A topological optical communication device supporting one-dimensional topological boundary state optical waveguide and / or zero-dimensional topological corner state optical localization

Abstract

The present invention provides a topological optical communication device that supports one-dimensional topological boundary state optical waveguide and / or zero-dimensional topological angle state optical localization, which is composed of a first photonic crystal module PC1 and at least one of a second photonic crystal module PC2 and a third photonic crystal module PC3, wherein the first photonic crystal module PC1 and the second photonic crystal module PC2 and / or the third photonic crystal module PC3 have adjacent interfaces; the first photonic crystal module PC1, the second photonic crystal module PC2, and the third photonic crystal module PC3 are respectively composed of a first unit cell UC1 composed of a circular silicon dielectric column, a second unit cell UC2 composed of two semicircular silicon dielectric columns, and a third unit cell UC3 composed of four semicircular silicon dielectric columns arranged in a tetragonal lattice structure. The lattice constants of the first unit cell UC1, the second unit cell UC2, and the third unit cell UC3 are all a, and the dielectric column radius is all r. The topological optical communication device described in the present invention can support one-dimensional topological boundary state and zero-dimensional angle state.

Description

Technical Field

[0001] The invention belongs to the field of integrated optical communications and relates to a topological optical communication device that supports one-dimensional topological boundary state optical waveguide and / or zero-dimensional topological corner state optical localization. Background Art

[0002] In recent years, the superior localization and controllability of topological photonic crystals for optical signals have attracted extensive attention and further research. Under certain conditions, optical signals can be localized at the interface of two topological photonic crystals with different structures, thereby realizing robust transmission of the boundary states of optical signals. When two boundary states intersect at an intersection, the topological corner state that appears can localize the optical signal and complete the focusing and storage of the optical signal.

[0003] At present, the existing common topological photonic crystal structure consists of four small cylinders or cubes. Its structure manufacturing is relatively complex and requires high precision, which makes it difficult to manufacture. There are also preparation methods that use topological properties to achieve boundary states and corner states by drilling holes in materials, but this also causes serious waste of materials, high costs and is not conducive to environmental protection. Physical structures and preparation methods similar to the above are not conducive to integration. Summary of the invention

[0004] While the existing topological photonic crystal structure is difficult to prepare, not environmentally friendly, and not easy to integrate, this invention designs a topological optical communication device with a relatively simple structure, easy to prepare, and does not waste materials. The device is low in cost and easy to integrate, supports one-dimensional topological boundary state optical waveguides and / or zero-dimensional topological corner state optical localization, and can more conveniently meet the conditions and requirements of integrated optical communications.

[0005] The technical solution used in the present invention is:

[0006] A topological optical communication device supporting one-dimensional topological boundary state optical waveguide and / or zero-dimensional topological angle state optical localization, characterized in that it is composed of a first photonic crystal module PC1 and at least one of a second photonic crystal module PC2 and a third photonic crystal module PC3, and there is an adjacent interface between the first photonic crystal module PC1 and the second photonic crystal module PC2 and / or the third photonic crystal module PC3;

[0007] The first photonic crystal module PC1 is formed by arranging first unit cells UC1 according to a tetragonal lattice structure, and the first unit cell UC1 is formed by a circular silicon dielectric column with a cross-sectional radius of r in an air background;

[0008] The second photonic crystal module PC2 is formed by arranging the second unit cells UC2 in a tetragonal lattice structure, wherein the second unit cell UC2 is formed by two semicircular silicon dielectric columns with a cross-sectional radius of r in an air background, and the arc surfaces of the two semicircular silicon dielectric columns face the center of the second unit cell UC2;

[0009] The third photonic crystal module PC3 is formed by arranging the third unit cells UC3 in a tetragonal lattice structure, wherein the third unit cell UC3 is composed of four semicircular silicon dielectric columns with a cross-sectional radius of r in an air background, and the arc surfaces of the four semicircular silicon dielectric columns face the center of the third unit cell UC3;

[0010] The lattice constants of the first unit cell UC1, the second unit cell UC2, and the third unit cell UC3 are all a.

[0011] Furthermore, the cross-sectional radius r of the dielectric column of the first unit cell UC1 and the cross-sectional radius r of the semicircular silicon dielectric column of the second unit cell UC2 and the third unit cell UC3 are both 0.22a.

[0012] Furthermore, the lattice constant a=0.5 μm.

[0013] Furthermore, the first photonic crystal module PC1 and the second photonic crystal module PC2 have one interface, and a topological boundary state can be realized at the interface; the first photonic crystal module PC1 and the third photonic crystal module PC3 have one interface, and a topological boundary state can be realized at the interface.

[0014] Furthermore, there is a mutually perpendicular interface between the first photonic crystal module PC1 and the third photonic crystal module PC3, and zero-dimensional topological angular state light localization can be achieved at the intersection of the perpendicular interfaces.

[0015] Furthermore, the common photonic band gap of the first photonic crystal module PC1 and the second photonic crystal module PC2 is 161.9THz-236.4THz; the frequency range of the topological boundary state is 167.14THz-197.91THz; light with a frequency range of 167.14THz-197.91THz can be transmitted unidirectionally along the interface between the first photonic crystal module PC1 and the second photonic crystal module PC2; the common photonic band gap of the first photonic crystal module PC1 and the third photonic crystal module PC3 is 195THz-236.4THz; the frequency range of the topological boundary state is 195THz-204.3THz; light with a frequency range of 195THz-204.3THz can be transmitted along the interface between the first photonic crystal module PC1 and the third photonic crystal module PC3.

[0016] Furthermore, the third photonic crystal module PC3 is composed of 6×6 third unit cells, and the first photonic crystal module PC1 is composed of three rows of first unit cells UC1 outside the third photonic crystal module PC3; the first photonic crystal module PC1 and the third photonic crystal module PC3 have four interfaces that intersect with each other, and have four zero-dimensional topological angular state transmission channels.

[0017] Furthermore, the applicable frequency of the transmission channel of the four zero-dimensional topological corner states is 214 THz.

[0018] The topological optical communication device supporting one-dimensional topological boundary state optical waveguide and / or zero-dimensional topological corner state optical localization described in the present invention is composed of two photonic crystal structures with different topological properties. Circular dielectric column photonic crystals exhibit topologically mediocre properties and have topologically mediocre photonic band gaps; semicircular dielectric column photonic crystals exhibit topologically non-trivial properties, and their photonic band gaps have topologically non-trivial properties. There is a topological phase transition between the two photonic crystal structures. At the one-dimensional interface of two-dimensional circular dielectric column and semicircular dielectric column photonic crystals, light can be robustly transmitted within a certain frequency range and is robust to structural defects such as impurities and disorder; at the zero-dimensional intersection of two one-dimensional interfaces, light at several frequency points will be localized at the intersection and cannot propagate in the combined structure; it can support one-dimensional topological boundary state optical waveguide and zero-dimensional corner state optical localization.

[0019] The present invention designs a novel topological photonic crystal structure, a circular dielectric column and a semicircular dielectric column type photonic crystal in an air background, and the photonic crystal structure is relatively simple, with only a circular dielectric column or a semicircular dielectric column. And the combined structure of the circular dielectric column and the semicircular dielectric column type photonic crystal can simultaneously support one-dimensional topological boundary states and zero-dimensional angle states. It enables light to be robustly transmitted along the one-dimensional interface in the combined structure within a certain frequency; the light will be completely localized at the zero-dimensional intersection in the combined structure at a specific frequency, and has extremely strong light localization. The structural design is simple and easy to prepare, with a small volume, no waste in the preparation process, and has the advantages of low manufacturing cost, more environmental protection and conducive to integration. And it supports optical waveguides of one-dimensional topological boundary states and optical localization of zero-dimensional topological angle states; it has great application prospects in modern integrated optical communication devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 (a) is a schematic diagram of a 4×4 photonic crystal structure of a first photonic crystal module PC1 consisting of a silicon dielectric column with a circular cross section, where a is the lattice constant, r is the radius of the circular silicon dielectric column, ε r is the dielectric constant of the dielectric column, ε 0 is the dielectric constant of the air background;

[0021] (b) is a schematic diagram of a second photonic crystal module PC2 comprising two silicon dielectric pillars with semicircular cross sections arranged in a tetragonal lattice of 4×4;

[0022] (c) is the band diagram of a photonic crystal unit cell containing a single circular dielectric column, which has a mediocre band gap. The inset in the middle is a schematic diagram of the first Brillouin zone.

[0023] (d) is the band diagram of a photonic crystal unit cell containing two semicircular dielectric pillars, which has a topologically nontrivial band gap;

[0024] (e) is a structure of a third unit cell UC3 of a third photonic crystal module PC3 which is composed of four silicon dielectric pillars with semicircular cross sections;

[0025] (f) Electric field distribution along the X direction in the third unit cell UC3;

[0026] (g) Electric field distribution along the Y direction in the third unit cell UC3.

[0027] Figure 2 It is a schematic diagram of the combined structure of the first photonic crystal module PC1 and the second photonic crystal module PC2.

[0028] Figure 3 It is a schematic diagram of the supercell, dispersion curve and electric field distribution of the photonic crystal combination structure composed of the first photonic crystal module PC1 and the second photonic crystal module PC2. In the dispersion curve diagram, the band gap range is 160.1THz-239.38THz, and a curved curve in the band gap represents the boundary state, whose frequency range is 167.14THz-197.91THz, and the frequency corresponding to the electric field distribution is 193.92THz.

[0029] Figure 4 It is a combined structural diagram of the first photonic crystal module PC1 and the second photonic crystal module PC2 with impurities and disorder defects.

[0030] Figure 5 (a) is a schematic diagram of the transmission of an optical signal along a one-dimensional interface between the first photonic crystal module PC1 and the second photonic crystal module PC2;

[0031] (b) is a schematic diagram of the transmission of optical signals at the one-dimensional interface between PC1 with impurities and disorder defects and the second photonic crystal module PC2;

[0032] (c) is a schematic diagram of the transmission efficiency of the optical signal in the combination structure of the first photonic crystal module PC1 and the second photonic crystal module PC2 without defects;

[0033] (d) is a schematic diagram of the transmission efficiency of optical signals in the combination structure of the defective first photonic crystal module PC1 and the second photonic crystal module PC2.

[0034] Figure 6 (a) is a schematic diagram of the supercell of the combined structure of the first photonic crystal module PC1 and the third photonic crystal module PC3 and the electric field distribution at 195.99 THz;

[0035] (b) is the dispersion curve of the supercell structure composed of PC1 and the third photonic crystal module PC3. The curved curve in the middle represents the one-dimensional edge state. The dotted line appears between the edge state and the upper body state, representing the frequency of the zero-dimensional corner state.

[0036] Figure 7 The topological boundary state electric field distribution along the interface between the first photonic crystal module PC1 and the third photonic crystal module PC3 is shown, and the corresponding frequency is 197.2 THz.

[0037] Figure 8 (a) is a schematic diagram of the box-type combination structure composed of PC1 and PC3, where PC1 is arranged in three layers and PC3 is arranged in 6×6;

[0038] (b) is a schematic diagram of the eigenmode of the box structure composed of PC1 and PC3, where the four corner states are marked as C 1 ,C 2 ,C 3 ,C 4 .

[0039] Fig. 9 These are the two boundary state electric field distributions of the box-type combination structure of PC1 and PC3.

[0040] Fig.10 It is the electric field distribution diagram of the four corner states of the box-type combination structure of PC1 and PC3.

[0041] Fig.11 (a) is a schematic diagram of the box-type combination structure of PC1 and PC3 containing impurities and disorder defects;

[0042] (b) is the corner state electric field distribution diagram of the box-type combination structure of PC1 and PC3 in the presence of impurities and disorder defects at 213.27 THz, 214.1 THz, 214.1 THz, and 214.11 THz. DETAILED DESCRIPTION

[0043] In order to make the features, technical solutions and advantages of the present invention more clear, the present invention will be further described below in conjunction with specific embodiments and the accompanying drawings.

[0044] Figure 1 The present invention shows three crystal structures of topological optical communication devices that support one-dimensional topological boundary state optical waveguides and / or zero-dimensional topological corner state optical localization. Figure 1As shown in (a), the first photonic crystal module PC1 is composed of first unit cells UC1 arranged in a tetragonal lattice structure, wherein the first unit cell UC1 is composed of a circular silicon dielectric column with a cross-sectional radius of r in an air background. Figure 1 As shown in (b), the second unit cell UC2 is arranged in a tetragonal lattice structure. The second unit cell UC2 is composed of two semicircular silicon dielectric columns with a cross-sectional radius of r in the air background. The arc surfaces of the two semicircular silicon dielectric columns face the center of the second unit cell UC2. Figure 1 As shown in (e), the third photonic crystal module PC3 is composed of third unit cells UC3 arranged in a tetragonal lattice structure, and the third unit cell UC3 is composed of four semicircular silicon dielectric columns with a cross-sectional radius of r in an air background, and the arc surfaces of the four semicircular silicon dielectric columns face the center of the third unit cell UC3.

[0045] The first photonic crystal module PC1 is composed of a first unit cell UC1, which uses a silicon dielectric column with a circular cross section and has topologically mediocre properties, such as Figure 1 (c) shows the band diagram of a photonic crystal unit cell containing a single circular dielectric column, which has a mediocre band gap of 161.94THz-236.57THz. The inset in the middle is a schematic diagram of the first Brillouin zone, and the inset in the lower right corner shows the mirror-symmetric electric field distribution scanned in the X and Y directions respectively.

[0046] Photonic crystals containing semicircular silicon dielectric pillars have topologically nontrivial properties; e.g. Figure 1 As shown in (d), the band diagram of a photonic crystal unit cell containing two semicircular dielectric pillars has a topologically nontrivial band gap of 161.91 THz-236.50 THz. The inset in the lower right corner shows the electric field distribution diagram with mirror antisymmetry in the X direction and mirror symmetry in the Y direction, respectively.

[0047] like Figure 1 As shown in (e), the third unit cell UC3 contains four semicircular dielectric columns. Figure 1 (f) and (g) show that the electric field distribution has mirror antisymmetry along the X direction and the Y direction.

[0048] The dielectric columns of the first unit cell UC1, the second unit cell UC2, and the third unit cell UC3 are arranged in a tetragonal lattice structure and have the same lattice constant, which is a=0.5 μm, and the radius of the dielectric column is r=0.22a. There is a topological phase transition between the photonic crystals composed of circular dielectric columns and semicircular dielectric columns, and in the composite structure composed of the two photonic crystals, light can be robustly transmitted along the interface of the two photonic crystals.

[0049] The topological optical communication device supporting one-dimensional topological boundary state optical waveguide and / or zero-dimensional topological angle state optical localization described in the present invention is composed of a first photonic crystal module PC1 and at least one of a second photonic crystal module PC2 and a third photonic crystal module PC3, and there is an adjacent interface between the first photonic crystal module PC1 and the second photonic crystal module PC2 and / or the third photonic crystal module PC3.

[0050] Specifically, the electromagnetic wave studied in the present invention is the TM mode, the value of the lattice constant a is 0.5 μm, which represents the distance between the circular dielectric columns; the radius of the circular and semicircular silicon dielectric columns is r = 0.11 μm, that is, r = 0.22a, and the dielectric constant of the silicon material ε r =11.7, the dielectric constant of air background ε 0 = 1. The frequencies of topologically trivial and non-topologically trivial photonic band gaps are roughly the same: 161.9THz-236.5THz. In this frequency range, photons are localized, photon motion scattering is suppressed, and optical signals cannot propagate in the structure.

[0051] Example 1

[0052] Figure 2 The topological optical communication device with an interface constructed by the first photonic crystal module PC1 and the second photonic crystal module PC2 can realize the topological boundary state waveguide. In order to verify the one-dimensional boundary state between the first photonic crystal module PC1 composed of circular dielectric pillars and the second photonic crystal module PC2 composed of two semicircular dielectric pillars, Figure 2 The supercell structure of the first photonic crystal module PC1 and the second photonic crystal module PC2 shown in FIG. x Scan, solve the eigenvalue, calculate the frequency of the wave, and get Figure 3 As shown in the dispersion curve, there is a boundary state in the photonic band gap, and its frequency range is: 167.14THz-197.91THz. Therefore, only the optical signal within this frequency range can be transmitted along the interface between the first photonic crystal module PC1 and the second photonic crystal module PC2.

[0053] In order to verify the robustness of this transmission, a supercell structure with impurities and disorder defects is designed, which is constructed by the first photonic crystal module PC1 and the second photonic crystal module PC2. Figure 4 As shown, Figure 2 For comparison, the defect-free structure shown in Figure 5 The electric field distribution diagrams of the defect-free structure and the defective structure shown in (a) and (b), and Figure 5The comparison between the transmission efficiency of the defect-free structure and the defective structure shown in (c) and (d) shows that this boundary state transmission has strong robustness, and the transmission efficiency of both is maintained at around 95%.

[0054] Example 2

[0055] Constructing a crystal structure having an interface constructed by the first photonic crystal module PC1 and the third photonic crystal module PC3, Figure 6 (a) is a schematic diagram of the local structure of the crystal structure. At 195.99 THz, the electric field distribution in the crystal structure is as follows: Figure 6 (a) is shown on the right. In order to verify the one-dimensional boundary state between the first photonic crystal module PC1 composed of a circular dielectric column and the third photonic crystal module PC3 composed of four semicircular dielectric columns, Figure 6 The supercell structure shown in (a) scans the periodic wave vector k x , and its dispersion curve is as follows Figure 6 (b), the curved curve in the middle represents a one-dimensional edge state, that is, there is an edge state within the photonic band gap of 195THz-236.4THz, and the edge state frequency is 195THz-204.3THz. The dotted line appears between the edge state and the upper body state, representing the frequency of the zero-dimensional corner state. The approximate range of the corner state frequency can be determined by the frequencies of the body state and the edge state.

[0056] Figure 7 The boundary state waveguide electric field distribution diagram is shown, and it can be clearly seen that the energy is localized at the interface between the first photonic crystal module PC1 and the third photonic crystal module PC3.

[0057] Example 3

[0058] In order to verify that the intersection of the two different photonic crystal interfaces of the first photonic crystal module PC1 and the third photonic crystal module PC3 supports the zero-dimensional topological angle state of light localization, the following design is made: Figure 8 (a) is a box-type combination structure. The middle of the box-type structure is a 6×6 third photonic crystal module PC3 composed of a third unit cell containing four dielectric columns with semicircular cross-sections. The third photonic crystal module PC3 is surrounded by a first photonic crystal PC1 composed of three layers of dielectric columns with circular cross-sections. The radius of the dielectric columns in the first photonic crystal PC1 and the third photonic crystal module PC3 is r=0.11μm. The four vertically intersecting boundaries in the box-type combination structure provide four zero-dimensional intersections. The solution distribution obtained by performing energy band scanning on the box-type structure constructed by the first photonic crystal module PC1 and the third photonic crystal module PC3 is as follows: Figure 8 As shown in (b), there are four zero-dimensional topological corner states around 214 THz, which are marked as C 1 ,C 2,C 3 ,C 4 The frequencies corresponding to these four corner states are 214.11594THz, 214.116075THz, 214.116296THz, and 214.11932THz, respectively, which are distributed between the edge state and the bulk state in the photonic band gap.

[0059] Fig. 9 (a) and (b) are the boundary state distributions in the horizontal and vertical directions of the box-type combination structure composed of the first photonic crystal module PC1 and the third photonic crystal module PC3. It can be seen that in the box-type combination structure, the energy is still strictly localized at the interface of the photonic crystal modules with different topological characteristics.

[0060] Fig.10 The distribution of the four corner states of the box-type combination structure composed of the first photonic crystal module PC1 and the third photonic crystal module PC3 shows that the optical signal is confined to the four corners, which effectively realizes the strong localization of the optical signal.

[0061] In order to verify the robustness of zero-dimensional topological corner states, a box-shaped structure with disorder and impurity defects was constructed, such as Fig.11 (a) is shown. Obviously, although the corner state frequency has a slight shift, it still exists. The corner state electric field distribution at 213.27THz, 214.1THz, 214.1THz, and 214.11THz is shown in Fig.11 As shown in (b), it can be observed that the corner states are robust to defects in the structure.

[0062] The embodiments are preferred implementations of the present invention, but the present invention is not limited to the above-mentioned implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essential content of the present invention belong to the protection scope of the present invention.

Claims

1. A topological optical communication device supporting one-dimensional topological boundary state optical waveguide and / or zero-dimensional topological corner state optical localization, It is characterized in that It is composed of a first photonic crystal module PC1 and a third photonic crystal module PC3, wherein there is an adjacent interface between the first photonic crystal module PC1 and the third photonic crystal module PC3; The first photonic crystal module PC1 is formed by arranging first unit cells UC1 according to a tetragonal lattice structure, and the first unit cell UC1 is formed by a circular silicon dielectric column with a cross-sectional radius of r in an air background; The third photonic crystal module PC3 is formed by arranging the third unit cells UC3 in a tetragonal lattice structure, wherein the third unit cell UC3 is composed of four semicircular silicon dielectric columns with a cross-sectional radius of r in an air background, and the arc surfaces of the four semicircular silicon dielectric columns face the center of the third unit cell UC3; The lattice constants of the first unit cell UC1 and the third unit cell UC3 are both a; The first photonic crystal module PC1 and the third photonic crystal module PC3 have one interface, and a topological boundary state can be realized at the interface; Or there is a mutually perpendicular interface between the first photonic crystal module PC1 and the third photonic crystal module PC3, and zero-dimensional topological angular state light localization can be achieved at the intersection of the perpendicular interfaces; The common photonic band gap of the first photonic crystal module PC1 and the third photonic crystal module PC3 is 195THz-236.4THz; the frequency range of the topological boundary state is 195THz-204.3THz; and light with a frequency range of 195THz-204.3THz can be transmitted along the interface between the first photonic crystal module PC1 and the third photonic crystal module PC3.

2. The topological optical communication device according to claim 1, It is characterized in that The cross-sectional radius r of the dielectric column of the first unit cell UC1 and the cross-sectional radius r of the semicircular silicon dielectric column of the second unit cell UC2 and the third unit cell UC3 are both 0.22a.

3. The topological optical communication device according to claim 1, It is characterized in that The lattice constant a=0.5 μm.

4. The topological optical communication device according to claim 1, It is characterized in that The third photonic crystal module PC3 is composed of 6×6 third unit cells, and the first photonic crystal module PC1 is composed of three rows of first unit cells UC1 on the periphery of the third photonic crystal module PC3; the first photonic crystal module PC1 and the third photonic crystal module PC3 have four interfaces that intersect with each other and have four zero-dimensional topological angular state transmission channels.

5. The topological optical communication device according to claim 4, It is characterized in that The transmission channel of four zero-dimensional topological corner states is applicable to a frequency of 214THz.

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