CN211956048U - Surface plasma optical switch based on periodic circular ring-slit composite hole array - Google Patents

Abstract

A surface plasmon optical switch based on a periodic ring-slit composite hole array is composed of a dielectric substrate and a metal thin film. The metal thin film is arranged directly above the dielectric substrate, and a plurality of rings arranged in a periodic array are arranged on the metal thin film. - Slit unit, circular ring - The slit unit includes a circular ring and a rectangular slit running through the thickness direction of the metal film, the rectangular slit is located in the circular ring, is perpendicular to the array period direction, and the center of the rectangular slit coincides with the circular center of the circular ring . The performance of the surface plasmon optical switch was optimized by changing the polarization direction of the incident light, the thickness of the metal film, and the length of the ring-slit unit interval. The invention has the advantages of simple structure, low manufacturing process requirements, small size and convenient integration; no interference of the pump light on the signal light and subsequent optical paths, the switching ratio of the visible light band and the near-infrared band can be effectively controlled, and the operation is convenient. Low power consumption.

Description

Surface Plasmon Optical Switch Based on Periodic Ring-Slit Composite Hole Array

technical field

The invention relates to the field of micro-nano photonic devices, in particular to a surface plasmon optical switch based on a periodic ring-slit composite hole array.

Background technique

With the development of society, electronic devices have been difficult to meet people's demand for information transmission speed and storage capacity. Since surface plasmons (SPs) have the characteristics of subwavelength, localized electric field and localized field enhancement, the use of surface plasmons can solve the current diffraction limit problem, enabling the miniaturization and integration of photonic devices. It greatly expands the application of photonic devices in the field of information transmission. Moreover, the surface plasmon optical switch changes the excitation or transmission of SPs in the switch by controlling external factors, thereby regulating the presence or absence of light, thereby realizing the switching operation of light. Compared with the traditional optical switch, the surface plasmon optical switch can be used. The control of light is realized at scales smaller than the diffraction limit, and the integration of optical switches is realized at the nanoscale.

In recent years, with the maturity of various micro-nano fabrication technologies, many surface plasmon optical switches have been realized successively. For example, Pala R.A. et al. added a photochromic molecular layer on the surface of a metal thin film on a dielectric substrate, and set two gratings in the metal thin film, and used pump light to illuminate the photochromic molecular layer to realize the surface plasmon polariton waveguide optical switch. Veronis G et al. realized a metal-air-metal waveguide surface plasmon optical switch controlled by external pump light by setting a semiconductor gain medium rectangular cavity in the waveguide. Chinese invention patent ZL201710497191.0 discloses a surface plasmon optical switch based on periodic subwavelength hole arrays. However, the above-mentioned current surface plasmon optical switches have complex structures and are difficult to integrate, and the fabrication accuracy at the nanoscale increases the fabrication difficulty; and due to the need for external pump light control, the pump light interferes with the signal light and subsequent optical paths; in addition, , the switching ratio of the surface plasmon optical switch is low, no more than 10dB, which makes the surface plasmon optical switch loss larger and affects the overall performance parameters of the surface plasmon optical switch.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a surface plasmon optical switch based on a periodic ring-slit composite hole array. The surface plasmon optical switch has a simple structure, is easy to manufacture, and has no pump light. interference, and has a high switching ratio, which can be applied to surface plasmon optical switches in the visible light band and the near-infrared band.

The technical scheme of the present invention is as follows: a surface plasmon optical switch based on a periodic ring-slit composite hole array is a micro-nano structure composed of a dielectric substrate and a metal thin film. There are a plurality of ring-slit units on it, and the plurality of ring-slit units are arranged in a periodic array on the metal film. The ring-slit unit includes a ring running through the thickness direction of the metal film and a A rectangular slit in the thickness direction of the film and perpendicular to the periodic direction of the transverse array, the rectangular slit is located in the ring, and the center of the rectangular slit coincides with the center of the ring.

A further technical solution of the present invention is: the dielectric material of the dielectric substrate is quartz or benzocyclobutene, the thickness of the dielectric substrate is 150nm-250nm; the material of the metal film is silver or gold, and the metal film The thickness of 50nm ~ 100nm.

A further technical solution of the present invention is: the number of the ring-slit units is not less than 9, the shape of the array formed by the arrangement of the plurality of ring-slit units is a square or a rectangle, and the shape of the plurality of ring-slit units The arrangement period is 500nm～800nm.

A further technical solution of the present invention is: the inner radius of the ring is 100-150 nm, the width of the ring is 25-55 nm; the length of the slit is 100-250 nm, and the width is 25-60 nm; is less than the inner diameter of the ring.

Compared with the prior art, the present invention has the following characteristics:

1. The surface plasmon optical switch of the present invention is only composed of a dielectric substrate and a metal thin film with a hole array, and is small in size, simple in structure and easy to manufacture.

2. The surface plasmon optical switch of the present invention can effectively control the switch of visible light band and near-infrared band light only by changing the polarization direction of the incident light, which expands the application place and adaptable range of the surface plasmon optical switch, and is easy to operate , without the interference of the pump light to the signal light and subsequent optical paths.

3. The surface plasmon optical switch of the present invention can effectively adjust the switching ratio of the surface plasmon optical switch by changing the polarization direction of the incident light, so that the surface plasmon optical switch has a higher switching ratio and effectively reduces the surface plasmon light The energy consumption of the switch is improved, and the performance of the surface plasmon optical switch is improved.

The detailed structure of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

Description of drawings

Fig. 1 is the structural representation of the present invention;

Fig. 2 is a two-dimensional side cross-sectional schematic diagram of a ring-slit unit;

3 is a cross-sectional view of a ring-slit unit;

Fig. 4 is the transmittance spectrum of the first embodiment of the present invention in the visible light band;

Fig. 5 is the transmittance spectrum of the first embodiment of the present invention in the near-infrared band;

6 is the transmittance spectrum of the second embodiment of the present invention in the visible light band;

Fig. 7 is the transmittance spectrum of the second embodiment of the present invention in the near-infrared band;

Fig. 8 is the transmittance spectrum of the third embodiment of the present invention in the visible light band;

Fig. 9 is the transmittance spectrum of the third embodiment of the present invention in the near-infrared band;

FIG. 10 is the transmittance spectrum of the fourth embodiment of the present invention in the optical communication band.

Detailed ways

Embodiment 1, as shown in FIG. 1, the surface plasmon optical switch based on the periodic ring-slit composite hole array is a micro-nano structure composed of a dielectric substrate 1 and a metal film 2, and the metal film 2 is arranged on the dielectric substrate. 1 directly above.

The dielectric material of the dielectric substrate is quartz, and the thickness of the quartz is 150 nm. The dielectric material of the dielectric substrate can also be any other dielectric suitable for processing, such as benzocyclobutene and the like.

The material of the metal thin film is gold, and the thickness of gold, which is the material of the metal thin film, is 50 nm. The material of the metal thin film can also be other metals that can generate surface plasmons, such as silver.

The metal film 2 is provided with 9 ring-slit units 3, the 9 ring-slit units 3 are arranged in a periodic array on the metal film 2, and the 9 ring-slit units 3 are arranged according to 3×3. They are arranged on the dielectric substrate 1 in a square manner, and the arrangement period is 600 nm.

The ring-slit unit 3 includes a ring 3.1 that runs through the thickness direction of the metal film and a rectangular slit 3.2 that penetrates the thickness direction of the metal film and is perpendicular to the lateral array period direction of the ring-slit unit 3. The rectangular slit 3.2 The center of the rectangular slit 3.2 is located within the ring 3.1 and coincides with the center of the ring 3.1. The inner radius of the ring 3.1 is 100 nm, and the width of the ring 3.1 is 25 nm, that is, the outer radius of the ring 3.1 is 125 nm. The slit 3.2 has a length of 150 nm and a width of 30 nm.

The surface plasmon optical switch based on the periodic ring-slit composite hole array is defined in the X, Y, Z Cartesian orthogonal coordinate system, wherein the X axis and the Z axis are the transverse array period direction and the longitudinal array period direction respectively. , the Y axis is perpendicular to the plane formed by the X and Z axes, K is the incident light, L is the transmitted light, and E is the direction of the electric field intensity of the incident light. The incident light K is vertically incident on the bottom side of the metal film 2 from the direction of the dielectric substrate 1, and is transmitted from the other side of the metal film 2 to form the transmitted light L. When the polarization direction of the incident light K is along the X-axis direction, the surface plasmon The bulk optical switch is in the "on" state; when the polarization direction of the incident light K is along the Z-axis direction, the surface plasmon optical switch is in the "off" state. It is a well-known technique in the art to change the polarization direction of the incident light K.

In addition, those skilled in the art know that when the polarization direction of the incident light K is along the X-axis direction, that is, when the longitudinal direction of the rectangular slit 3.2 is perpendicular to the polarization direction of the incident light K, the rectangular slit 3.2 generates surface plasmon (Surface Plasmon Polariton , SPP) resonance, and the SPP resonance phenomenon can be observed in the visible light band (wavelength is 400nm-750nm) of the transmitted light L transmission spectrum. When the polarization direction of the incident light K is along the Z-axis direction, that is, when the length direction of the rectangular slit 3.2 is parallel to the polarization direction of the incident light K, the rectangular slit 3.2 cannot excite the SPP resonance. In the visible light band (wavelength is 400nm ~ 750nm) of the transmitted light L transmission spectrum, no matter which direction the polarization direction of the incident light K is, the ring 3.1 has SPP resonance, but this SPP resonance is very weak and is not enough to affect the surface plasmon switching. Effect.

The polarization direction of the incident light K is along the X-axis direction. When the length direction of the rectangular slit 3.2 is perpendicular to the polarization direction of the incident light K, the localized surface plasmon (LSP) resonance of the rectangular slit 3.2 is the highest. Strong, the LSP resonance phenomenon can be observed in the near-infrared band (wavelength is 750nm ~ 1600nm) of the transmission spectrum of the transmitted light L; when the length direction of the rectangular slit 3.2 is parallel to the polarization direction of the incident light K, the rectangular slit 3.2 does not LSP resonance is present. No matter which direction the polarization direction of the incident light K is, the ring 3.1 hardly forms LSP resonance in this band.

As shown in FIG. 1 , the incident light K is vertically incident on the bottom side of the metal thin film 2 from the direction of the dielectric substrate 1 , and a surface plasmon effect is generated in the ring-slit unit 3 of the metal thin film 2 , and is emitted from the other side of the metal thin film 2 side transmission. Change the polarization direction of the incident light K, and then control whether SPP or LSP resonance occurs in the rectangular slit 3.2 in the ring-slit unit 3, so that the surface plasmon optical switch structure based on the periodic ring-slit composite hole array can be used. The transmittances of the plurality of ring-slit units 3 arranged in a periodic array in the visible light band and the near-infrared band are changed, and the optical switching operation in the visible light band and the near-infrared band based on surface plasmon is realized. Figures 4-5 show the transmittance spectrum in the visible light band and the near-infrared band, respectively. It can be seen from Figure 4 that the switching wavelength λ ₀ in the visible light band is 619 nm, the transmission peak value T _on at λ ₀ when the optical switch is on is 0.5824, and the transmittance at λ ₀ when the optical switch is off T _off is only 0.05716, on/off ratio = 10lg(T _on /T _off ) = 10.08dB; at this time, the ratio of the total energy stored in the surface plasmon optical switch per unit time to the energy lost per unit time, that is, the quality factor Q is about equals 30. It can be seen from Figure 5 that the switching wavelength λ ₀ in the near-infrared band is 1064 nm, the transmission peak value T _on at λ ₀ when the optical switch is on is 0.3978, and the transmittance at λ ₀ when the optical switch is off T _off is only 0.01057, and the switching ratio=10lg(T _on /T _off )=15.6dB.

The second embodiment is similar in structure to the first embodiment, except that the dielectric substrate 1 is made of quartz with a thickness of 225 nm; the metal thin film 2 is made of silver with a thickness of 55 nm. The arrangement period of the ring-slit unit 3 is 700 nm, the length and width of the slit are 100 nm and 25 nm, respectively, and the inner and outer radii of the ring are 120 nm and 175 nm, respectively. 6-7 respectively show the transmittance spectrum of the surface plasmon optical switch in the second embodiment in the visible light band and the near-infrared band. It can be seen from Fig. 6 that the switching wavelength λ ₀ in the visible light band is 631 nm, the transmission peak value T _on at λ ₀ when the optical switch is on is 0.5697, and the transmittance T at λ ₀ when the optical switch is off _off is only 0.05596, on/off ratio=10lg(T _on /T _off )=10dB; at this time, the ratio of the total energy stored per unit time to the energy lost per unit time of the surface plasmon optical switch, that is, the quality factor Q is approximately equal to 31 . It can be seen from Figure 7 that the switching wavelength λ ₀ in the near-infrared band is 1087 nm, the transmission peak value T _on at λ ₀ when the optical switch is on is 0.4986, and the transmittance at λ ₀ when the optical switch is off T _off is only 0.0119, and the switching ratio=10lg(T _on /T _off )=16.23dB.

The third embodiment is similar in structure to the first embodiment, except that: the dielectric substrate 1 is made of quartz with a thickness of 250 nm; the metal thin film 2 is made of silver with a thickness of 100 nm. The arrangement period of the ring-slit unit 3 is 800 nm, the length and width of the slit are 250 nm and 60 nm, respectively, and the inner and outer radii of the ring are 150 nm and 200 nm, respectively. 8-9 show the transmittance spectrum of the surface plasmon optical switch of Embodiment 3 in the visible light band and the near-infrared band. It can be seen from Fig. 8 that the switching wavelength λ ₀ in the visible light band is 640 nm at this time, the transmission peak value T _on at λ ₀ when the optical switch is on is 0.5536, and the transmittance T at λ ₀ when the optical switch is off _off is only 0.05418, on/off ratio=10lg(T _on /T _off )=10.09dB; at this time, the ratio of the total energy stored per unit time to the energy lost per unit time of the surface plasmon optical switch, that is, the quality factor Q is approximately equal to 32. It can be seen from Figure 9 that the switching wavelength λ ₀ in the near-infrared band is 1092 nm at this time, the transmission peak value T _on at λ ₀ when the optical switch is on is 0.5366, and the transmittance at λ ₀ when the optical switch is off T _off is only 0.0126, and the switching ratio=10lg(T _on /T _off )=16.29dB.

The fourth embodiment is similar in structure to the first embodiment, except that the dielectric substrate 1 is made of quartz with a thickness of 225 nm; the metal thin film 2 is made of silver with a thickness of 50 nm. The arrangement period of the ring-slit unit 3 is 600 nm, the length and width of the slit are 100 nm and 25 nm, respectively, and the inner and outer radii of the ring are 121 nm and 175 nm, respectively. FIG. 10 shows the transmittance spectrum of the fourth embodiment when used in an optical communication environment. It can be seen from Fig. 10 that the switching wavelength λ ₀ in the visible light band is 1310 nm at this time, the transmission peak value T _on at λ ₀ when the optical switch is on is 0.9154, and the transmittance at λ ₀ when the optical switch is off T _off is only 0.01518, and the switching ratio=10lg(T _on /T _off )= 17.8dB. It can be seen from this that the surface plasmon optical switch of this embodiment realizes the switching operation of 1310 nm light in the near-infrared band, indicating that the Surface plasmon optical switches can be applied in the field of optical communication.

Comparative Experiment:

In order to further compare the performance of the surface plasmon optical switch based on the periodic ring-slit composite hole array, in the visible light band and the near-infrared band, the state-of-the-art surface plasmon based on the periodic ring-slit composite hole array was compared. The optical switch and the surface plasmon optical switch based on the periodic circular four-point hole array are experimentally compared in their on-state quality factors and on-off ratios, respectively. The comparison results are shown in Table 1 below.

Table 1 Comparative analysis results of two types of surface plasmon optical switches

From the analysis in Table 1, it can be known that the surface plasmon optical switch based on the periodic circular four-point hole array has no optical switching capability in the visible light band (500nm ~ 750nm), while the surface plasmon optical switch based on the periodic circular ring-slit composite hole array has no optical switching capability. The switch has high quality factor and optical switching capability with high switching ratio. In the near-infrared band (750nm～1600nm), the quality factor of the surface plasmon optical switch based on the periodic ring-slit composite hole array is nearly 7 higher than that of the surface plasmon optical switch based on the periodic circular four-point hole array. , the switch ratio is nearly 6dB higher, which greatly improves the performance parameters of the optical switch. At the same time, the fabrication of surface plasmon optical switches based on periodic circular four-point hole arrays is very complicated in the micro-nano field, which requires high precision of the lithography machine. The switch is relatively easy to make in shape, and the requirements for the equipment are not high.

The above is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. Any person skilled in the art can easily think of changes or Substitutions should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (4)

1. The surface plasma optical switch based on the periodic circular ring-slit composite hole array is a micro-nano structure consisting of a dielectric substrate and a metal film, wherein the metal film is arranged right above the dielectric substrate, and the surface plasma optical switch is characterized in that: the metal film is provided with a plurality of ring-slit units, the plurality of ring-slit units are periodically arrayed on the metal film, each ring-slit unit comprises a ring penetrating through the thickness direction of the metal film and a rectangular slit penetrating through the thickness direction of the metal film and perpendicular to the transverse array period direction, the rectangular slits are located in the rings, and the centers of the rectangular slits are overlapped with the circle centers of the rings.

2. The surface plasma optical switch based on the periodic ring-slit composite hole array as claimed in claim 1, wherein: the dielectric material of the dielectric substrate is quartz or benzocyclobutene, and the thickness of the dielectric substrate is 150 nm-250 nm; the metal film is made of silver or gold, and the thickness of the metal film is 50 nm-100 nm.

3. The surface plasma optical switch based on the periodic ring-slit composite hole array as claimed in claim 1, wherein: the number of the ring-slit units is not less than 9, the array formed by the arrangement of the plurality of ring-slit units is square or rectangular, and the arrangement period of the plurality of ring-slit units is 500 nm-800 nm.

4. The surface plasma optical switch based on the periodic ring-slit composite hole array as claimed in claim 1, wherein: the inner circle radius of the circular ring is 100-150 nm, and the width of the circular ring is 25-55 nm; the length of the slit is 100-250 nm, and the width of the slit is 25-60 nm; the length of the slit is smaller than the diameter of the inner circle of the circular ring.

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