A two-dimensional pitch-line photonic-crystal-based boundary-mode conical concentrator

Abstract

The application relates to a boundary mode conical concentrator based on a two-dimensional nodal line photonic crystal, which comprises a photonic crystal conical concentration area, a waveguide channel, an electromagnetic wave input port and an output port. The conical concentrator is composed of photonic crystals with different rotating degrees. The width of the photonic crystal structure is gradually narrowed by modulation, so that the transmission channel of the concentrator is conical, thereby achieving the concentration effect of electromagnetic waves. The boundary mode conical concentrator designed based on the two-dimensional nodal line photonic crystal makes the coupling effect of the bulk state of the conical concentration area and the interface state in the waveguide channel, and better mutual matching. The application can modulate the size of some waveguide modes, and is beneficial to efficiently connecting one or more photonic devices with different sizes.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photonics and integrated devices, in particular to a kind of boundary mode conical concentrator based on two-dimensional nodal line photonic crystal. BACKGROUND

[0002] The 21st century is called information age, and optics has significant advantages in many application fields of information technology, including high density, digitization and high speed of processing. With the progress of the times and the change of technology, higher requirements are put forward for information processing and transmission devices. Mode mismatch is one of the problems commonly existing in the field of optics. This mode coupling is usually used in optical systems to improve the coupling efficiency between large light sources and certain small samples. It is a key component of hybrid photonic integrated systems. Due to the size difference, there are certain difficulties in mode coupling for traditional photonic devices, and they are limited by electromagnetic wave transmission channels, and a large amount of reflection will be generated when coupling, thereby reducing the transmission efficiency. SUMMARY

[0003] In view of the problems existing in the prior art, the present application provides a kind of boundary mode conical concentrator based on two-dimensional nodal line photonic crystal, which can reduce the limitation of electromagnetic wave transmission channel and effectively improve the transmission efficiency.

[0004] In order to achieve the above purpose, the present application provides a kind of boundary mode conical concentrator based on two-dimensional nodal line photonic crystal, which includes photonic crystal conical concentration area and waveguide channel, photonic crystal conical concentration area and waveguide channel are connected from left to right by photonic crystal structure I, II, III, IV and photonic crystal structure V to form a conical concentrator;The photonic crystal structure of photonic crystal conical concentration area and waveguide channel is composed of A1, A2, A3, A4, A5, B1, B2, B3, B4, B5 and O overlap arrangement;The photonic crystal is composed of shell structure arranged according to hexagonal lattice, and the lattice constant a of the hexagonal lattice is 25mm;There is a shell structure in the unit cell o of the photonic crystal, which is divided into three equal parts by digging out three rectangular areas, wherein the rectangular width w is adjustable, the dielectric column in the shell structure is composed of alumina dielectric material, the relative dielectric constant is 9.5, the background material is air, the relative dielectric constant is 1, the inner radius of the dielectric column is R1=7.5mm, the outer radius is R2=10.5mm, the height is d=10mm, and the parameters of the photonic crystal can be freely adjusted according to the actual working frequency of the concentrator;

[0005] The medium column s at the bottom of the photonic crystal primitive cell o is moved to the right by distances of dcl=0.08a, dc2=0.1a, dc3=0.12a, dc4=0.14a, and dc5=0.16a, respectively, and the moved s is taken as the basis, and the primitive cell center is taken as the origin to rotate by 120° counterclockwise and 120° clockwise, respectively, to obtain photonic crystals a1, a2, a3, a4, and a5, respectively; the movement of s to the right is taken as the positive direction;

[0006] The medium column s at the bottom of the photonic crystal primitive cell o is moved to the left by distances of dcl=0.08a, dc2=0.1a, dc3=0.12a, dc4=0.14a, and dc5=0.16a, respectively, and the moved s is taken as the basis, and the primitive cell center is taken as the origin to rotate by 120° counterclockwise and 120° clockwise, respectively, to obtain photonic crystals b1, b2, b3, b4, and b5, respectively; the movement of s to the left is taken as the negative direction;

[0007] The waveguide channel is formed by region V.

[0008] In addition, the two-dimensional nodal line photonic crystal-based boundary mode cone concentrator according to the above-mentioned embodiment of the present application can further have the following additional technical features:

[0009] As a further improvement of the present application, the photonic crystal structure A1 is formed by the photonic crystal primitive cell a1, wherein the x direction contains 8 primitive cells; the y direction contains 3 primitive cells;

[0010] The photonic crystal structure A2 is formed by the photonic crystal a2, wherein the x direction contains 3 primitive cells; the y direction contains 4 primitive cells;

[0011] The photonic crystal structure A3 is formed by the photonic crystal a3, wherein the x direction contains 4 primitive cells; the y direction contains 5 primitive cells;

[0012] The photonic crystal structure A4 is formed by the photonic crystal a4, wherein the x direction contains 3 primitive cells; the y direction contains 6 primitive cells;

[0013] The photonic crystal structure A5 is formed by the photonic crystal a5, wherein the x direction contains 9 primitive cells; the y direction contains 7 primitive cells;

[0014] The photonic crystal structure B1 is formed by the photonic crystal primitive cell b1, wherein the x direction contains 8 primitive cells; the y direction contains 3 primitive cells;

[0015] The photonic crystal structure B2 is formed by the photonic crystal b2, wherein the x direction contains 3 primitive cells; the y direction contains 4 primitive cells;

[0016] The photonic crystal structure B3 is formed by the photonic crystal b3, wherein the x direction contains 4 primitive cells; the y direction contains 5 primitive cells;

[0017] The photonic crystal structure B4 is composed of a photonic crystal b4, wherein the x direction contains 3 unit cells; and the y direction contains 6 unit cells;

[0018] The photonic crystal structure B5 is composed of a photonic crystal b5, wherein the x direction contains 9 unit cells; and the y direction contains 7 unit cells;

[0019] The photonic crystal structures O1, O2, O3, O4 and O5 are composed of a photonic crystal unit cell o, and contain 8, 3, 4, 3 and 9 unit cells in the x direction, respectively; and contain 9, 7, 5, 3 and 1 unit cells in the y direction, respectively.

[0020] As a further improved scheme of the present application, the concentrator is composed of five regions, and the upper, middle and lower parts of region I are arranged in the order of photonic crystal structures A1, O and B1;

[0021] Region II of the concentrator is arranged in the order of photonic crystal structures A2, O and B2; region III of the concentrator is arranged in the order of photonic crystal structures A3, O and B3; region IV of the concentrator is arranged in the order of photonic crystal structures A4, O and B4; and region V of the concentrator is arranged in the order of photonic crystal structures A5, O and B5.

[0022] As a further improved scheme of the present application, the two sides of the tapered concentrator are respectively provided with an excitation source P1 and an exit port P2.

[0023] The excitation source P1 is located at the leftmost side of the tapered concentrator; and the exit port P2 is located at the rightmost side of the photonic crystal tapered concentrator.

[0024] As a further improved scheme of the present application, the concentration area of the boundary mode tapered concentrator is composed of region I, region II, region III and region IV, which are sequentially linked from left to right.

[0025] The present application has the following beneficial effects:

[0026] In view of the problems of mode mismatching and low coupling efficiency caused by size difference of traditional photonic devices, the present application designs a boundary mode tapered concentrator by using the transmission property of the boundary state mode. The designed structure can be used for coupling between photonic devices of different mode sizes by modulating the width of the photonic crystal tapered concentration area, thereby reducing the transmission loss and improving the coupling efficiency. The tapered concentrator in the present application has the excellent characteristics of low environmental requirement, high compatibility, low loss, high degree of freedom of manipulation and the like. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a schematic diagram of the overall structure of the embodiment of the present application.

[0028] Figure 2 The photonic crystal unit cell of the present invention and the energy band diagram after the unit cell is rotated;

[0029] Figure 3a is the projected energy band diagram of the photonic crystal structure I in the present invention;

[0030] Figure 3b is the projected energy band diagram of the photonic crystal structure III of the present invention;

[0031] Figure 3c is the projected energy band diagram of the photonic crystal structure V in the present invention;

[0032] Figure 4a This is the electric field distribution diagram after the left side of the conical concentrator is excited by the excitation source in the present invention;

[0033] Figure 4b For the present invention Figure 4a The normalized electric field intensity distribution diagram after integrating the electric field along the y direction at the positions of the four yellow dotted lines shown. DETAILED DESCRIPTION

[0034] The following describes a boundary mode tapered concentrator based on a two-dimensional nodal line photonic crystal according to the present invention with reference to the accompanying drawings.

[0035] like Figure 1 As shown, in a specific embodiment of the present invention, a photonic crystal boundary mode tapered concentrator is provided, comprising a photonic crystal tapered concentrating region and a waveguide channel;

[0036] The photonic crystal boundary mode conical concentrator includes an excitation source P1 and an output port P2;

[0037] The photonic crystal boundary mode conical concentrator further comprises a photonic crystal structure I, a photonic crystal structure II, a photonic crystal structure III, a photonic crystal structure IV and a photonic crystal structure V;

[0038] The photonic crystal structures I, II, III, IV, and V are sequentially connected to form a photonic crystal tapered concentration region and a waveguide channel;

[0039] The photonic crystal region I has eight unit cells in the x direction in the rectangular coordinate system; the photonic crystal region II has three unit cells in the x direction; the photonic crystal region III has four unit cells in the x direction; the photonic crystal region IV has three unit cells in the x direction; the photonic crystal region V has nine unit cells in the x direction; and the photonic crystal regions I, II, III, IV, and V have fifteen unit cells in the y direction.

[0040] The upper, middle and lower three parts of the photonic crystal region I are arranged in order of photonic crystal structures A1, O, B1; the region II is arranged in order of upper, middle and lower photonic crystal structures A2, O, B2; the region III is arranged in order of upper, middle and lower photonic crystal structures A3, O, B3; the region IV is arranged in order of upper, middle and lower photonic crystal structures A4, O, B4; and the region V is arranged in order of upper, middle and lower photonic crystal structures A5, O, B5.

[0041] The photonic crystal unit cells a1, a2, a3, a4, a5 and b1, b2, b3, b4, b5 are deformed from the photonic crystal unit cell o; the photonic crystal unit cell o is arranged in a hexagonal lattice by a shell structure, and the lattice constant a of the hexagonal lattice is 25 mm.

[0042] The inner radius of the shell structure dielectric column is R1 = 7.5 mm, the outer radius is R2 = 10.5 mm, and the height is d = 10 mm.

[0043] The bottom dielectric column s in the photonic crystal unit cell o is moved forward by a distance of dc = 0.08a, 0.1a, 0.12a, 0.14a, 0.16a, and is rotated by 120° counterclockwise and 120° clockwise with s as the basis and the cell center as the origin, respectively, to obtain photonic crystal unit cells a1, a2, a3, a4 and a5.

[0044] The bottom dielectric column s in the photonic crystal unit cell o is moved backward by a distance of dc = 0.08a, 0.1a, 0.12a, 0.14a, 0.16a, and is rotated by 120° counterclockwise and 120° clockwise with s as the basis and the cell center as the origin, respectively, to obtain photonic crystal unit cells b1, b2, b3, b4 and b5.

[0045] The excitation source is a Gaussian beam source, and the center of the leftmost shell structure dielectric column is taken as the coordinate origin, and the coordinates of the excitation source are

[0046]

[0047] The excitation source is located on the left side of structure O1.

[0048] Figure 1It is the whole structure schematic diagram of the embodiment of the present application. o is the photonic crystal primitive cell when the shell structure medium column does not rotate, the inner radius of the shell structure medium column is R1=7.5mm, the outer radius is R2=10.5mm, and the lattice constant is a=25mm; the medium column s at the bottom of the photonic crystal primitive cell o is moved by a distance of dc=0.08a in the positive direction, and based on s and taking the center of the primitive cell as the origin, it is rotated by 120° in the counterclockwise direction and 120° in the clockwise direction respectively, to obtain the photonic crystal primitive cell structure a1; the medium column s at the bottom of the photonic crystal primitive cell o is moved by a distance of dc=0.08a in the negative direction, and based on s and taking the center of the primitive cell as the origin, it is rotated by 120° in the counterclockwise direction and 120° in the clockwise direction respectively, to obtain the photonic crystal primitive cell structure b1; the upper, middle and lower three parts of the concentrator region I are arranged in the order of photonic crystal structures A1, O and B1 to form; the upper, middle and lower three parts of the concentrator region II are arranged in the order of photonic crystal structures A2, O and B2 to form; the upper, middle and lower three parts of the concentrator region III are arranged in the order of photonic crystal structures A3, O and B3 to form; the upper, middle and lower three parts of the concentrator region IV are arranged in the order of photonic crystal structures A4, O and B4 to form; the upper, middle and lower three parts of the concentrator region V are arranged in the order of photonic crystal structures A5, O and B5 to form; P1 represents the electromagnetic wave input port of the boundary mode conical concentrator, and P2 represents the electromagnetic wave output port of the boundary mode conical concentrator.

[0049] Figure 2 It represents the band diagram of the photonic crystal primitive cell o and the photonic crystal primitive cell a1. When the shell structure medium column is not rotated, two energy bands of the photonic crystal o are degenerate. When the shell structure medium column is moved and rotated, the degenerate Dirac point of the photonic crystal a1 is opened and a band gap is formed.

[0050] Figure 3a It is the projected band of the photonic crystal structure I, the horizontal coordinate represents the wave vector kx, and the vertical coordinate represents the frequency. It can be seen from the dispersion diagram that the electromagnetic wave propagates in a bulk state in the structure I. Figure 3b It is the projected band of the photonic crystal structure III, and the electromagnetic wave still propagates in a bulk state in the structure III. Figure 3c It is the projected band of the photonic crystal structure V, and two interface state dispersions appear at the common band gap. The electric field of the interface state has good localization.

[0051] Figure 4aThe figure is the electric field distribution diagram of the boundary mode cone concentrator of the application at a frequency of 8.877 GHz. When the electromagnetic wave is incident on the designed photonic crystal structure from the P1 port, the electromagnetic wave propagates in the bulk state in the photonic crystal structures I, II, III and IV, and propagates in the interface state in the photonic crystal structure V. The electromagnetic wave propagation range remains basically unchanged in region I, and the electromagnetic wave propagation range gradually narrows after entering regions II, III and IV, and then gradually couples to the photonic crystal region V. The photonic crystal structure I, the photonic crystal structure III and the photonic crystal structure V each have 8, 4 and 9 unit cells in the x direction, and 15 unit cells in the y direction. Figure 4b The figure is the normalized electric field intensity distribution diagram after the electric field is integrated along the y direction at the positions of the four yellow dashed lines. The abscissa represents the distance from the y-axis direction to the coordinate origin, and the ordinate represents the normalized electric field intensity. As the photonic crystal cone structure gradually narrows, the distribution width of the electric field also gradually decreases. At the same time, the intensity of the electric field reaches a maximum at the waveguide channel. This shows that the designed cone concentrator has a very good concentrating and converging effect on the electromagnetic wave.

[0052] The theoretical basis of the application is as follows:

[0053] 1. When the photonic crystal shell layer structure dielectric column does not rotate, that is, the dielectric column s at the bottom of the lattice does not move, the unit cell structure satisfies the C 3V symmetry, and at this time, the photonic crystal has a node ring. When the dielectric column s at the bottom of the photonic crystal o unit cell is moved forward by a distance of dc=0.08a, the mirror image symmetry of the photonic crystal unit cell is broken when s is taken as the basis and the center of the unit cell is taken as the origin and rotated by 120° counterclockwise and 120° clockwise, respectively. An effective interaction mass m proportional to the rotation degree is introduced into the effective Hamiltonian, which causes the degenerate node ring band to be opened.

[0054] 2. The photonic crystals A 1-5 and B 1-5 have opposite effective interaction masses, and two flat interface state dispersions will appear in the common band gap of the two, that is, a localized electric field will appear at the interface of the two. When the photonic crystal O with a mass term of zero is placed between the photonic crystals A 1-5 and B 1-5 , the two interface state dispersions will overlap. Based on the regulation of the distribution area of the boundary state, the application designs a photonic crystal cone concentrator.

[0055] The present invention provides a boundary mode conical concentrator. There are numerous methods and approaches for implementing this technical solution. The above is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. Components not specified in this embodiment may be implemented using existing technologies.

Claims

1. A boundary mode tapered concentrator based on a two-dimensional nodal line photonic crystal, characterized in that: The invention comprises a photonic crystal conical concentration region and a waveguide channel, wherein the photonic crystal conical concentration region and the waveguide channel are connected from left to right through photonic crystal structures I, II, III, IV and photonic crystal structure V to form a conical concentrator; the photonic crystal structure of the photonic crystal conical concentration region and the waveguide channel is composed of A1, A2, A3, A4, A5, B1, B2, B3, B4, B5 and O arranged in an overlapping manner; the photonic crystal is composed of a shell structure arranged in a hexagonal lattice, and the lattice constant a of the hexagonal lattice is 25 mm; The photonic crystal's unit cell o contains a shell structure, which is divided into three equal parts by digging out three rectangular areas. The width w of the rectangle is adjustable. The dielectric column in the shell structure is made of alumina dielectric material with a relative dielectric constant of 9.

5. The background material is air with a relative dielectric constant of 1. The inner radius of the dielectric column is R1 = 7.5mm, the outer radius is R2 = 10.5mm, and the height is d = 10mm. The various parameters of the photonic crystal can be freely adjusted according to the actual operating frequency of the concentrator. Move the dielectric column s at the bottom of the photonic crystal unit cell o to the right by distances of dc1=0.08a, dc2=0.1a, dc3=0.12a, dc4=0.14a, and dc5=0.16a, respectively. Based on the moved s and with the center of the unit cell as the origin, rotate it 120° counterclockwise and 120° clockwise to obtain photonic crystals a1, a2, a3, a4, and a5, respectively. Set the rightward movement of s as the positive direction. Move the dielectric column s at the bottom of the photonic crystal unit cell o to the left by distances of dc1 = 0.08a, dc2 = 0.1a, dc3 = 0.12a, dc4 = 0.14a, and dc5 = 0.16a, respectively. Based on the moved s, rotate the unit cell center 120° counterclockwise and 120° clockwise to obtain photonic crystals b1, b2, b3, b4, and b5, respectively. Set the leftward movement of s as the negative direction. The waveguide channel is formed by region V.

2. A boundary mode tapered concentrator based on a two-dimensional nodal line photonic crystal according to claim 1, characterized in that: The photonic crystal structure A1 is composed of photonic crystal primitive cells a1, wherein the x direction contains 8 primitive cells and the y direction contains 3 primitive cells; The photonic crystal structure A2 is composed of the photonic crystal a2, which contains 3 primitive cells in the x direction and 4 primitive cells in the y direction; The photonic crystal structure A3 is composed of a photonic crystal a3, which contains 4 primitive cells in the x direction and 5 primitive cells in the y direction; The photonic crystal structure A4 is composed of a photonic crystal a4, which contains 3 primitive cells in the x direction and 6 primitive cells in the y direction; The photonic crystal structure A5 is composed of the photonic crystal a5, which contains 9 primitive cells in the x direction and 7 primitive cells in the y direction; The photonic crystal structure B1 is composed of photonic crystal primitive cells b1, which contain 8 primitive cells in the x direction and 3 primitive cells in the y direction. The photonic crystal structure B2 is composed of the photonic crystal b2, which contains 3 primitive cells in the x direction and 4 primitive cells in the y direction; The photonic crystal structure B3 is composed of the photonic crystal b3, which contains 4 primitive cells in the x direction and 5 primitive cells in the y direction; The photonic crystal structure B4 is composed of the photonic crystal b4, which contains 3 primitive cells in the x direction and 6 primitive cells in the y direction; The photonic crystal structure B5 is composed of the photonic crystal b5, which contains 9 primitive cells in the x direction and 7 primitive cells in the y direction; The photonic crystal structures O1, O2, O3, O4, and O5 are composed of a photonic crystal unit cell o, which respectively contain 8, 3, 4, 3, and 9 unit cells in the x-direction; and 9, 7, 5, 3, and 1 unit cells in the y-direction.

3. A boundary mode tapered concentrator based on a two-dimensional nodal line photonic crystal according to claim 2, characterized in that: The concentrator is composed of five regions, and the upper, middle and lower parts of region I are arranged in the order of photonic crystal structures A1, O and B1; Region II of the concentrator is composed of photonic crystal structures A2, O and B2 arranged in sequence; region III of the concentrator is composed of photonic crystal structures A3, O and B3 arranged in sequence; region IV of the concentrator is composed of photonic crystal structures A4, O and B4 arranged in sequence; Region V of the concentrator is composed of photonic crystal structures A5, O and B5 arranged in sequence.

4. A boundary mode tapered concentrator based on a two-dimensional nodal line photonic crystal according to claim 3, characterized in that: The excitation source P1 and the output port P2 are respectively provided on both sides of the tapered concentrator; The excitation source P1 is located at the far left of the tapered concentrator; the output port P2 is located at the far right of the photonic crystal tapered concentrator.

5. A boundary mode tapered concentrator based on a two-dimensional nodal line photonic crystal according to claim 4, characterized in that: The concentrating area of ​​the boundary mode cone concentrator is composed of area I, area II, area III and area IV which are linked in sequence from left to right.

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