WO2014082515A1

WO2014082515A1 - Surface plasmon filter and preparation method therefor

Info

Publication number: WO2014082515A1
Application number: PCT/CN2013/086045
Authority: WO
Inventors: 司光远; 姜潇潇; 谷琼婵
Original assignee: 东北大学
Priority date: 2012-11-13
Filing date: 2013-10-28
Publication date: 2014-06-05
Also published as: CN102981199A

Abstract

The present invention relates to the technical field of optical devices. Provided is a surface plasmon filter and a preparation method therefor. The surface plasmon filter comprises: a base material (11); a metallic film (21) attached to the base material; the metallic film is provided with a plurality of annular hollow structures (31). Providing a plurality of annular hollow structures on the metallic film and utilizing the high degree of symmetry of said structures, allows the surface plasmon filter to solve the problem of polarization sensitivity in filters having notch antennas (23) and layer-stacked linear gratings (24), and thereby gives such filters wider scope for application and makes them better able to adapt to non-polarized natural light.

Description

TECHNICAL FIELD The present invention relates to the field of optical functional devices, and in particular to a surface plasmon filter and a method of fabricating the surface plasmon filter. Background technique

Since the French scientist Ebbesen et al. first discovered the extraordinary optical transmission (EOT) in metal subwavelength structure in 1998, the surface plasmon principle has high resolution, easy modulation and excellent performance. Other advantages have been widely used in the fields of optoelectronics, new energy (solar cells), data storage, and microscopic imaging. Among them, especially the surface plasmon filter device is the fastest developed, and the application foreground is also the most extensive. British scientists Pendry proposed super-lens with negative refractive index and the concept of stealth conditions through coordinate transformation methods in 2000 and 2006 respectively, which enabled the scientific community to re-recognize and examine the abnormal electromagnetic properties and stealth effects of supernormal media and their related applications. Subsequently, the Ebbesen team again proposed in 2008 to use a linear groove antenna with a periodic structure to filter the Broadband white light source, opening a new era for the development of filter devices.

The structure of the surface plasmon filter designed by Ebbesen et al. is shown in FIG. 1a: in a 300 nm thick silver film, a slit having a width of 170 nm (ie, a nano slit) is formed, and at the upper end of the nano slit 22, Four slots having different depths are respectively etched on both sides; the four slots on both sides of the nano slit can function as an antenna (ie, a groove antenna) for collecting the light signal transmitted through the nano slit 22, and transmitting the light The peak position of the signal is closely related to the period size of the groove antenna 23. Therefore, by using the groove antennas 23 of different periods, the wavelength of light transmitted through the nano slits 22 can be precisely controlled, thereby achieving the effect of splitting.

Subsequently, in 2010, LJay Guo's group proposed the use of one-dimensional metal-insulator-metal

(Metal-Insulator-Metal, abbreviated as MIM) layer stack linear grating structure for broadband white light source The splitting is performed; the structure is as shown in FIG. 1b, wherein the one-dimensional periodic stack linear grating structure 24 is also wavelength selective for the white light source, and the position of the peak can be precisely controlled by the period of the modulation grating. Then, the researchers in the same research group embedded a similar filter structure into the organic solar cell, and obtained a very good energy capture effect. Subsequently, photonic crystal filters, silicon nanowire filters, and "cross-shaped" filters have been reported, making similar devices fully researched and attracted widespread attention in the scientific community.

However, in the prior art, whether it is a one-dimensional slot antenna, a layer stack linear grating structure or a "cross-shaped" structure, there is a strong selection requirement for the polarization direction of the incident light source. This is because the one-dimensional slot antenna, the layer stack linear grating and the like are themselves asymmetric structures, so the spectroscopic effect is only obtained when the direction of the incident optical field is parallel to the groove or grating (that is, Transverse-Magneticwave). In real life, most of the light sources are unpolarized natural light (such as sunlight). Therefore, the polarization selectivity of the above structure greatly limits the range of application of such a filter device. In addition, since the polarization sensitivity causes a part of the light energy to be transmitted through the filter but is reflected or absorbed, the transmission efficiency of the filter of the above structure is low, and the performance of the filter is lowered. Summary of the invention

(1) Technical problems to be solved

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface plasmon filter that has a wider range of applications and is more adaptable to non-polarized natural light and a method of fabricating the surface plasmon filter, in view of some or all of the problems in the background art.

(2) Technical plan

The technical scheme of the present invention is as follows:

A surface plasmon filter comprising: a base material and a metal film attached to the base material; and the metal film is provided with a plurality of annular hollow structures.

Preferably, the number of the annular hollow structures is one.

Preferably, the number of the annular hollow structures is plural, and the plurality of annular hollow structures are arranged in an array. Preferably, the difference between the outer diameter and the inner diameter of each of the annular hollow structures is related to the wavelength of the monochromatic light selectively transmitted by the surface plasmon filter.

Preferably, the difference between the outer diameter and the inner diameter of each of the annular hollow structures is not less than 10 nm and not more than 160 nm.

Preferably, the planar formant of the surface plasmon filter is located in the near infrared band. Preferably, the metal film is made of gold, silver, a platinum group metal or an aluminum group metal.

Preferably, the base material is quartz or glass.

The invention also provides a method for preparing any of the above surface plasmon filters: A method for preparing a surface plasmon filter, comprising:

Step 1: forming a metal film on the base material;

Step 2: forming a plurality of annular hollow structures on the metal film.

Preferably, the step 2 further includes:

A plurality of annular hollow structures are formed on the metal film using a focused ion etching method. (3) Beneficial effects

The surface plasmon filter provided by the embodiment of the invention solves, for example, a four-slot antenna and a layer stack linear grating by opening a plurality of annular hollow structures on the metal film and utilizing the highly symmetrical characteristics of the annular hollow structure. The polarization sensitivity problem that is common in filters makes the application of filter-like devices wider and more suitable for non-polarized natural light. DRAWINGS

Figure la is a schematic structural view of a groove antenna type filter in the prior art;

Figure lb is a schematic structural view of a layer stack linear grating filter in the prior art;

2a is a schematic structural view of a surface plasmon filter according to an embodiment of the present invention; and FIG. 2b is a plan view of a single nano ring structure of FIG. 2;

Figure 2c is a cross-sectional view of the single nanoring structure of Figure 2;

3a is a schematic view showing a transmission state of a surface plasmon filter according to an embodiment of the present invention; FIG. 3b is a scanning electron micrograph of a single nanoring structure in an embodiment of the present invention; and FIG. 4 is a surface plasmon filter according to an embodiment of the present invention. Schematic diagram of the working principle of the optical device; Figure 5a is a schematic view of a nano-ring structure array having different outer diameter and inner diameter difference, dividing a white light into monochromatic light;

Figure 5b is an electric field intensity distribution diagram of the surface (upper row) and inner (lower row) of the nanoring structure obtained by simulation of the finite time domain difference method;

Figure 6a is an atomic force micrograph of an array of nanoring structures in an embodiment of the present invention;

6b is a perspective view of a scanning electron microscope of an array of nano-rings in an embodiment of the present invention; FIG. 7 is a difference in the composition of the "NEU" using a nano-ring structure, which is different under the illumination of white light. FIG. 8 is a nano-circle in the embodiment of the present invention. The ring structure array filters a bundle of broadband white light sources into monochromatic light.

In the figure: 11 : base material; 21 : metal film; 22: nano slit; 23: groove antenna; 24: layer stack linear grating; 31 : annular hollow structure; 41 : white light source; 42: set and analysis Device. detailed description

The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings and embodiments. The following examples are merely illustrative of the invention, but are not intended to limit the scope of the invention.

Embodiment 1

In order to solve the problem of polarization sensitivity existing in the slot antenna and the layer stack linear grating filter of the prior art, a surface plasmon filter is provided in this embodiment; as shown in FIG. 2a-2c As shown, the surface plasmon filter mainly includes a base material 11 and a metal film 21 attached to the base material 11; the metal film 21 is provided with a plurality of annular hollow structures 31 (ie, a nano ring structure) The difference between the outer diameter and the inner diameter of each of the annular hollow structures 31 is related to the wavelength of the monochromatic light selectively transmitted by the surface plasmon filter; since the annular hollow structure 31 is highly symmetrical, the circle The annular hollow structure 31 is still applicable to unpolarized light (such as natural light), thereby solving the polarization sensitivity problem common to both four-slot antennas and layer-stack linear grating filters, making the application of filter-like devices wider. , more suitable for non-polarized natural light. The base material 11 in this embodiment may be quartz, glass or other transparent material; The metal film 21 may be made of any one of metals such as gold, silver, a platinum group metal or an aluminum group metal; in actual production, aluminum or gold is preferred.

The above nano ring structure also has another outstanding advantage, that is, a single nano ring structure also has a light splitting function; that is, only one nano ring structure can be used, by controlling the outer diameter and the inner diameter of the nano ring structure. By dividing the difference, a white light can be divided into monochromatic light; this is because the position of the plasmon resonance peak of the transmission type surface is modulated by controlling the difference between the outer diameter and the inner diameter of the nanoring structure. Rather than adjusting the period of the array of nanoring structures.

In practical applications, a plurality of nano ring structures are preferably disposed, and the plurality of nano ring structure arrays are arranged, because when only a single nano ring structure is provided, the transmission area is too small may cause relatively low. The transmission energy; and the plurality of nano-ring structures arranged in the array can enhance the overall transmission effect of the surface plasmon filter, and the light intensity distribution of the emitted light is relatively uniform.

The surface plasmon filter provided by the present invention can be used for various purposes; for example, when the nano ring structure in the filter is embedded in a surface plasmon type solar cell, the polarization state of the nano ring structure to the incident light Insensitivity can allow more energy to be captured during the photoelectric conversion process, thereby greatly increasing the photoelectric conversion efficiency of the solar cell. In addition, since the spectroscopic mechanism of the nano-ring structure is different from the groove antenna of the periodic structure and the layered linear grating, a single nano-ring structure can have a filtering effect, so the filter can realize ultra-small pixels (less than 1). Micron), therefore, provides powerful technical support for maximizing resolution in displays of the same shape and size.

The invention also provides a method for preparing any of the above surface plasmon filters; the preparation method of the surface plasmon filter mainly comprises the following steps:

Step 1: forming a metal film on the base material; the base material in this embodiment may be quartz, glass or other transparent material; the metal film may be made of any one of metal such as gold, silver or aluminum;

Step 2: forming a plurality of annular hollow structures on the metal film; for example:

Using a focused ion etching method, a plurality of annular hollow structures are formed on the metal film; the focused ion beam etching method is irreplaceable compared to other methods of forming an annular hollow structure. The advantages. For example, compared to electrons and solids, ions have less scattering effect in solids and can etch at less than 50 nanometers at faster write speeds. Therefore, focused ion beam etching is an ideal for nanofabrication. method. In addition, another advantage of the focused ion beam etching method is that maskless implantation can be performed under the control of a computer, or even a development-free etching can be performed, thereby directly fabricating various nano device structures.

Moreover, when the focused ion beam etching process is used, the sidewall of the surface plasmon filter can be perpendicularized by rotating the etching table to a certain angle. The oblique view of the scanning electron microscope shown in Fig. 6b shows that the nanoring structure prepared in this embodiment has a relatively uniform sidewall and a relatively smooth device surface, and the atomic force micrograph shown in Fig. 6a. The surface of the nanoring structure shown is consistent. More importantly, the focused ion beam etching method has great freedom to fabricate nanodevices of almost any shape and type. As shown in FIG. 7 , the word "NEU" (Northeastern University) composed of a nano ring structure is used; FIG. 8 shows that the nano ring structure array in the embodiment of the present invention filters a bundle of broadband white light sources into monochromatic light. In addition, focused ion beam etching can also be used to fabricate a variety of devices such as nanopillars, nanotips, and nanoarms, making it possible to produce more nanometer-scale optical and electronic devices.

Based on the above-mentioned nano-ring structure, the theoretical simulation and calculation are firstly taken by the finite-time difference method to specify the direction for the preparation and testing of the experimental surface plasmon filter, and the optimal parameter design is realized. Then, the designed surface plasmon filter is prepared experimentally, and the surface plasmon filter is tested and analyzed. The research process in this embodiment is complete and sufficient, and the prepared preparation method is easy to implement. The cost is very low, and the test method is perfect, which can complete the comprehensive analysis and evaluation of the surface plasmon filter.

As shown in FIG. 3a, in the embodiment, the surface plasmon filter operates in a transmissive state, and when a ray emitted from the illuminating light source 41 is incident from the substrate direction to the surface of the device, the other side of the device is realized. The light is split, and a collection and analysis device 42 is provided on the side to collect and analyze the transmitted optical signal.

Scanning electron microscope for the prepared surface plasmon filter as shown in Figure 3b Since each of the individual nano ring structures in the array of nano ring structures has the function of splitting light, the surface plasmon filter in this embodiment can realize ultra-small pixels; specifically, the nanometer in FIG. 3b The outer diameter of the ring structure is 450 nanometers and the inner diameter is 400 nanometers, which enables splitting in a size range of less than 1 micron (at the same time, Apple's iPhone4 has a pixel size of only 78 microns).

The working principle of the surface plasmon filter in this embodiment is shown in FIG. 4: that is, using a fixed nano-ring structure array period, and only changing the difference between the outer diameter and the inner diameter of the nano-ring structure to adjust the transmission type resonance and At the same time, by controlling the period of the nano-ring structure array, it is large enough to make the planar formant in the near-infrared band to avoid interference with the transmission-type resonance mode in the visible light band, and finally prepare A surface plasmon filter is emitted. For example, in the experiment, a coaxial nano-ring structure with a fixed period of 1200 nm and a difference between the outer diameter and the inner diameter in the range of 10 nm to 160 nm can be used to divide a broadband white light source into different Monochromatic light of color; It is apparent from Fig. 4 that the nanoring structure has a significant enhancement in the electric field distribution at the surface when resonance occurs (760 nm) compared to when resonance does not occur (640 nm).

When the inner diameter is fixed and only the outer diameter is changed, thereby adjusting the difference between the outer diameter and the inner diameter of the nano ring structure to form a different array of nano ring structures, a broadband white light source can be filtered into a monochromatic light. , as shown in Figure 5a. In addition, through the calculation method of finite time domain difference, the field strength distribution map of the ring surface and its internal space can be simulated and simulated in the case of resonance occurrence and non-occurrence; as shown in Figure 5b, it can be seen that When the resonance occurs (the left column), the maximum field strength is effectively increased by about 50 times than when the resonance does not occur (the right column); at the same time, it can be seen from the top view (upper row) or the cross-sectional view (lower row). The energy of the light can be well confined in the nano-ring structure region, that is to say, the surface plasmon filter provided by the embodiment has little loss and relatively high transmission efficiency.

In summary, the present invention can improve the spectroscopic effect of the surface plasmon filter and maximize the performance and transmission efficiency of the surface plasmon filter; and solve the existence of other types of existing filter devices in the prior art. Polarization sensitivity issues and the inability to maximize transmission Problem. The surface plasmon filter provided by the invention can be widely applied in the fields of imaging, display and filtering, and has great advantages such as good compatibility and high resolution of the surface plasmon filter, so it has a very broad development. Space and great development potential. In addition, since the surface plasmon filter uses precious metals as a raw material, the final structure is very stable and has an extremely long service life; especially when gold (Au) is used as a very stable and non-oxidizable material. The surface plasmon filter will always work as long as there is no artificial damage.

Further, the surface plasmon filter provided by the present invention mainly works in the visible light band; but only by changing the structural parameters of the surface plasmon filter (such as the outer diameter and the inner diameter difference of the nano ring structure, The array period and shape, etc. can be moved to the near-infrared band to prepare a near-infrared spectrum analyzer. Such a near-infrared spectrum analyzer has good performance and can accurately reproduce various saved data. advantage.

Finally, since the filter in the prior art is widely used in the fields of imaging and display, there is a great economic benefit; moreover, the surface plasmon filter of the present invention is compatible with the working principle of the existing liquid crystal display panel, Therefore, the surface plasmon filter is very useful in the field of display technology; for example, taking the iPhone 4 product of Apple Inc. as an example, the retina imaging technology (Retina) used is compared with the conventional display technology used in its early products. There is a big breakthrough, the entire screen has a very high pixel density (Pixels Per Inch, abbreviated as PPI), which compresses the resolution of 960 640 into a 3.5-inch display; for the nano-rings of the present invention In terms of structure, the minimum pixel can reach less than 1 micron, so the pixel density can be further significantly increased for the same size screen, so it can provide powerful technical support for maximizing resolution in the same shape and size of the display. .

The above embodiments are merely illustrative of the present invention and are not to be construed as limiting the scope of the invention, and various modifications and changes can be made without departing from the spirit and scope of the invention. Equivalent technical solutions are also within the scope of protection of the present invention. Industrial applicability

The surface plasmon filter provided by the embodiment of the invention is provided on the metal film A number of annular hollow structures, using the highly symmetrical nature of the annular hollow structure, solve the polarization sensitivity problems commonly found in four-slot antennas and layer-stack linear grating filters, making the application range of similar filter devices more Wide, more suitable for non-polarized natural light.

Claims

Rights request

1. A surface plasmon filter, characterized in that it includes: a base material and a metal film attached to the base material; a plurality of annular hollow structures are provided on the metal film.

2. The surface plasmon filter according to claim 1, wherein the number of the annular hollow structure is one.

3. The surface plasmon filter according to claim 1, wherein the number of the annular hollow structures is multiple, and the plurality of annular hollow structures are arranged in an array.

4. The surface plasmon filter according to any one of claims 1 to 3, characterized in that the difference between the outer diameter and the inner diameter of each annular hollow structure is equal to the difference between the surface plasmon filter and the surface plasmon filter. The choice of transmitted monochromatic light depends on the wavelength.

5. The surface plasmon filter according to claim 4, wherein the difference between the outer diameter and the inner diameter of each of the annular hollow structures is not less than 10 nanometers and not more than 160 nanometers.

6. The surface plasmon filter according to claim 4, wherein the planar resonance peak of the surface plasmon filter is located in the near-infrared band.

7. The surface plasmon filter according to any one of claims 1-3 or 5-6, characterized in that the metal film is made of gold, silver, platinum group metal or aluminum group metal.

8. The surface plasmon filter according to claim 7, wherein the base material is quartz or glass.

9. A method for preparing a surface plasmon filter, which is characterized by including: Step 1: forming a metal film on the base material;

Step 2: Form several annular hollow structures on the metal film.

10. The surface plasmon filter preparation method according to claim 9, wherein the step 2 further includes:

Using a focused ion etching method, several annular hollow structures are formed on the metal film.