieve dynamic modulation of the filtered color. This patent has the advantages of small size, high transmission efficiency, simple structure design, can realize static modulation and dynamic modulation of color at the same time, can fix TE(TM) polarization to filter out color, and modulate the color filtered out under TM(TE) polarization separately, etc. advantage. The invention has important applications in the fields of future photoelectric device integration, ultra-high resolution imaging, LCD liquid crystal display system and the like.

Description

An ultrathin substrateless color-tunable surface plasmon filter

(1) Technical field

The invention relates to the technical field of micro-nano integrated optical devices, in particular to an ultra-thin substrateless color-tunable surface plasmon filter.

(2) Background technology

In nature, many substances have beautiful and rich colors. They diffract, reflect and scatter light through special microstructures on their surfaces to take on different colors. Surface plasmon is the cluster oscillation of metal free charges induced by light on the metal surface. By changing the shape and size of the plasmonic metal nanostructure, the excitation of surface plasmon is controlled, so as to achieve the frequency-selective frequency of visible light. Effect.

With the development of micro-nano processing technology, in recent years, artificial fabrication of micro-nano metal structures is the main source of structural color. Compared with traditional chemical dyes, structural colors are recyclable, easy to manufacture and durable. In addition, the local effect of secondary diffraction of plasmons can break through the diffraction limit and improve imaging resolution. . These properties make surface plasmon structure color play an important role in ultra-high-resolution imaging, LCD liquid crystal display systems, CMOS digital integrated circuits, and light-emitting diodes.

With the in-depth research on plasmonic structural colors and the demand for scientific and technological development, a large number of problems have been raised, such as how to improve the anti-oxidation and anti-vulcanization properties of the device to prolong its service life, how to achieve large-scale, Mass production; the plasmon structure color on the surface can realize dynamic regulation, etc.

In order to solve the problem of dynamic regulation of surface plasmon structural color, this paper provides a transmissive color tunable filter composed of a metal nanodisk array, a buffer layer and a waveguide. The transmission efficiency of the proposed filter can reach more than 70%. The static modulation of color can be realized by changing the structure size and period, and the dynamic modulation of color can be realized by changing the light polarization.

(3) Contents of the invention

In view of the above problems, the purpose of the present invention is to provide an ultra-thin substrateless surface plasmon filter with tunable color. Light enters the filter from the positive z-axis direction, and the filtered light exits from the negative z-axis direction. Static modulation of the filtered color can be achieved by controlling the period of the rectangular metal nanodisk array, and dynamic modulation of the filtered color can be achieved by controlling the polarization of the incident light, which enables manipulation of light covering the entire visible spectrum.

To achieve the above object, the present invention adopts the following technical solutions:

An ultra-thin substrateless color-tunable surface plasmon filter consists of a waveguide layer, a buffer layer and a rectangular metal nanodisk. Arranged rectangular metal nanodisk arrays.

In the above scheme, it is preferred that the material of the waveguide layer is Si ₃ N ₄ and its thickness H ₁ is fixed at 100 nm, the buffer layer material is MgF ₂ , and the thickness H ₂ is fixed at 25 nm, and the rectangular metal nanodisk is selected as Al, and its thickness H ₃ is fixed. is 40nm.

P _x is the period in the x direction of the rectangular Al nanodisk, P _y is the period in the y direction of the rectangular Al nanodisk, and the duty cycle of the rectangular Al nanodisk directly affects the transmission efficiency and the saturation of the filtered color. The duty cycle of the nanodisks in both the x and y directions is 0.7.

The present invention has the following advantages due to taking the above technical solutions:

The present invention provides an ultra-thin substrateless color-tunable surface plasmon filter. Al is selected as the metal material. Compared with the commonly used Ag material, Al is common and cheap, and has lower inter-band transition. loss, as well as better antioxidant capacity, have wider applications in practice.

The ultra-thin substrateless color-tunable surface plasmon filter provided by the present invention, compared with the common solid-state color filter, can not only realize solid-state color-tuning by changing the period of the Al nanodisk, but also can achieve solid-state color-tuning. Change the polarization angle of incident light to achieve dynamic modulation of color.

The invention provides an ultra-thin substrateless color-tunable surface plasmon filter, which has polarization-sensitive characteristics, and can realize dynamic modulation of the filtered color by modulating the polarization angle of incident light. Compared with the filter that uses liquid crystal to realize dynamic color adjustment, the present invention can overcome the disadvantages of the liquid crystal color adjustment filter being complicated in structure, difficult to realize large-area manufacturing, large in structure size, unfavorable for optoelectronic integration, and difficult to control color. Compared with a filter that also uses polarization to modulate color, the present invention provides an ultra-thin substrateless color-tunable surface plasmon filter, which has fixed TE(TM) polarization color and a single control of TM(TE) color. The advantages of color under polarization.

(4) Description of drawings

Figure 1 is a schematic structural diagram of an ultra-thin substrateless color-tunable surface plasmon filter.

Fig. 2(a) is the transmission spectrum of the period P _x = P _y and P _x = P _y changing from 300 nm to 600 nm with a step size of 50 nm, and Fig. 2(b) is the CIE corresponding to Fig. 2(a) Chromatogram.

Fig. 3 is the transmission spectrum when the light incident angle theta is changed from 0° to 30° in 10° steps when the period in the x and y directions is fixed at P _x =P _y =400nm.

Figure 4(a) is the transmission spectrum when the period P _x in the x direction is fixed at 300 nm and the polarization angle phi = 0°, and the period P _y in the y direction changes from 300 nm to 600 nm in steps of 50 nm. When the x-direction period P _x =400nm and the polarization angle phi=0°, the y-direction period P _y changes from 300nm to 600nm with a step size of 50nm. b) The corresponding CIE chromatogram.

Figure 5(a) is the transmission spectrum when the polarization angle phi is changed from 0° to 90° in 22.5° steps when P _x = 300 nm and P _y = 400 nm are fixed, and Figure 5(b) is the fixed P _x = 300 nm , when P _y = 500 nm, the transmission spectrum when the polarization angle phi changes from 0° to 90° in 22.5° steps, Figure 5(c) is the CIE chromatogram corresponding to Figures 5(a) and 5(b) .

The labels in the figure are: 1 waveguide layer, 2 buffer layer, 3 rectangular metal nanodisks

(5) Specific implementation manner

The present invention will be described in more detail below in conjunction with the accompanying drawings:

Referring to FIG. 1, an ultra-thin substrateless color-tunable surface plasmon filter includes a waveguide layer, a buffer layer 2 covering the waveguide layer 1, and uniformly arranged rectangular metal nanometers are etched on the buffer layer 2. disk array 3.

The material of the waveguide layer 1 is Si ₃ N ₄ , the material of the buffer layer 2 is MgF ₂ , and the material of the rectangular metal nanodisk array is Al. Compared with the metal Ag with the lowest loss in the visible spectrum, Al is easy to obtain and cheap, and has a lower cost. The inter-band transition loss, and better anti-oxidation, anti-corrosion ability.

The thickness H1 of the waveguide layer is fixed at ₁₀₀ nm, the thickness _H2 of the buffer layer is fixed at 25 nm, the thickness H3 _of the rectangular metal nanodisk is fixed at 40 nm, the period of the rectangular metal nanodisk in the x direction is _Px , and the period in the y direction is _Py , The duty cycle of the nanodisks in the x and y directions is fixed at 0.7.

The three-dimensional finite difference time domain (FDTD) method is used to numerically simulate the structure. The FDTD boundary conditions are set as, the positive and negative z directions are set as the perfect matching layer (PML), and the positive and negative directions of x and y are set as periodic boundary conditions. After the test, the grid size in the positive and negative directions of x, y, and z is set to 5nm*5nm*2nm. The transmission coefficient T is defined as, T=Pout/Pin where Pin and Pout are the input and output power, respectively.

Figure 2(a) is an ultra-thin substrateless color-tunable surface plasmon filter. Under the conditions of period P _x =P _y in the x and y directions and polarization angle phi = 0, P _x (P _y ) Transmission spectrum when switching from 300 nm to 600 nm in 50 nm steps. Figure 2(b) is a CIE chromatogram corresponding to the transmission spectrum of Figure 2(a). It can be seen from Fig. 2(a) that with the increase of the period P _x (P _y ) in the x(y) direction, the transmission spectrum is red-shifted, that is, the filtered color gradually changes from the blue band to the red band. Fig. 2(a) can also see that the transmission efficiency of the filter (the wavelength at the highest transmittance) is greater than 70%, which indicates that the transmission efficiency of the filter is very high and the filtering effect is guaranteed. A more intuitive color change can be seen from Figure 2(b), and from Figure 2(b), it can be known that the filter can achieve all-optical regulation in visible light.

As shown in Fig. 3, it is an ultra-thin substrateless color tunable surface plasmon filter, under the conditions of x, y direction period P _x =P _y =400nm, polarization angle phi = 0, with 10° The step size transforms the transmission spectrum at the incident angle theta from 0° to 30°. It can be seen from Figure 3 that the filter is extremely sensitive to the incident angle and has little tolerance to the angle. Therefore, in the actual manufacturing process, in order to reduce the error, it is necessary to ensure that the incident light angle is vertically incident without deviation.

As shown in Figure 4(a), it is an ultra-thin substrateless color-tunable surface plasmon filter with a fixed x-direction period P _x = 300 nm and a polarization angle phi = 0°, the y-direction period P The transmission spectrum of _y changing from 300 nm to 600 nm in 50 nm steps. As the period P _y in the y direction increases gradually, the peak of the main peak of the transmission spectrum in Fig. 4(a) does not change, indicating that the filtered color does not change much. . Figure 4(b) is the transmission spectrum of the period P _y in the y direction changing from 300 nm to 600 nm in steps of 50 nm when the period P _x in the x direction is fixed at 400 nm and the polarization angle phi = 0°. _y increases gradually, and the peak value of the main peak of the transmission spectrum in Fig. 4(b) does not change, indicating that the filtered color does not change much. 4(c) is the CIE chromatogram corresponding to Figures 4(a) and 4(b). From the figure, it can be seen more intuitively that the filtered colors are concentrated in a small range, and the color is basically unchanged. Therefore, when the polarization angle of the filter is 0°, the period P _x in the x-direction mainly determines the filtered color, while the period P _y in the y-direction has little effect on the filtered color.

As shown in Figure 5(a), it is an ultra-thin substrateless color-tunable surface plasmon filter with a fixed x-direction period P _x = 300 nm, y-direction period P _y = 400 nm, and the polarization angle is 22.5°. When the step size increases from 0° to 90°, the peaks between wavelengths 400-500 nm gradually decrease, and new peaks appear between wavelengths 500-600 nm, and the peaks gradually increase with the increase of the polarization angle. Figure 5(b) is a transmission spectrum when the polarization angle is increased from 0° to 90° in steps of 22.5° with a fixed x-direction period Px=300 nm and a y-direction period _Py of 500 nm. With the increase of the polarization angle, the wave peak between the wavelengths of 400nm and 500nm gradually decreases, and a transmission peak appears between the wavelengths of 600nm and 700nm, and increases accordingly. Figure 5(c) is the CIE chromatogram corresponding to Figures 5(a) and 5(b). It can be clearly seen that the color changes with the change of the polarization angle.

The ultra-thin substrateless color-tunable surface plasmon filter of the present invention can realize the manipulation of light covering the entire visible spectrum by changing the period in the x and y directions and realize static modulation. Since the present invention is sensitive to polarization, when the periods of the x and y directions are different, the dynamic modulation of the color can be realized by changing the polarization angle. The filter of the invention can achieve a transmittance of more than 70%, has a very small thickness, and can play a great role in high-resolution color display and integrated optoelectronic devices and the like.

The preferred embodiments of the present invention have been specifically described above, but the present invention is not limited to the embodiments, and those skilled in the art can also make various equivalent modifications or Alternatives, such equivalent modifications or substitutions are all included within the scope of this application.

Claims (1)

1. The ultrathin substrate-free surface plasma filter with tunable colors comprises a waveguide layer (1), a buffer layer (2) covering the waveguide layer (1), and rectangular metal nano-discs (3) which are uniformly distributed and etched on the buffer layer (2), wherein the waveguide layer (1) is made of Si₃N₄Thickness H of₁Fixed at 100nm, and MgF is selected as the material of the buffer layer (2)₂Thickness H of₂The array metal material of the rectangular metal nano disc (3) is Al and the thickness H is fixed to be 25nm₃Fixed at 40nm, and the period of the rectangular metal nano disc (3) array in the x direction is P_xWith period in y direction of P_yThe duty ratio of the x direction and the y direction of the array of the fixed rectangular metal nanometer disc (3) is 0.7.

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