Single narrow-pass two-dimensional closed surface wave photonic crystal structure

Abstract

The present invention provides a single narrow-pass two-dimensional closed surface wave photonic crystal structure, which is formed by a first metal plate, surrounding metal columns, a defective metal column and the interval between the defective metal column and the first metal plate to form a surface wave photonic crystal structure, and a second metal plate to form a closed surface wave photonic crystal structure, thereby improving the anti-interference ability of the photonic crystal; in addition, by arranging the surrounding metal columns in rows and columns with equal spacing; arranging the defective metal columns in columns, or arranging the defective metal columns in an L-shape with connected rows and columns; the defective metal columns are adjacent to the surrounding metal columns on both sides, and the interval between the two defective metal columns is twice the interval between the two adjacent surrounding metal columns; the interval between the defective metal column and the adjacent surrounding metal columns is equal to the interval between the two adjacent surrounding metal columns arranged in rows and columns with equal spacing, the problem of in-band oscillation of the two-dimensional closed surface wave photonic crystal structure can be solved, and the bandwidth and in-band frequency oscillation of the photonic crystal structure can be reduced.

Description

Technical Field

[0001] The invention belongs to the field of integrated optics, and in particular relates to a single narrow-pass two-dimensional closed surface wave photonic crystal structure. Background Art

[0002] In 1969, Dr. Miller of Bell Labs proposed the concept of integrated optics. Similar to integrated circuits, the primary research goal of integrated optics is to integrate large, bulky free-space optical systems onto a single substrate. The size of integrated optical devices varies with frequency band, primarily at the millimeter level in the GHz band and the micrometer level in the THz band. They also offer low power consumption and a compact size. Furthermore, since the integrated devices are housed in a closed environment, they are minimally susceptible to external interference.

[0003] At a time when integrated circuits are constrained by Moore's Law and have limited prospects, optoelectronics technology has shown great advantages: the speed of photons in integrated optical circuits is much greater than the speed of electrons in integrated circuits, and it has a greater information capacity.

[0004] In recent decades, with the rapid development of integrated optical circuit technology, photonic crystals, also known as "optical semiconductors," have attracted widespread attention. Photonic crystals are a new type of optical microstructure material whose dielectric constant varies periodically with space. They can be categorized into three main types based on their periodicity in three dimensions: one-dimensional, two-dimensional, and three-dimensional. Two-dimensional photonic crystals can be further subdivided into porous planar photonic crystals, dielectric pillar photonic crystals, and the currently cutting-edge quasi-photonic crystals, based on their structural properties. Photonic crystals possess two key characteristics: a photonic bandgap and photon localization. The most fundamental characteristic is the photonic bandgap.

[0005] In nature, surface plasmons are collective oscillation modes of free electrons and photons formed by the interaction of electromagnetic waves with free electrons on the surface of metals. Surface plasmons can only exist at the interface of materials with opposite signs of the real parts of their dielectric constants, such as the interface between metal and air. Surface plasmons can be divided into two types: surface plasmon polaritons that propagate at the interface between metal and dielectric, and localized surface plasmons that are confined to the surface of metal nanoparticles. In 2004, JBPentry et al., in order to realize surface plasmon polaritons in the microwave and millimeter wave bands, etched periodically arranged air holes in a metal cube to achieve surface plasmon polariton (SPP) transmission in the microwave and millimeter wave bands. This structure is called an artificial surface plasmon (SSPP). In 2005, Hibbins et al. from the University of Exeter published their experimental results on SSPP in Science, sparking a surge of research on the topic. That same year, Bing Wang et al. from Wuhan University introduced periodicity into a metal-insulator-metal structure to create a plasmon band gap. In 2016, Zhen Gao et al. combined artificial surface plasmons with photonic crystals, proposing a novel metallic photonic crystal—a two-dimensional surface wave photonic crystal. However, this structure was susceptible to interference from external factors, and the photonic crystal exhibited a wide bandwidth and severe intra-band oscillations. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a single narrow-pass two-dimensional closed surface wave photonic crystal structure to solve the problems in the prior art of metal photonic crystals - two-dimensional surface wave photonic crystals, which are highly susceptible to interference from external factors, and have wide bandwidth and severe in-band oscillations.

[0007] To achieve the above-mentioned and other related objectives, the present invention provides a single narrow-pass two-dimensional closed surface wave photonic crystal structure, the photonic crystal structure comprising:

[0008] A first metal plate, a metal pillar array, and a second metal plate stacked in sequence;

[0009] The metal pillar array includes surrounding metal pillars and defective metal pillars; the two ends of the surrounding metal pillars are in contact with the first metal plate and the second metal plate respectively; the surrounding metal pillars are arranged in rows and columns with equal spacing; the defective metal pillars are arranged in columns, or the defective metal pillars are arranged in an L-shape with connected rows and columns; both sides of the defective metal pillar are adjacent to the surrounding metal pillars, and the spacing between two adjacent defective metal pillars is twice the spacing between two adjacent surrounding metal pillars; the spacing between the defective metal pillar and the adjacent surrounding metal pillars is equal to the spacing between two adjacent surrounding metal pillars arranged in rows and columns with equal spacing;

[0010] The height of the defective metal pillar is smaller than that of the surrounding metal pillars, and the cross-sectional area of the defective metal pillar is smaller than that of the surrounding metal pillars.

[0011] Optionally, the metal column array is a square array.

[0012] Furthermore, the cross-sectional shape of the surrounding metal pillars is the same as the cross-sectional shape of the defective metal pillar, and both are four-fold symmetrical figures.

[0013] Furthermore, the four-fold symmetrical figure is a square, a rhombus or a circle.

[0014] Furthermore, the four-fold symmetrical figure is a square, the height of the surrounding metal column is 0.5 mm, the spacing between two adjacent surrounding metal columns is 0.5 mm, the side length of the surrounding metal column is 0.25 mm, the height of the defective metal column is 0.45 mm, and the side length of the defective metal column is 0.1 mm.

[0015] Optionally, the defective metal pillars are arranged in an L-shape with connected rows and columns, and the expanded length of the L-shape is equal to the length of the metal pillar array.

[0016] Optionally, the defective metal pillars are arranged in columns, and the metal pillar array includes more than one column of the defective metal pillars.

[0017] Optionally, the defective metal pillars are arranged in an L-shape with connected rows and columns, and the metal pillar array includes more than one L-shaped defective metal pillars.

[0018] Optionally, the first metal plate, the second metal plate and the metal column array are made of the same material, wherein the material includes one of gold metal, silver metal, copper metal and aluminum metal.

[0019] As described above, the single narrow-pass two-dimensional closed surface wave photonic crystal structure of the present invention forms a surface wave photonic crystal structure through the first metal plate, the surrounding metal columns, the defective metal columns and the gap between the defective metal columns and the first metal plate, and forms a closed surface wave photonic crystal structure through the second metal plate, thereby improving the anti-interference ability of the existing metal photonic crystal - the two-dimensional surface wave photonic crystal; in addition, by arranging the surrounding metal columns in rows and columns with equal spacing; the defective metal columns are arranged in columns, or the defective metal columns are arranged in an L-shape with connected rows and columns; the defective metal columns are adjacent to the surrounding metal columns on both sides, and the gap between the two adjacent defective metal columns is twice the gap between the two adjacent surrounding metal columns; the gap between the defective metal column and the adjacent surrounding metal columns is equal to the gap between the two adjacent surrounding metal columns arranged in rows and columns with equal spacing, which can solve the problem of in-band oscillation of the two-dimensional closed surface wave photonic crystal structure, form a single narrow-pass filter structure, and reduce the bandwidth and in-band frequency oscillation of the photonic crystal structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Shown is a schematic planar structural diagram of a metal pillar array in a single narrow-pass two-dimensional closed surface wave photonic crystal structure according to an example of the present invention.

[0021] Figure 2 A schematic planar structural diagram of a metal pillar array in a single narrow-pass two-dimensional closed surface wave photonic crystal structure according to another example of the present invention is shown.

[0022] Figure 3 Display as Figure 1 Schematic cross-sectional view of a single narrow-pass two-dimensional closed surface wave photonic crystal structure in the BB' direction.

[0023] Figure 4 Display as Figure 1 Schematic diagram of the cross section of a single narrow-pass two-dimensional closed surface wave photonic crystal structure in the AA' direction.

[0024] Figure 5 The figure shows a normalized transmission curve of an exemplary two-dimensional closed surface wave photonic crystal structure, wherein the abscissa is the operating frequency and the ordinate is the normalized transmission constant.

[0025] Figure 6 The figure shows a normalized transmission curve of a two-dimensional closed surface wave photonic crystal structure of a specific example, wherein the abscissa is the operating frequency and the ordinate is the normalized transmission coefficient.

[0026] Figure 7 Another specific example is shown with Figure 6Normalized transmission curve of the two-dimensional closed surface wave photonic crystal structure, where the horizontal axis is the operating frequency and the vertical axis is the normalized transmission coefficient.

[0027] Component number description

[0028] 10 First Metal Plate

[0029] 11 Second metal plate

[0030] 12 Metal Pillar Array

[0031] 121 surrounding metal columns

[0032] 122 Defective Metal Column DETAILED DESCRIPTION

[0033] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0034] See also Figures 1 to 7 It should be noted that the diagrams provided in this embodiment are merely schematic illustrations of the basic concept of the present invention. Therefore, the diagrams only show components relevant to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be changed according to actual needs, and the component layout may also be more complex.

[0035] like Figures 1 to 4 As shown, this embodiment provides a single narrow-pass two-dimensional closed surface wave photonic crystal structure, the photonic crystal structure comprising:

[0036] like Figure 3 and Figure 4 As shown, a first metal plate 10, a metal pillar array 12 and a second metal plate 11 are stacked in sequence;

[0037] The metal pillar array 12 includes surrounding metal pillars 121 and defective metal pillars 122 (such as Figure 1 and Figure 2 The two ends of the surrounding metal column 121 are in contact with the first metal plate 10 and the second metal plate 11 (as shown); Figure 3 The surrounding metal pillars 121 are arranged in rows and columns with equal spacing (as shown); Figure 1 and Figure 2 The defective metal pillars 122 are arranged in rows (as shown); Figure 1As shown), or the defective metal pillars 122 are arranged in an L-shaped manner in connected rows and columns (as shown Figure 2 Both sides of the defective metal column 122 are adjacent to the surrounding metal columns 121 (as shown); Figure 1 and Figure 2 As shown), the interval L2 between two adjacent defective metal pillars is twice the interval L3 between two adjacent surrounding metal pillars; the interval L4 between the defective metal pillar 122 and the adjacent surrounding metal pillars 121 is equal to the interval L3 between two adjacent surrounding metal pillars 121 arranged in rows and columns with equal spacing;

[0038] A height h2 of the defective metal pillar 122 is smaller than a height h1 of the surrounding metal pillars 121 . A cross-sectional area of the defective metal pillar 122 is smaller than a cross-sectional area of the surrounding metal pillars 121 .

[0039] It should be noted that the definition of rows and columns in this embodiment is based on the transmission direction of light along a certain straight line in the photonic crystal structure. Figure 1 , the direction of light transmission in the photonic crystal structure is defined as the column direction, that is, the AAˊ direction, and the direction perpendicular to the light transmission direction is the row direction, that is, the BBˊ direction; then Figure 2 In the photonic crystal structure, if the light is transmitted along the left and right straight lines as a row, then the light is transmitted along the up and down straight lines as a row; if the light is transmitted along the up and down straight lines as a row, then the light is transmitted along the left and right straight lines as a row.

[0040] In this embodiment, a surface wave photonic crystal structure is formed by the first metal plate 10, the surrounding metal columns 121, the defective metal columns 122 and the gap between the defective metal columns 122 and the first metal plate 10, and a closed surface wave photonic crystal structure is formed by the second metal plate 11, thereby improving the anti-interference ability of the existing metal photonic crystal - the two-dimensional surface wave photonic crystal; in addition, by arranging the surrounding metal columns in rows and columns with equal spacing; the defective metal columns are arranged in columns, or the defective metal columns are arranged in an L-shape with connected rows and columns; both sides of the defective metal column are adjacent to the surrounding metal columns, and the gap between two adjacent defective metal columns is twice the gap between two adjacent surrounding metal columns; the gap between the defective metal column and the adjacent surrounding metal columns is equal to the gap between two adjacent surrounding metal columns arranged in rows and columns with equal spacing, the problem of in-band oscillation of the two-dimensional closed surface wave photonic crystal structure can be solved, a single narrow-pass filter structure is formed, and the bandwidth and in-band frequency oscillation of the photonic crystal structure are reduced.

[0041] As an example, the metal pillar array 12 is selected to be a square array, but it is not limited thereto, and other array structures suitable for this embodiment are also acceptable.

[0042] As an example, all of the surrounding metal pillars 121 in the metal pillar array 12 are identical, and all of the defective metal pillars 122 in the metal pillar array 12 are also identical. Preferably, the cross-sectional shape of the surrounding metal pillars 121 is the same as the cross-sectional shape of the defective metal pillars 122, and both are four-fold symmetrical figures, such as squares, diamonds, or circles. The so-called four-fold symmetrical figure means that the figure has four axes of symmetry, which are respectively in the four directions of 0°, 45°, 90°, and 135°. Selecting a four-fold symmetrical figure can keep each defective metal pillar 122 is isotropic in the four directions, so that the coupling of electromagnetic waves between adjacent defective metal pillars 122 is equivalent, even at the L-shaped corners. This is the same, so that the L-shaped defective metal pillars 122 can effectively reduce or even avoid light loss at the corners.

[0043] Such as 1 and Figure 2 As shown, as an example, the defective metal pillars 122 are arranged in an L-shape with connected rows and columns (eg Figure 2 As shown), the expanded length of the L-shaped metal pillar array 12 is equal to the length L1, that is, when the L-shaped defective metal pillar 122 is straightened into a straight line, its length is equal to Figure 1 The length of the linear defective metal pillars 122 is the same as that of the linear defective metal pillars 122. However, this is not limited thereto, and the L-shaped extended length can also be smaller than or greater than the length L1 of the metal pillar array 12.

[0044] like Figure 1 As shown, as an example, when the defective metal pillars 122 are arranged in columns, the metal pillar array 12 includes more than one column of the defective metal pillars 122, that is, when it includes one column of the defective metal pillars 122, it forms a linear single narrow-pass filter, and when it includes more than two columns of the defective metal pillars 122, it forms more than two linear single narrow-pass filters.

[0045] like Figure 2 As shown, as an example, when the defective metal pillars 122 are arranged in an L-shape with connected rows and columns, the metal pillar array 12 includes more than one L-shaped defective metal pillars 122, that is, when one L-shaped defective metal pillar 122 is included, an L-shaped single narrow-pass filter is formed, and when two or more L-shaped defective metal pillars 122 are included, two or more L-shaped single narrow-pass filters are formed.

[0046] As an example, the first metal plate 10, the second metal plate 11 and the metal column array 12 are made of the same material, wherein the material may include one of gold metal, silver metal, copper metal and aluminum metal. The specific material can be selected according to needs and is not overly restricted here.

[0047] The design of the single narrow-pass two-dimensional closed surface wave photonic crystal structure of this embodiment is introduced below in conjunction with specific experimental examples, but this should not be used as a limitation to the scope of the present invention. In practice, changes in the operating frequency band, dispersion curve and other results caused by changing any geometric parameters fall within the scope of the present invention.

[0048] like Figure 1 and Figure 3 As shown, a single narrow-pass two-dimensional closed surface wave photonic crystal structure is provided, including an upper first metal plate 10, an intermediate metal column array 12 and a lower second metal plate 11. The intermediate metal column array 12 is a two-dimensional periodic metal square column, that is, the cross-sectional shapes of the surrounding metal columns 121 and the defective metal columns 122 are all square, and the materials used in the three-layer structure are all metals commonly used in waveguides. If operating in the 0.1THZ frequency band, based on A. Yariv's Coupled-Resonator Optical Waveguide (CROW) theory, the metal pillar array 12 is formed as follows: the height h1 of the surrounding metal pillars 121 is selected to be 0.5mm, the side length d1 of the surrounding metal pillars 121 is selected to be 0.25mm, and the interval L3 between two adjacent surrounding metal pillars 121 is selected to be 0.5mm. It should be pointed out here that the interval here and the interval mentioned subsequently refer to the distance between the center positions of the two objects, thereby forming a two-dimensional square array with a unit side length of 0.5mm, and then one column in the two-dimensional square array is replaced with a defective metal pillar 122, and the defective metal pillars 122 are arranged in an A0A0... manner, that is, the interval L2 between two adjacent defective metal pillars 122 is set to be 1.0mm, the height of the defective metal pillar 122 is set to be 0.45mm, and the side length d2 of the defective metal pillar 122 is set to be 0.1mm.

[0049] Figure 5 A row of surrounding metal pillars 121 is directly replaced by a row of defective metal pillars 122, and the defective metal pillars 122 are not arranged in an interval manner, that is, in an AAAA... manner to form a metal pillar array 12. The normalized transmission coefficient curve of the filter is obtained while other parameters remain unchanged. The operating frequency range is 90.5GHz to 119.6GHz, with high transmission efficiency and strong noise resistance, but the in-band oscillation is relatively serious.

[0050] Figure 6 To adopt Figure 1 The normalized transmission coefficient curve of the filter formed by the metal column array 12 has an operating center frequency of 102.6 GHz and a half-height width corresponding to a frequency of 101.7 GHz to 104.9 GHz. Figure 5 The bandwidth is only 3.12%, which effectively solves the problem of severe in-band oscillation and wide bandwidth of the filter.

[0051] Figure 7 To adopt Figure 1 The parameters of the metal pillar array 12 are the same as those of the metal pillar array 12, but the linear column defect metal pillars 122 are set to be L-shaped connected row and column defect metal pillars 122, and the extended length of the L-shaped defect metal pillars 122 is the same as that of the metal pillar array 12. Figure 1 The lengths of the linear defective metal pillars 122 are the same. A comparison of the normalized transmission coefficient curves for filters formed by linear and L-shaped defective metal pillars 122 is shown. The solid line represents the normalized transmission coefficient curve for the linear single narrow-pass filter, while the dashed line represents the normalized transmission coefficient curve for the L-shaped single narrow-pass filter. It can be seen that there is almost no light loss after the 90° right-angle bend. Therefore, the method in this experimental example is applicable to both linear and L-shaped scenarios.

[0052] In summary, the present invention provides a single narrow-pass two-dimensional closed surface wave photonic crystal structure, which is formed by the first metal plate, the surrounding metal columns, the defective metal columns and the gap between the defective metal columns and the first metal plate to form a surface wave photonic crystal structure, and the second metal plate to form a closed surface wave photonic crystal structure, thereby improving the anti-interference ability of the existing metal photonic crystal - the two-dimensional surface wave photonic crystal; in addition, by arranging the surrounding metal columns in rows and columns with equal spacing; the defective metal columns are arranged in columns, or the defective metal columns are arranged in an L-shape with connected rows and columns; the defective metal columns are adjacent to the surrounding metal columns on both sides, and the gap between the two adjacent defective metal columns is twice the gap between the two adjacent surrounding metal columns; the gap between the defective metal column and the adjacent surrounding metal columns is equal to the gap between the two adjacent surrounding metal columns arranged in rows and columns with equal spacing, which can solve the problem of in-band oscillation of the two-dimensional closed surface wave photonic crystal structure, form a single narrow-pass filter structure, and reduce the bandwidth and in-band frequency oscillation of the photonic crystal structure. Therefore, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0053] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A single narrow-pass two-dimensional closed surface wave photonic crystal structure, characterized in that: The photonic crystal structure comprises: A first metal plate, a metal pillar array, and a second metal plate stacked in sequence; The metal pillar array includes surrounding metal pillars and defective metal pillars; the two ends of the surrounding metal pillars are in contact with the first metal plate and the second metal plate respectively; the surrounding metal pillars are arranged in rows and columns with equal spacing; the defective metal pillars are arranged in columns, or the defective metal pillars are arranged in an L-shape with connected rows and columns; both sides of the defective metal pillar are adjacent to the surrounding metal pillars, and the spacing between two adjacent defective metal pillars is twice the spacing between two adjacent surrounding metal pillars; the spacing between the defective metal pillar and the adjacent surrounding metal pillars is equal to the spacing between two adjacent surrounding metal pillars arranged in rows and columns with equal spacing; The height of the defective metal column is smaller than the height of the surrounding metal columns, and the cross-sectional area of the defective metal column is smaller than the cross-sectional area of the surrounding metal columns; All of the surrounding metal pillars in the metal pillar array are identical, and all of the defective metal pillars in the metal pillar array are also identical.

2. The single narrow-pass two-dimensional closed surface wave photonic crystal structure according to claim 1, characterized in that: The metal column array is a square array.

3. The single narrow-pass two-dimensional closed surface wave photonic crystal structure according to claim 2, characterized in that: The cross-sectional shape of the surrounding metal pillars is the same as the cross-sectional shape of the defective metal pillars, and both are four-fold symmetrical figures.

4. The single narrow-pass two-dimensional closed surface wave photonic crystal structure according to claim 3, characterized in that: The four-fold symmetrical figure is a square, a rhombus or a circle.

5. The single narrow-pass two-dimensional closed surface wave photonic crystal structure according to claim 4, characterized in that: The four-fold symmetrical figure is a square, the height of the surrounding metal column is 0.5 mm, the spacing between two adjacent surrounding metal columns is 0.5 mm, the side length of the surrounding metal column is 0.25 mm, the height of the defective metal column is 0.45 mm, and the side length of the defective metal column is 0.1 mm.

6. The single narrow-pass two-dimensional closed surface wave photonic crystal structure according to claim 2, characterized in that: The defective metal pillars are arranged in an L-shape with connected rows and columns, and the expanded length of the L-shape is equal to the length of the metal pillar array.

7. The single narrow-pass two-dimensional closed surface wave photonic crystal structure according to claim 1, characterized in that: The defective metal pillars are arranged in columns, and the metal pillar array includes more than one column of the defective metal pillars.

8. The single narrow-pass two-dimensional closed surface wave photonic crystal structure according to claim 1, characterized in that: The defective metal pillars are arranged in an L-shape with connected rows and columns, and the metal pillar array includes more than one L-shaped defective metal pillars.

9. The single narrow-pass two-dimensional closed surface wave photonic crystal structure according to claim 1, characterized in that: The first metal plate, the second metal plate and the metal column array are made of the same material, wherein the material includes one of gold metal, silver metal, copper metal and aluminum metal.

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