CN114637074A - Optical device based on two-dimensional topological photonic crystal singular point and method thereof - Google Patents

Optical device based on two-dimensional topological photonic crystal singular point and method thereof Download PDF

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CN114637074A
CN114637074A CN202210247086.2A CN202210247086A CN114637074A CN 114637074 A CN114637074 A CN 114637074A CN 202210247086 A CN202210247086 A CN 202210247086A CN 114637074 A CN114637074 A CN 114637074A
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胡小永
龚旗煌
王晓晓
丁少奇
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    • G—PHYSICS
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    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
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Abstract

The invention discloses an optical device based on a two-dimensional topological photonic crystal singular point and a method thereof. The optical device comprises a traveling wave mode boundary state microcavity, a standing wave mode boundary state microcavity, an input/output boundary state waveguide, a connection boundary state waveguide and an input/output port; using two dimensions C6vDifferent modes of the boundary state waveguide and the boundary state microcavity of the symmetrical topological photonic crystal are coupled and adjusted to enable the whole optical device to be positioned at a singular point, so that the functions of an optical amplifier and an optical sensitive sensor are realized; all optical devices can be prepared by micro-nano processing, the modes of adjusting the reflectivity and the reflection phase are simple and easy to obtain, extra non-integratable structures and experimental devices are not needed, and the method has a huge application prospect in the field of on-chip integrated photonic devices; due to the protection of the topological photon energy band, the device has the function of resisting the influence of local structural defects and lattice disorder caused by micro-nano processing precision limitationAnd (4) robustness.

Description

Optical device based on two-dimensional topological photonic crystal singular point and method thereof
Technical Field
The invention relates to an optical device based on a two-dimensional topological photonic crystal singular point, and an implementation method and application thereof.
Background
A two-dimensional photonic crystal system is an important platform of micro-nano photonics, a photonic band gap is generated under the modulation effect of a periodic structure on incident electromagnetic waves, light with frequency in the photonic band gap cannot be transmitted, and the light is limited at the boundary or defect of the system, so that devices such as boundary state or defect state waveguides, micro-cavities and the like can be constructed. The manufacturing precision is limited in micro-nano processing, and defects and impurities in the device can cause light backscattering, so that the performance of the device is restricted; in addition, the photonic crystal line defect waveguide generates serious scattering under the condition of large-angle bending, and the application of the photonic crystal line defect waveguide in an optical information processing device is limited. The simultaneous degeneracy of the system's eigenvalues and eigenvectors at the EP (singular) point is generally applicable to high sensitivity sensing, generation of single mode low threshold lasers, on-chip opto-isolators, non-reciprocal mode converters, and construction of optical amplifiers. The structures such as the reflector and the Sagnac loop mirror are not beneficial to on-chip photonic integration due to the characteristics of large size and incompatibility, the mode of adjusting reflectivity and reflection phase is complex, the requirement on an experimental platform is high, and the operation and the realization are difficult. Whispering gallery microcavities are extremely sensitive to sidewall roughness, ambient environment, and preparation cleanliness, as foreign particles or rough sidewalls can cause mode changes, resulting in shifting, cleaving, and broadening. Therefore, the method for realizing the EP point by using the traditional echo wall microcavity, the waveguide and the reflecting device has the limitations that the complexity of adjusting the reflectivity and the reflecting phase is included, the system does not meet the requirements of an on-chip integrated photonic structure, the preparation accuracy is high, and the like.
The photonic crystal with the topological protection energy band in the inverted space is also called as a photonic topological insulator, the topological protection ensures that the topological boundary state waveguide and the microcavity have strong robustness, and the robustness of the topological boundary state waveguide can ensure strict one-way transmission even under the condition of large-angle bending and has the property of immunity to local defects and impurities; the robustness of the topological boundary state microcavity is realized in that the characteristic frequency of the microcavity cannot be disturbed as long as the area is unchanged even if the shape of the microcavity is different. In addition C6vThe symmetrical topological photonic crystal has the property of spin-orbit locking, the pseudo spin direction of the photon is locked with the transmission direction of light on the topological waveguide, namely, one pseudo spin direction corresponds to one lightThe two boundary states locked with the pseudo spin direction can be respectively transmitted to two opposite directions, and the two opposite directions respectively correspond to the pseudo spin direction of the photon to be upward and the pseudo spin direction to be downward; the topological boundary state microcavity has multiple characteristic frequencies which can be divided into a traveling wave mode and a standing wave mode, the phenomenon different from the coupling of the traditional microcavity and a waveguide can be generated after the topological boundary state microcavity is coupled with the topological boundary state waveguide, the pseudo spin of photons is not changed when the traveling wave mode is coupled, the photons are still transmitted along the locked track direction, the pseudo spin of the photons is reversed when the standing wave mode is coupled, so that the transmission direction along the track is changed, the phenomenon similar to reflection is realized, and the reflectivity and the reflection phase can be controlled by changing the coupling condition.
The protection of the topological photon energy band greatly improves the performance of the scheme of realizing the EP point by using the topological boundary state waveguide and the microcavity, meets the requirement of on-chip photon integration, is not influenced by local defects and lattice disorder of a sample structure, has higher tolerance on the defects caused by the limitation of micro-nano processing precision, and has important application prospect in the field of on-chip integrated photon chips.
The micro-nano optical waveguide and the reflector can enable the echo wall micro-cavity to work at an EP point, and have the functions of an optical amplifier and a sensitive sensor, however, the structure is very sensitive to the roughness of the side wall of the micro-cavity, and the mode of the micro-cavity is very easy to be influenced, so that the structure is limited by the precision of micro-nano processing, the structure of the reflector is not beneficial to on-chip photonic integration, and the reflectivity of the reflector is not adjustable. Although the Sagnac loop mirror can adjust parameters such as reflectivity and the like, the Sagnac loop mirror has high requirements on an experimental platform and also does not meet the requirements of an on-chip integrated photonic chip.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides an optical device based on a two-dimensional topological photonic crystal singular point, and an implementation method and application thereof.
One objective of the present invention is to provide an optical device based on two-dimensional topological photonic crystal singular points.
The traveling wave mode boundary state micro-cavity is internally provided with a hexagonal topological non-trivial lattice or a topological trivial lattice.
The traveling wave mode boundary state micro-cavity is internally provided with a hexagonal topological non-trivial lattice, and the optical device based on the two-dimensional topological photonic crystal singular point comprises: the device comprises a traveling wave mode boundary state microcavity, a standing wave mode boundary state microcavity, an input and output boundary state waveguide, a connection boundary state waveguide and an input and output port;
the traveling wave mode boundary state microcavity is provided with a hexagonal topological non-trivial lattice, the topological trivial lattice is spliced around the hexagonal topological non-trivial lattice, and a zero-dimensional traveling wave mode boundary state microcavity is formed at the interface of the hexagonal topological non-trivial lattice and the topological trivial lattice; the shape of the outer edge of the topological trivial lattice is a rectangle, and a pair of parallel sides of the rectangle is mutually parallel with a pair of parallel sides of the hexagon; the upper edge and the lower edge of the hexagonal topological non-trivial crystal lattice are respectively spaced from the upper edge and the lower edge of the rectangular topological trivial crystal lattice and have equal distances; the hexagonal topological trivial crystal lattice is arranged in the standing wave mode boundary state microcavity, the topological non-trivial crystal lattice is spliced around the hexagonal topological trivial crystal lattice, and a zero-dimensional standing wave mode boundary state microcavity is formed at the interface of the hexagonal topological trivial crystal lattice and the topological non-trivial crystal lattice; the shape of the outer edge of the topological non-trivial lattice is rectangular, and one pair of parallel sides of the rectangle and one pair of parallel sides of the hexagon are mutually parallel; the upper edge of the hexagonal topological trivial lattice is distant from the upper edge of the rectangular topological nontrivial lattice; the hexagonal topological nontrivial lattice in the traveling wave mode boundary state micro cavity is positioned on one side of the rectangular topological nontrivial lattice, and the hexagonal topological nontrivial lattice in the standing wave mode boundary state micro cavity is positioned on the other side of the rectangular topological nontrivial lattice, namely, a transverse distance is reserved between the hexagonal topological nontrivial lattice in the traveling wave mode boundary state micro cavity and the hexagonal topological nontrivial lattice in the standing wave mode boundary state micro cavity; the traveling wave mode boundary state microcavity is arranged above and the standing wave mode boundary state microcavity is arranged below, the lower edge of the rectangular topological trivial crystal lattice at the outer edge of the traveling wave mode boundary state microcavity is spliced with the upper edge of the rectangular topological nontrivial crystal lattice at the outer edge of the standing wave mode boundary state microcavity, and the rectangular topological trivial crystal lattice and the topological nontrivial crystal lattice interface form a one-dimensional connecting boundary state waveguide; the upper edge of the rectangular topological trivial lattice at the outer edge of the traveling wave mode boundary state microcavity is spliced with the rectangular topological nontrivial lattice, and a one-dimensional input and output boundary state waveguide is formed by an interface; the transmission directions of photons on the input and output boundary state waveguide and the connection boundary state waveguide are locked with the pseudo spin direction, namely the transmission directions of the photons with pseudo spins on the input and output boundary state waveguide and the connection boundary state waveguide are determined by the pseudo spin direction, and the pseudo spin direction changes the transmission direction; an input/output port is arranged at one end of the input/output boundary state waveguide, which is opposite to the hexagonal topological nontrivial lattice of the traveling wave mode boundary state microcavity; when inputting photons with pseudo-spin direction upward, the hexagonal topological nontrivial lattice in the traveling wave mode boundary state micro-cavity is positioned on the right side of the rectangular topological nontrivial lattice, the input/output port is positioned at the left end of the input/output boundary state waveguide, and the hexagonal topological nontrivial lattice in the standing wave mode boundary state micro-cavity is positioned on the left side of the rectangular topological nontrivial lattice; on the contrary, when inputting photons with pseudo-spin direction downward, the hexagonal topological non-trivial lattice in the traveling wave mode boundary state micro-cavity is positioned on the left side of the rectangular topological trivial lattice, the input and output ports are positioned on the right end of the input and output boundary state waveguide, and the hexagonal topological trivial lattice in the standing wave mode boundary state micro-cavity is positioned on the right side of the rectangular topological non-trivial lattice;
the side length of the hexagonal topological non-trivial lattice in the traveling wave mode boundary state microcavity is smaller than that of the hexagonal topological trivial lattice in the standing wave mode boundary state microcavity, so that one characteristic frequency of the traveling wave mode boundary state microcavity and one characteristic frequency of the standing wave mode boundary state microcavity are equal, namely the common characteristic frequency of the traveling wave mode boundary state microcavity and the standing wave mode boundary state microcavity, and under the common characteristic frequency, the traveling wave mode boundary state microcavity is located in a traveling wave mode, the traveling wave mode is two degenerate frequencies and simultaneously supports two pseudo-spinning photons transmitted in the clockwise direction and the anticlockwise direction; the standing wave mode boundary state microcavity is positioned in a standing wave mode, the standing wave mode is two splitting frequencies, and is caused by six 120-degree included angles of the hexagonal standing wave mode boundary state microcavity, energy flow is emitted outwards perpendicular to the standing wave mode boundary state microcavity, pseudo spin of photons is reversed, and the reflection function is realized;
light with common characteristic frequency and upward pseudo spin direction enters from an input/output port, is transmitted rightwards along an input/output boundary state waveguide, is coupled into a traveling wave mode boundary state microcavity and is transmitted anticlockwise along the traveling wave mode boundary state microcavity, is coupled to a connection boundary state waveguide through the traveling wave mode boundary state microcavity, is not changed in pseudo spin direction, is transmitted leftwards on the connection boundary state waveguide along a direction locked with the original pseudo spin direction, is coupled to a standing wave mode boundary state microcavity, and is inverted in pseudo spin direction through the standing wave mode boundary state microcavity, namely the pseudo spin direction is changed from upward to downward; light is coupled to the connection boundary state waveguide again, is transmitted rightwards along the connection boundary state waveguide in a reverse direction, realizes the function similar to reflection, is coupled to the traveling wave mode boundary state microcavity in the reverse direction and is transmitted clockwise along the traveling wave mode boundary state microcavity, is coupled to the input/output boundary state waveguide from the traveling wave mode boundary state microcavity and is transmitted leftwards in the reverse direction, and is finally output from the input/output port; similarly, light with a common characteristic frequency in a pseudo spin direction downward is incident from an input/output port, is transmitted leftward along the input/output boundary state waveguide, is coupled into the traveling wave mode boundary state microcavity and is transmitted clockwise along the traveling wave mode boundary state microcavity, is coupled to the connection boundary state waveguide through the traveling wave mode boundary state microcavity, is not changed in pseudo spin direction, is transmitted rightward on the connection boundary state waveguide along a direction locked with the original pseudo spin direction, is coupled to the standing wave mode boundary state microcavity, and is inverted in pseudo spin direction through the standing wave mode boundary state microcavity, namely the pseudo spin direction is changed from downward to upward; light is coupled to the connection boundary state waveguide again, is transmitted leftwards along the connection boundary state waveguide in a reverse direction, realizes the function similar to reflection, is coupled to the traveling wave mode boundary state microcavity in the reverse direction and is transmitted anticlockwise along the traveling wave mode boundary state microcavity, is coupled to the input/output boundary state waveguide from the traveling wave mode boundary state microcavity and is transmitted rightwards in the reverse direction, and is finally output from the input/output port; because the transmission in the traveling wave mode boundary state microcavity is also locked with the pseudo spin direction of photons, there is theoretically no coupling between clockwise transmission and counterclockwise transmission of the traveling wave mode boundary state microcavity, but because the coupling between clockwise transmission and counterclockwise transmission can occur due to the inevitable defects and the roughness of the side walls, the reflectivity and the reflection phase of the standing wave mode boundary state microcavity with the reflection function need to be adjusted, the reflectivity is adjusted by controlling the longitudinal distance between the standing wave mode boundary state microcavity and the connection boundary state waveguide, and the reflection phase is changed by the transverse distance between the standing wave mode boundary state microcavity and the traveling wave mode boundary state microcavity, so that the coupling between clockwise transmission and counterclockwise transmission is cancelled, the whole optical device is located at a singular point, and the effect of the optical amplifier is realized.
The traveling wave mode boundary state micro-cavity is internally provided with a hexagonal topological trivial lattice, and the optical device based on the two-dimensional topological photonic crystal singular point comprises: the device comprises a traveling wave mode boundary state microcavity, a standing wave mode boundary state microcavity, an input and output boundary state waveguide, a connection boundary state waveguide and an input and output port;
the traveling wave mode boundary state microcavity is provided with a hexagonal topological trivial lattice, the topological non-trivial lattice is spliced around the hexagonal topological trivial lattice, and a zero-dimensional traveling wave mode boundary state microcavity is formed at the interface of the hexagonal topological trivial lattice and the topological non-trivial lattice; the shape of the outer edge of the topological non-trivial lattice is rectangular, and one pair of parallel sides of the rectangle and one pair of parallel sides of the hexagon are mutually parallel; the upper edge and the lower edge of the hexagonal topological trivial crystal lattice are respectively distant from and equidistant to the upper edge and the lower edge of the rectangular topological nontrivial crystal lattice; the hexagonal topological non-trivial crystal lattice is arranged in the standing wave mode boundary state microcavity, the topological trivial crystal lattice is spliced around the hexagonal topological non-trivial crystal lattice, and a zero-dimensional standing wave mode boundary state microcavity is formed at the interface of the hexagonal topological non-trivial crystal lattice and the topological trivial crystal lattice; the shape of the outer edge of the topological trivial lattice is a rectangle, and a pair of parallel edges of the rectangle is mutually parallel to one pair of parallel edges of the hexagon; the upper edge of the hexagonal topological nontrivial lattice is spaced from the upper edge of the rectangular topological nontrivial lattice; the hexagonal topological trivial crystal lattice in the traveling wave mode boundary state micro-cavity is positioned on one side of the rectangular topological nontrivial crystal lattice, and the hexagonal topological nontrivial crystal lattice in the standing wave mode boundary state micro-cavity is positioned on the other side of the rectangular topological nontrivial crystal lattice, namely, a transverse distance is reserved between the hexagonal topological nontrivial crystal lattice in the traveling wave mode boundary state micro-cavity and the hexagonal topological nontrivial crystal lattice in the standing wave mode boundary state micro-cavity; the traveling wave mode boundary state microcavity is arranged above and the standing wave mode boundary state microcavity is arranged below, the lower edge of the rectangular topological non-trivial lattice at the outer edge of the traveling wave mode boundary state microcavity is spliced with the upper edge of the rectangular topological trivial lattice at the outer edge of the standing wave mode boundary state microcavity, and the rectangular topological non-trivial lattice and the topological trivial lattice interface form a one-dimensional connecting boundary state waveguide; the upper edge of the rectangular topological non-trivial crystal lattice at the outer edge of the traveling wave mode boundary state microcavity is spliced with the rectangular topological trivial crystal lattice, and a one-dimensional input and output boundary state waveguide is formed by an interface; the transmission directions of photons on the input and output boundary state waveguide and the connection boundary state waveguide are locked with the pseudo spin direction, namely the transmission directions of the photons with pseudo spins on the input and output boundary state waveguide and the connection boundary state waveguide are determined by the pseudo spin direction, and the pseudo spin direction changes the transmission direction; an input/output port is arranged at one end of the input/output boundary state waveguide, which is opposite to the hexagonal topological trivial lattice of the traveling wave mode boundary state microcavity; when photons with the pseudo-spin direction upward are input, the hexagonal topological trivial lattice in the traveling wave mode boundary state micro-cavity is positioned on the left side of the rectangular topological trivial lattice, the input and output ports are positioned at the right end of the input and output boundary state waveguide, and the hexagonal topological trivial lattice in the standing wave mode boundary state micro-cavity is positioned on the right side of the rectangular topological trivial lattice; on the contrary, when inputting photons with pseudo-spin direction downward, the hexagonal topological trivial lattice in the traveling wave mode boundary state micro-cavity is positioned on the right side of the rectangular topological trivial lattice, the input and output ports are positioned on the left end of the input and output boundary state waveguide, and the hexagonal topological trivial lattice in the standing wave mode boundary state micro-cavity is positioned on the left side of the rectangular topological trivial lattice;
the side length of the hexagonal topological trivial lattice in the traveling wave mode boundary state microcavity is smaller than that of the hexagonal topological non-trivial lattice in the standing wave mode boundary state microcavity, so that one characteristic frequency of the traveling wave mode boundary state microcavity and one characteristic frequency of the standing wave mode boundary state microcavity are equal, namely the common characteristic frequency of the traveling wave mode boundary state microcavity and the standing wave mode boundary state microcavity, and under the common characteristic frequency, the traveling wave mode boundary state microcavity is located in a traveling wave mode, the traveling wave mode is two degenerate frequencies and simultaneously supports two pseudo-spinning photons transmitted in the clockwise direction and the anticlockwise direction; the standing wave mode boundary state microcavity is positioned in a standing wave mode, the standing wave mode is two splitting frequencies, and is caused by six 120-degree included angles of the hexagonal standing wave mode boundary state microcavity, energy flow is emitted outwards perpendicular to the standing wave mode boundary state microcavity, pseudo spin of photons is reversed, and the reflection function is realized;
light with a common characteristic frequency in an upward pseudo-spin direction enters from an input/output port, is transmitted leftwards along an input/output boundary state waveguide, is coupled into a traveling wave mode boundary state microcavity and is transmitted clockwise along the traveling wave mode boundary state microcavity, is coupled to a connection boundary state waveguide through the traveling wave mode boundary state microcavity, is not changed in the pseudo-spin direction, is transmitted rightwards on the connection boundary state waveguide along a direction locked with the original pseudo-spin direction, is coupled to a standing wave mode boundary state microcavity, and is inverted in the pseudo-spin direction through the standing wave mode boundary state microcavity, namely the pseudo-spin direction is changed from downwards to upwards; light is coupled to the connection boundary state waveguide again, is transmitted leftwards along the connection boundary state waveguide in a reverse direction, realizes the function similar to reflection, is coupled to the traveling wave mode boundary state microcavity in the reverse direction and is transmitted anticlockwise along the traveling wave mode boundary state microcavity, is coupled to the input/output boundary state waveguide from the traveling wave mode boundary state microcavity and is transmitted rightwards in the reverse direction, and is finally output from the input/output port; similarly, light with a common characteristic frequency and a downward pseudo-spin direction enters from an input/output port, is transmitted rightwards along the input/output boundary state waveguide, is coupled into the traveling wave mode boundary state microcavity and is transmitted anticlockwise along the traveling wave mode boundary state microcavity, is coupled to the connection boundary state waveguide through the traveling wave mode boundary state microcavity, is not changed in pseudo-spin direction, is transmitted leftwards on the connection boundary state waveguide along a direction locked with the original pseudo-spin direction, is coupled to the standing wave mode boundary state microcavity, and is inverted in pseudo-spin direction through the standing wave mode boundary state microcavity, namely the pseudo-spin direction is changed from upwards to downwards; light is coupled to the connection boundary state waveguide again, is transmitted rightwards along the connection boundary state waveguide in a reverse direction, achieves a function similar to reflection, is coupled to the traveling wave mode boundary state microcavity in the reverse direction and is transmitted clockwise along the traveling wave mode boundary state microcavity, is coupled to the input and output boundary state waveguide from the traveling wave mode boundary state microcavity and is transmitted leftwards in the reverse direction, and is finally output from the input and output port; because the transmission in the traveling wave mode boundary state microcavity is also locked with the pseudo spin direction of photons, there is theoretically no coupling between clockwise transmission and counterclockwise transmission of the traveling wave mode boundary state microcavity, but because the coupling between clockwise transmission and counterclockwise transmission can occur due to the inevitable defects and the roughness of the side walls, the reflectivity and the reflection phase of the standing wave mode boundary state microcavity with the reflection function need to be adjusted, the reflectivity is adjusted by controlling the longitudinal distance between the standing wave mode boundary state microcavity and the connection boundary state waveguide, and the reflection phase is changed by the transverse distance between the standing wave mode boundary state microcavity and the traveling wave mode boundary state microcavity, so that the coupling between clockwise transmission and counterclockwise transmission is cancelled, the whole optical device is located at a singular point, and the effect of the optical amplifier is realized.
The topological trivial crystal lattice and the topological nontrivial crystal lattice are formed by punching holes on a background material, the topological trivial crystal lattice and the topological nontrivial crystal lattice respectively comprise a plurality of basic structure units which are closely arranged among crystal lattices, the outer edge of each basic structure unit is a regular hexagon, six orthotriangular air holes which are rotationally and symmetrically distributed are arranged in each basic structure unit, and the whole structure is provided with C6vSymmetry; in the topological trivial crystal lattice, the distance between the centers of six regular triangles and the center of a regular hexagon is less than 1/3 of the period of the two-dimensional topological photonic crystal, and the distance corresponds to a trivial topological state; in the topological nontrivial crystal lattice, the distance between the centers of six regular triangles and the center of a regular hexagon is greater than 1/3 of the period of the two-dimensional topological photonic crystal, and the six regular triangles correspond to nontrivial topological states; when the topological trivial crystal lattice and the topological non-trivial crystal lattice are spliced with each other, a boundary is formed at the spliced position, two topological boundary states with opposite slopes appear on a dispersion curve of the boundary in a forbidden band, and the two topological boundary states are respectivelyCorresponding to two different photon pseudo spin directions, namely pseudo spin direction up and pseudo spin direction down, and are localized near the boundary to transmit unidirectionally in opposite directions along the boundary.
The background material adopts silicon on insulator or silicon nitride; the equivalent two-dimensional refractive index of the silicon on insulator is 2.8, and the silicon on insulator is transparent in a 1550nm communication waveband; for an optical amplifier in a visible light waveband of 900nm, silicon nitride is used as a background material. The lateral distance between the topological nontrivial lattice of hexagons in the traveling wave mode boundary state microcavity and the topological nontrivial lattice of hexagons in the standing wave mode boundary state microcavity satisfies: 60-110 transverse periods, wherein the transverse period is the width of a hexagonal basic structural unit
Figure BDA0003545173790000061
R is the side length of the hexagonal basic structural unit.
The side length of the hexagonal topological non-trivial lattice in the traveling wave mode boundary state microcavity meets the following requirements: 5-7 Transverse Periods (TP); the side length of the hexagonal topological trivial lattice in the boundary state microcavity of the standing wave mode satisfies the following conditions: 13-16 transverse cycles; the longitudinal distance between the hexagonal topological trivial lattice in the standing wave mode boundary state microcavity and the waveguide connecting the boundary states satisfies the following conditions: 2-3 Longitudinal Periods (LP), wherein the longitudinal period is 3R/2 of the height of a row of hexagonal basic structural units, and R is the side length of the hexagonal basic structural units.
The longitudinal distance between the traveling wave mode boundary state microcavity and the connection boundary state waveguide is equal to the longitudinal distance between the traveling wave mode boundary state microcavity and the input/output boundary state waveguide, and the distance is 3-6 longitudinal periods.
The boundary state is bent and closed to form a topological microcavity, and the microcavity is robust in that the characteristic frequency of the microcavity is not influenced by the shape, namely the characteristic frequency and the mode of the microcavity are not changed as long as the area is unchanged regardless of the shape of the boundary. Boundary state microcavities have two types of characteristic frequencies: the device comprises a traveling wave mode and a standing wave mode, wherein the traveling wave mode is two degenerate frequencies and respectively corresponds to energy flow to rotate clockwise and anticlockwise along the microcavity, the standing wave mode is two splitting frequencies, the six 120-degree included angles of the hexagonal boundary state microcavity cause the energy flow to be emitted outwards perpendicular to the standing wave mode boundary state microcavity. Light with a specific pseudo spin direction is transmitted to the one-dimensional boundary state waveguide through the input waveguide corresponding to the photon pseudo spin direction; if the frequency of the light is not the same as any characteristic frequency of the boundary-state microcavity, the one-dimensional boundary-state waveguide and the zero-dimensional boundary-state microcavity are not coupled, and the light is output along the waveguide; if the frequency of the light is the same as one characteristic frequency of the boundary state microcavity, the one-dimensional boundary state waveguide is coupled with the zero-dimensional boundary state microcavity, when the characteristic frequency of the boundary state microcavity which is the same as the frequency of the light is the characteristic frequency of a traveling wave mode, traveling wave mode coupling occurs, the light with pseudo spin is coupled to the boundary state microcavity from the boundary state waveguide and then is coupled to the boundary state waveguide from the boundary state microcavity, the transmission direction is always locked with the pseudo spin and cannot be changed, and finally the light is output from the output waveguide along the direction which is the same as the transmission direction of the boundary state of the pseudo spin locking during incidence; when the characteristic frequency of the boundary state microcavity which is the same as the frequency of the light is the characteristic frequency of the standing wave mode, standing wave mode coupling occurs, when the light with certain pseudo spin is coupled to the boundary state microcavity from the boundary state waveguide, the pseudo spin is inverted, when the light is coupled to the boundary state waveguide from the boundary state microcavity, the transmission direction of the light on the boundary state locked with the pseudo spin is inverted, and finally the light is output from the output waveguide along the direction opposite to the transmission direction of the boundary state locked with the pseudo spin during incidence. Photon pseudo spin inversion caused by coupling between the standing wave modes of the boundary state waveguide and the boundary state microcavity resembles reflection and the reflectivity can be changed by the distance between the boundary state waveguide and the boundary state microcavity.
The invention also aims to provide a realization method of the optical device based on the two-dimensional topological photonic crystal singular point.
The invention discloses a method for realizing an optical device based on a two-dimensional topological photonic crystal singular point, wherein a topological nontrivial lattice which is hexagonal in a traveling wave mode boundary state micro cavity comprises the following steps:
1) preparing an optical device:
the traveling wave mode boundary state micro-cavity is internally provided with a hexagonal topological non-trivial lattice, and the periphery of the hexagonal topological non-trivial lattice is spliced with a topological trivial lattice of which the outer edge is rectangular; the hexagonal topological trivial crystal lattice is arranged in the boundary state microcavity of the standing wave mode, and the topological non-trivial crystal lattice with the rectangular outer edge is spliced around the hexagonal topological trivial crystal lattice; when inputting photons with pseudo-spin direction upward, the hexagonal topological nontrivial lattice in the traveling wave mode boundary state micro-cavity is positioned on the right side of the rectangular topological nontrivial lattice, the input/output port is positioned at the left end of the input/output boundary state waveguide, and the hexagonal topological nontrivial lattice in the standing wave mode boundary state micro-cavity is positioned on the left side of the rectangular topological nontrivial lattice; on the contrary, when inputting photons with pseudo-spin direction downward, the hexagonal topological non-trivial lattice in the traveling wave mode boundary state micro-cavity is positioned on the left side of the rectangular topological trivial lattice, the input and output ports are positioned on the right end of the input and output boundary state waveguide, and the hexagonal topological trivial lattice in the standing wave mode boundary state micro-cavity is positioned on the right side of the rectangular topological non-trivial lattice; the side length of the hexagonal topological non-trivial lattice in the traveling wave mode boundary state microcavity is smaller than that of the hexagonal topological trivial lattice in the standing wave mode boundary state microcavity, so that one characteristic frequency of the traveling wave mode boundary state microcavity and one characteristic frequency of the standing wave mode boundary state microcavity are equal, namely the common characteristic frequency of the traveling wave mode boundary state microcavity and the standing wave mode boundary state microcavity, and under the common characteristic frequency, the traveling wave mode boundary state microcavity is located in a traveling wave mode, the traveling wave mode is two degenerate frequencies and simultaneously supports two pseudo-spinning photons transmitted in the clockwise direction and the anticlockwise direction; the standing wave mode boundary state microcavity is positioned in a standing wave mode, the standing wave mode is two splitting frequencies, and is caused by six 120-degree included angles of the hexagonal standing wave mode boundary state microcavity, energy flow is emitted outwards perpendicular to the standing wave mode boundary state microcavity, pseudo spin of photons is reversed, and the reflection function is realized;
2) light with common characteristic frequency and upward pseudo spin direction enters from an input/output port, is transmitted rightwards along an input/output boundary state waveguide, is coupled into a traveling wave mode boundary state microcavity and is transmitted anticlockwise along the traveling wave mode boundary state microcavity, is coupled to a connection boundary state waveguide through the traveling wave mode boundary state microcavity, is not changed in pseudo spin direction, is transmitted leftwards on the connection boundary state waveguide along a direction locked with the original pseudo spin direction, is coupled to a standing wave mode boundary state microcavity, and is inverted in pseudo spin direction through the standing wave mode boundary state microcavity, namely the pseudo spin direction is changed from upward to downward; light is coupled to the connection boundary state waveguide again, is transmitted rightwards along the connection boundary state waveguide in a reverse direction, realizes the function similar to reflection, is coupled to the traveling wave mode boundary state microcavity in the reverse direction and is transmitted clockwise along the traveling wave mode boundary state microcavity, is coupled to the input/output boundary state waveguide from the traveling wave mode boundary state microcavity and is transmitted leftwards in the reverse direction, and is finally output from the input/output port;
3) similarly, light with a common characteristic frequency in a pseudo spin direction downward is incident from an input/output port, is transmitted leftward along the input/output boundary state waveguide, is coupled into the traveling wave mode boundary state microcavity and is transmitted clockwise along the traveling wave mode boundary state microcavity, is coupled to the connection boundary state waveguide through the traveling wave mode boundary state microcavity, is not changed in pseudo spin direction, is transmitted rightward on the connection boundary state waveguide along a direction locked with the original pseudo spin direction, is coupled to the standing wave mode boundary state microcavity, and is inverted in pseudo spin direction through the standing wave mode boundary state microcavity, namely the pseudo spin direction is changed from downward to upward; light is coupled to the connection boundary state waveguide again, is transmitted leftwards along the connection boundary state waveguide in a reverse direction, realizes the function similar to reflection, is coupled to the traveling wave mode boundary state microcavity in the reverse direction and is transmitted anticlockwise along the traveling wave mode boundary state microcavity, is coupled to the input/output boundary state waveguide from the traveling wave mode boundary state microcavity and is transmitted rightwards in the reverse direction, and is finally output from the input/output port;
4) since the transmission in the traveling wave mode boundary state microcavity is also locked to the pseudo spin direction of the photons, there is theoretically no coupling between the clockwise and counterclockwise transmission of the traveling-wave mode boundary-state microcavity, but the coupling between the clockwise transmission and the counter-clockwise transmission occurs due to the practically inevitable defects and the side wall roughness, it is therefore necessary to adjust the reflectivity and the reflection phase of the standing-wave mode boundary-state microcavity having a reflection function, the reflectivity is adjusted by controlling the longitudinal distance between the standing wave mode boundary state microcavity and the connecting boundary state waveguide, and changing the reflected phase by the lateral distance between the standing-wave mode boundary-state microcavity and the traveling-wave mode boundary-state microcavity, thereby canceling out the coupling between the clockwise transmission and the counterclockwise transmission, so that the whole optical device is positioned at a singular point, and the function of the optical amplifier is realized.
The invention discloses a method for realizing an optical device based on a two-dimensional topological photonic crystal singular point, wherein a hexagonal topological trivial lattice is arranged in a traveling wave mode boundary state micro cavity, and the method comprises the following steps:
1) preparing an optical device:
the traveling wave mode boundary state micro-cavity is internally provided with a hexagonal topological trivial lattice, and a topological non-trivial lattice with a rectangular outer edge is spliced around the hexagonal topological trivial lattice; the hexagonal topological non-trivial crystal lattice is arranged in the boundary state microcavity of the standing wave mode, and the topological trivial crystal lattice with the rectangular outer edge is spliced around the hexagonal topological non-trivial crystal lattice; when photons with the pseudo-spin direction upward are input, the hexagonal topological trivial lattice in the traveling wave mode boundary state micro-cavity is positioned on the left side of the rectangular topological trivial lattice, the input and output ports are positioned at the right end of the input and output boundary state waveguide, and the hexagonal topological trivial lattice in the standing wave mode boundary state micro-cavity is positioned on the right side of the rectangular topological trivial lattice; on the contrary, when inputting photons with pseudo-spin direction downward, the hexagonal topological trivial lattice in the traveling wave mode boundary state micro-cavity is positioned on the right side of the rectangular topological trivial lattice, the input and output ports are positioned on the left end of the input and output boundary state waveguide, and the hexagonal topological trivial lattice in the standing wave mode boundary state micro-cavity is positioned on the left side of the rectangular topological trivial lattice; the side length of the hexagonal topological trivial lattice in the traveling wave mode boundary state microcavity is smaller than that of the hexagonal topological non-trivial lattice in the standing wave mode boundary state microcavity, so that one characteristic frequency of the traveling wave mode boundary state microcavity and one characteristic frequency of the standing wave mode boundary state microcavity are equal, namely the common characteristic frequency of the traveling wave mode boundary state microcavity and the standing wave mode boundary state microcavity, and under the common characteristic frequency, the traveling wave mode boundary state microcavity is located in a traveling wave mode, the traveling wave mode is two degenerate frequencies and simultaneously supports two pseudo-spinning photons transmitted in the clockwise direction and the anticlockwise direction; the standing wave mode boundary state microcavity is positioned in a standing wave mode, the standing wave mode is two splitting frequencies, and is caused by six 120-degree included angles of the hexagonal standing wave mode boundary state microcavity, energy flow is emitted outwards perpendicular to the standing wave mode boundary state microcavity, pseudo spin of photons is reversed, and the reflection function is realized;
2) light with common characteristic frequency and upward pseudo-spin direction enters from an input/output port, is transmitted leftwards along an input/output boundary state waveguide, is coupled into a traveling wave mode boundary state microcavity and is transmitted clockwise along the traveling wave mode boundary state microcavity, is coupled to a connection boundary state waveguide through the traveling wave mode boundary state microcavity, is not changed in pseudo-spin direction, is transmitted rightwards on the connection boundary state waveguide along a direction locked with the original pseudo-spin direction, is coupled to a standing wave mode boundary state microcavity, and is inverted in pseudo-spin direction through the standing wave mode boundary state microcavity, namely the pseudo-spin direction is changed from upward to downward; light is coupled to the connection boundary state waveguide again, is transmitted leftwards along the reverse direction of the connection boundary state waveguide to realize the function similar to reflection, is coupled to the traveling wave mode boundary state microcavity and is transmitted anticlockwise along the traveling wave mode boundary state microcavity, is coupled from the traveling wave mode boundary state microcavity to the input/output boundary state waveguide to be transmitted rightwards in the reverse direction, and is finally output from the input/output port;
3) similarly, light with a common characteristic frequency in a pseudo spin direction downward is incident from an input/output port, is transmitted rightward along the input/output boundary state waveguide, is coupled into the traveling wave mode boundary state microcavity and is transmitted counterclockwise along the traveling wave mode boundary state microcavity, is coupled to the connection boundary state waveguide through the traveling wave mode boundary state microcavity, is not changed in pseudo spin direction, is transmitted leftward on the connection boundary state waveguide along a direction locked with the original pseudo spin direction, is coupled to the standing wave mode boundary state microcavity, and is inverted in pseudo spin direction through the standing wave mode boundary state microcavity, namely the pseudo spin direction is changed from downward to upward; light is coupled to the connection boundary state waveguide again, is transmitted rightwards along the connection boundary state waveguide in a reverse direction, realizes the function similar to reflection, is coupled to the traveling wave mode boundary state microcavity in the reverse direction and is transmitted clockwise along the traveling wave mode boundary state microcavity, is coupled to the input/output boundary state waveguide from the traveling wave mode boundary state microcavity and is transmitted leftwards in the reverse direction, and is finally output from the input/output port;
4) since the transmission in the traveling wave mode boundary state microcavity is also locked to the pseudo spin direction of the photons, there is theoretically no coupling between the clockwise and counterclockwise transmission of the traveling-wave mode boundary-state microcavity, but the coupling between the clockwise transmission and the counter-clockwise transmission occurs due to the practically inevitable defects and the side wall roughness, it is therefore necessary to adjust the reflectivity and the reflection phase of the standing-wave mode boundary-state microcavity having a reflection function, the reflectivity is adjusted by controlling the longitudinal distance between the standing wave mode boundary state microcavity and the connecting boundary state waveguide, and changing the reflected phase by the lateral distance between the standing-wave mode boundary-state microcavity and the traveling-wave mode boundary-state microcavity, thereby canceling out the coupling between the clockwise transmission and the counterclockwise transmission, so that the whole optical device is positioned at a singular point, and the function of the optical amplifier is realized.
The invention also aims to provide an application of the optical device based on the two-dimensional topological photonic crystal singular point as an optical amplifier and a high-sensitivity sensor.
The invention has the advantages that:
the invention proposes to use two-dimensional C6vDifferent modes of the boundary state waveguide and the boundary state microcavity of the symmetrical topological photonic crystal are coupled and adjusted to enable the whole optical device to be positioned at a singular point, so that the functions of an optical amplifier and an optical sensitive sensor are realized; all optical devices can be prepared by micro-nano processing, the modes of adjusting the reflectivity and the reflection phase are simple and easy to obtain, extra structures and experimental devices which cannot be integrated are not needed, and the method has a huge application prospect in the field of on-chip integrated photonic devices; due to the protectiveness of the topological photon energy band, the device has the robustness of resisting the influence of local structure defects and lattice disorder caused by the limitation of micro-nano processing precision.
Drawings
FIG. 1 is a schematic diagram of a first embodiment of a two-dimensional topological photonic crystal singular point-based optical device according to the present invention;
FIG. 2 is a schematic diagram of the splicing of a topological trivial lattice and a topological nontrivial lattice of an optical device based on a two-dimensional topological photonic crystal singular point according to the present invention
FIG. 3 is a diagram of a second embodiment of the two-dimensional topological photonic crystal singular point-based optical device according to the present invention;
fig. 4 is a schematic diagram of a three-dimensional topological photonic crystal singular point-based optical device according to a third embodiment of the present invention.
Detailed Description
The invention will be further elucidated by means of specific embodiments in the following with reference to the drawing.
Example one
As shown in fig. 1, the two-dimensional topological photonic crystal singular point-based optical device of the present embodiment of the present invention includes: the device comprises a traveling wave mode boundary state microcavity, a standing wave mode boundary state microcavity, an input/output boundary state waveguide, a connection boundary state waveguide and an input/output Port;
the traveling wave mode boundary state microcavity is provided with a hexagonal topological non-trivial lattice PhC2, the topological trivial lattice PhC1 is spliced around the hexagonal topological non-trivial lattice, and a zero-dimensional traveling wave mode boundary state microcavity is formed at the interface of the hexagonal topological non-trivial lattice and the topological trivial lattice; the shape of the outer edge of the topological trivial lattice is a rectangle, and a pair of parallel edges of the rectangle is mutually parallel to one pair of parallel edges of the hexagon; the upper edge and the lower edge of the hexagonal topological non-trivial crystal lattice are respectively spaced from the upper edge and the lower edge of the rectangular topological trivial crystal lattice and have equal distances; the hexagonal topological trivial crystal lattice PhC1 is arranged in the standing wave mode boundary state microcavity, the topological non-trivial crystal lattice PhC2 is spliced around the hexagonal topological trivial crystal lattice, and a zero-dimensional standing wave mode boundary state microcavity is formed at the interface of the hexagonal topological trivial crystal lattice and the topological non-trivial crystal lattice; the shape of the outer edge of the topological non-trivial lattice is a rectangle, and a pair of parallel sides of the rectangle and one pair of parallel sides of the hexagon are mutually parallel; the upper edge of the hexagonal topological trivial lattice is at a distance from the upper edge of the rectangular topological nontrivial lattice; the hexagonal topological nontrivial lattice in the traveling wave mode boundary state micro cavity is positioned on one side of the rectangular topological nontrivial lattice, and the hexagonal topological nontrivial lattice in the standing wave mode boundary state micro cavity is positioned on the other side of the rectangular topological nontrivial lattice, namely, a transverse distance is reserved between the hexagonal topological nontrivial lattice in the traveling wave mode boundary state micro cavity and the hexagonal topological nontrivial lattice in the standing wave mode boundary state micro cavity; the traveling wave mode boundary state microcavity is arranged above and the standing wave mode boundary state microcavity is arranged below, the lower edge of the rectangular topological trivial crystal lattice at the outer edge of the traveling wave mode boundary state microcavity is spliced with the upper edge of the rectangular topological nontrivial crystal lattice at the outer edge of the standing wave mode boundary state microcavity, and the rectangular topological trivial crystal lattice and the topological nontrivial crystal lattice interface form a one-dimensional connecting boundary state waveguide; the upper edge of the rectangular topological trivial crystal lattice at the outer edge of the traveling wave mode boundary state microcavity is spliced with the rectangular topological nontrivial crystal lattice PhC2, and the interface forms a one-dimensional input and output boundary state waveguide; the transmission directions of photons on the input and output boundary state waveguide and the connection boundary state waveguide are locked with the pseudo spin direction, namely the transmission directions of the photons with pseudo spins on the input and output boundary state waveguide and the connection boundary state waveguide are determined by the pseudo spin direction, and the pseudo spin direction changes the transmission direction; an input/output port is arranged at one end of the input/output boundary state waveguide, which is opposite to the hexagonal topological nontrivial lattice of the traveling wave mode boundary state microcavity; inputting photons with pseudo-upward spin directions, wherein the hexagonal topological non-trivial lattice in the traveling wave mode boundary state micro-cavity is positioned on the right side of the rectangular topological trivial lattice, the input/output Port is positioned at the left end of the input/output boundary state waveguide, and the hexagonal topological trivial lattice in the standing wave mode boundary state micro-cavity is positioned on the left side of the rectangular topological non-trivial lattice;
the side length of the hexagonal topological non-trivial lattice in the boundary state microcavity of the traveling wave mode is smaller than that of the hexagonal topological trivial lattice in the boundary state microcavity of the standing wave mode, so that one characteristic frequency of the boundary state microcavity of the traveling wave mode is equal to that of the boundary state microcavity of the standing wave mode, namely the characteristic frequency of the boundary state microcavity of the traveling wave mode is the common characteristic frequency of the boundary state microcavity of the standing wave mode and the boundary state microcavity of the traveling wave mode, and under the common characteristic frequency, the boundary state microcavity of the traveling wave mode is located in a traveling wave mode, the traveling wave mode is two degenerate frequencies and simultaneously supports two pseudo-spinning photons transmitted in the clockwise direction and the anticlockwise direction; the standing wave mode boundary state microcavity is positioned in a standing wave mode, the standing wave mode is two splitting frequencies, and is caused by six 120-degree included angles of the hexagonal standing wave mode boundary state microcavity, energy flow is emitted outwards perpendicular to the standing wave mode boundary state microcavity, pseudo spin of photons is reversed, and the reflection function is realized;
light with common characteristic frequency and upward pseudo spin direction enters from an input/output port, is transmitted rightwards along an input/output boundary state waveguide, is coupled into a traveling wave mode boundary state microcavity and is transmitted anticlockwise along the traveling wave mode boundary state microcavity, is coupled to a connection boundary state waveguide through the traveling wave mode boundary state microcavity, is not changed in pseudo spin direction, is transmitted leftwards on the connection boundary state waveguide along a direction locked with the original pseudo spin direction, is coupled to a standing wave mode boundary state microcavity, and is inverted in pseudo spin direction through the standing wave mode boundary state microcavity, namely the pseudo spin direction is changed from upward to downward; light is coupled to the connection boundary state waveguide again, is transmitted rightwards along the connection boundary state waveguide in a reverse direction, realizes the function similar to reflection, is coupled to the traveling wave mode boundary state microcavity in the reverse direction and is transmitted clockwise along the traveling wave mode boundary state microcavity, is coupled to the input/output boundary state waveguide from the traveling wave mode boundary state microcavity and is transmitted leftwards in the reverse direction, and is finally output from the input/output port; because the transmission in the traveling wave mode boundary state microcavity is also locked with the pseudo spin direction of photons, there is theoretically no coupling between clockwise transmission and counterclockwise transmission of the traveling wave mode boundary state microcavity, but because the coupling between clockwise transmission and counterclockwise transmission can occur due to the inevitable defects and the roughness of the side walls, the reflectivity and the reflection phase of the standing wave mode boundary state microcavity with the reflection function need to be adjusted, the reflectivity is adjusted by controlling the longitudinal distance between the standing wave mode boundary state microcavity and the connection boundary state waveguide, and the reflection phase is changed by the transverse distance between the standing wave mode boundary state microcavity and the traveling wave mode boundary state microcavity, so that the coupling between clockwise transmission and counterclockwise transmission is cancelled, the whole optical device is located at a singular point, and the effect of the optical amplifier is realized.
As shown in FIG. 2, the topological trivial crystal lattice PhC1 and the topological nontrivial crystal lattice PhC2 are formed by punching holes on a background material, the topological trivial crystal lattice and the topological nontrivial crystal lattice respectively comprise a plurality of basic structural units which are closely arranged among crystal lattices, the outer edge of each basic structural unit is a regular hexagon, six regular triangle air holes are symmetrically distributed in the basic structural units, and the overall structure is provided with C6vSymmetry; in the topological trivial crystal lattice, the distance between the centers of six regular triangles and the center of a regular hexagon is less than 1/3 of the period of the two-dimensional topological photonic crystal, and the six regular triangles correspond to trivial topological states; in the topological non-trivial crystal lattice, the distance between the centers of six regular triangles and the center of a regular hexagon is greater than 1/3 of the period of the two-dimensional topological photonic crystal, and the topological non-trivial topological state corresponds to; when the topological trivial crystal lattice and the topological non-trivial crystal lattice are spliced with each other, a boundary is formed at the spliced position, two topological boundary states with opposite slopes appear on a dispersion curve of the boundary in a forbidden band, the two topological boundary states respectively correspond to two different photon pseudo-spin directions, namely pseudo-spin direction upward and pseudo-spin direction downward, and are locally transmitted in a unidirectional mode near the boundary along the boundary in opposite directions.
In this example, the SOI is silicon on insulator, the thickness of silicon is 220nm, the silicon is a 2 μm thick silicon dioxide substrate, the two-dimensional equivalent refractive index near 1550nm is 2.8, as shown in FIG. 1, the basic structural units are regular hexagons, the side length R is 461nm, each basic structural unit has six rotationally symmetric regular triangle air holes inside, the side length is 276nm, and the depth is 220 nm. In the topologically trivial lattice PhC1 and the topologically nontrivial lattice PhC2, the centers of the regular triangles are 253nm (PhC1) and 277nm (PhC2), respectively, from the center of the regular hexagon. The topological trivial crystal lattice PhC1 and the topological nontrivial crystal lattice PhC2 are spliced to form a structure shown in a figure 2, the side length of a hexagonal topological nontrivial crystal lattice in a traveling wave mode boundary state microcavity is 6TP, the longitudinal distance between the traveling wave mode boundary state microcavity and an input/output boundary state waveguide is 4LP, and the longitudinal distance between the traveling wave mode boundary state microcavity and a connection boundary state waveguide is 4 LP; the side length of the hexagonal topological trivial lattice in the standing wave mode boundary state microcavity was 14TP, the longitudinal distance between the hexagonal topological trivial lattice in the standing wave mode boundary state microcavity and the connecting boundary state waveguide was 2LP, and the lateral distance between the hexagonal topological nontrivial lattice in the traveling wave mode boundary state microcavity and the center of the hexagonal topological trivial lattice in the standing wave mode boundary state microcavity was 75 TP. Ensures that a complete band gap exists near the central wavelength of 1550nm, and the band gap range is 1502 nm-1581 nm. The characteristic frequency of the traveling-wave mode boundary-state microcavity is 195.86THz, and the characteristic frequency of the standing-wave mode boundary-state microcavity is 195.87 THz.
Example two
In the embodiment, photons with pseudo-spin directions facing downwards are input, the hexagonal topological non-trivial lattice PhC2 in the boundary state microcavity of the traveling wave mode is positioned on the left side of the rectangular topological trivial lattice PhC1, the input/output Port is positioned at the right end of the input/output boundary state waveguide, and the hexagonal topological trivial lattice in the boundary state microcavity of the standing wave mode is positioned on the right side of the rectangular topological non-trivial lattice; light with a common characteristic frequency in a pseudo spin direction is incident from an input/output port, transmitted leftwards along an input/output boundary state waveguide, coupled into a traveling wave mode boundary state microcavity and transmitted clockwise along the traveling wave mode boundary state microcavity, coupled to a connection boundary state waveguide through the traveling wave mode boundary state microcavity, the pseudo spin direction is not changed, transmitted rightwards on the connection boundary state waveguide along a direction locked with the original pseudo spin direction, coupled to a standing wave mode boundary state microcavity, and the pseudo spin direction is reversed through the standing wave mode boundary state microcavity, namely the pseudo spin direction is changed from downward to upward; light is coupled to the connection boundary state waveguide again, is transmitted leftwards along the connection boundary state waveguide in a reverse direction, achieves a function similar to reflection, is coupled to the traveling wave mode boundary state microcavity in the reverse direction and is transmitted anticlockwise along the traveling wave mode boundary state microcavity, is coupled to the input/output boundary state waveguide from the traveling wave mode boundary state microcavity and is transmitted rightwards in the reverse direction, and is finally output from the input/output port. The other steps are the same as those of the first embodiment.
EXAMPLE III
In the embodiment, the traveling wave mode boundary state micro cavity is internally provided with a hexagonal topological trivial crystal lattice PhC1, and a topological nontrivial crystal lattice PhC2 is spliced around the hexagonal topological trivial crystal lattice; the hexagonal topological non-trivial crystal lattice is arranged in the boundary state microcavity of the standing wave mode, and the topological trivial crystal lattice is spliced around the hexagonal topological non-trivial crystal lattice; the hexagonal topological trivial lattice in the traveling wave mode boundary state microcavity is positioned on the right side of the rectangular topological trivial lattice, the input/output Port is positioned at the left end of the input/output boundary state waveguide, and the hexagonal topological trivial lattice in the standing wave mode boundary state microcavity is positioned on the left side of the rectangular topological trivial lattice. The other steps are the same as those of the first embodiment.
It is finally noted that the disclosed embodiments are intended to aid in the further understanding of the invention, but that those skilled in the art will appreciate that: various substitutions and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the invention should not be limited to the embodiments disclosed, but the scope of the invention is defined by the appended claims.

Claims (10)

1. An optical device based on two-dimensional topological photonic crystal singular points, the optical device comprising: the device comprises a traveling wave mode boundary state microcavity, a standing wave mode boundary state microcavity, an input and output boundary state waveguide, a connection boundary state waveguide and an input and output port;
the traveling wave mode boundary state micro-cavity is internally provided with a hexagonal topological non-trivial lattice, the topological trivial lattice is spliced around the hexagonal topological non-trivial lattice, and a zero-dimensional traveling wave mode boundary state micro-cavity is formed at the interface of the hexagonal topological non-trivial lattice and the topological trivial lattice; the shape of the outer edge of the topological trivial lattice is a rectangle, and a pair of parallel sides of the rectangle is mutually parallel with a pair of parallel sides of the hexagon; the upper edge and the lower edge of the hexagonal topological non-trivial crystal lattice are respectively spaced from the upper edge and the lower edge of the rectangular topological trivial crystal lattice and have equal distances; the hexagonal topological trivial crystal lattice is arranged in the standing wave mode boundary state microcavity, the topological nontrivial crystal lattice is spliced around the hexagonal topological trivial crystal lattice, and a zero-dimensional standing wave mode boundary state microcavity is formed at the interface of the hexagonal topological trivial crystal lattice and the topological nontrivial crystal lattice; the shape of the outer edge of the topological non-trivial lattice is a rectangle, and a pair of parallel sides of the rectangle and one pair of parallel sides of the hexagon are mutually parallel; the upper edge of the hexagonal topological trivial lattice is distant from the upper edge of the rectangular topological nontrivial lattice; the hexagonal topological non-trivial lattice in the traveling wave mode boundary state microcavity is positioned on one side of the rectangular topological trivial lattice, and the hexagonal topological trivial lattice in the standing wave mode boundary state microcavity is positioned on the other side of the rectangular topological non-trivial lattice, namely, a transverse distance is reserved between the hexagonal topological non-trivial lattice in the traveling wave mode boundary state microcavity and the hexagonal topological trivial lattice in the standing wave mode boundary state microcavity; the traveling wave mode boundary state microcavity is arranged above and the standing wave mode boundary state microcavity is arranged below, the lower edge of the rectangular topological trivial crystal lattice at the outer edge of the traveling wave mode boundary state microcavity is spliced with the upper edge of the rectangular topological nontrivial crystal lattice at the outer edge of the standing wave mode boundary state microcavity, and the rectangular topological trivial crystal lattice and the topological nontrivial crystal lattice interface form a one-dimensional connecting boundary state waveguide; the upper edge of the rectangular topological trivial lattice at the outer edge of the traveling wave mode boundary state microcavity is spliced with the rectangular topological nontrivial lattice, and a one-dimensional input and output boundary state waveguide is formed by an interface; the transmission directions of photons on the input and output boundary state waveguide and the connection boundary state waveguide are locked with the pseudo spin direction, namely the transmission directions of the photons with pseudo spins on the input and output boundary state waveguide and the connection boundary state waveguide are determined by the pseudo spin direction, and the pseudo spin direction changes the transmission direction; an input/output port is arranged at one end of the input/output boundary state waveguide, which is opposite to the hexagonal topological nontrivial lattice of the traveling wave mode boundary state microcavity; when inputting photons with pseudo-spin direction upward, the hexagonal topological nontrivial lattice in the traveling wave mode boundary state micro-cavity is positioned on the right side of the rectangular topological nontrivial lattice, the input/output port is positioned at the left end of the input/output boundary state waveguide, and the hexagonal topological nontrivial lattice in the standing wave mode boundary state micro-cavity is positioned on the left side of the rectangular topological nontrivial lattice; on the contrary, when inputting photons with pseudo-spin direction downward, the hexagonal topological non-trivial lattice in the traveling wave mode boundary state micro-cavity is positioned on the left side of the rectangular topological trivial lattice, the input and output ports are positioned on the right end of the input and output boundary state waveguide, and the hexagonal topological trivial lattice in the standing wave mode boundary state micro-cavity is positioned on the right side of the rectangular topological non-trivial lattice;
the side length of the hexagonal topological non-trivial lattice in the traveling wave mode boundary state microcavity is smaller than that of the hexagonal topological trivial lattice in the standing wave mode boundary state microcavity, so that one characteristic frequency of the traveling wave mode boundary state microcavity and one characteristic frequency of the standing wave mode boundary state microcavity are equal, namely the common characteristic frequency of the traveling wave mode boundary state microcavity and the standing wave mode boundary state microcavity, and under the common characteristic frequency, the traveling wave mode boundary state microcavity is located in a traveling wave mode, the traveling wave mode is two degenerate frequencies and simultaneously supports two pseudo-spinning photons transmitted in the clockwise direction and the anticlockwise direction; the standing wave mode boundary state microcavity is positioned in a standing wave mode, the standing wave mode is two splitting frequencies, and is caused by six 120-degree included angles of the hexagonal standing wave mode boundary state microcavity, energy flow is emitted outwards perpendicular to the standing wave mode boundary state microcavity, pseudo spin of photons is reversed, and the reflection function is realized;
light with a common characteristic frequency and an upward pseudospin direction enters from an input/output port, is transmitted rightwards along an input/output boundary state waveguide, is coupled into a traveling wave mode boundary state microcavity and is transmitted anticlockwise along the traveling wave mode boundary state microcavity, is coupled to a connection boundary state waveguide through the traveling wave mode boundary state microcavity, has no change in the pseudospin direction, is transmitted leftwards on the connection boundary state waveguide along a direction locked with the original pseudospin direction, is coupled to a standing wave mode boundary state microcavity, and enables the pseudospin direction to be reversed through the standing wave mode boundary state microcavity, namely the pseudospin direction is changed from upwards to downwards; light is coupled to the connection boundary state waveguide again, is transmitted rightwards along the connection boundary state waveguide in a reverse direction, realizes the function similar to reflection, is coupled to the traveling wave mode boundary state microcavity in the reverse direction and is transmitted clockwise along the traveling wave mode boundary state microcavity, is coupled to the input/output boundary state waveguide from the traveling wave mode boundary state microcavity and is transmitted leftwards in the reverse direction, and is finally output from the input/output port; similarly, light with a common characteristic frequency in a pseudo spin direction downward is incident from an input/output port, is transmitted leftward along the input/output boundary state waveguide, is coupled into the traveling wave mode boundary state microcavity and is transmitted clockwise along the traveling wave mode boundary state microcavity, is coupled to the connection boundary state waveguide through the traveling wave mode boundary state microcavity, is not changed in pseudo spin direction, is transmitted rightward on the connection boundary state waveguide along a direction locked with the original pseudo spin direction, is coupled to the standing wave mode boundary state microcavity, and is inverted in pseudo spin direction through the standing wave mode boundary state microcavity, namely the pseudo spin direction is changed from downward to upward; light is coupled to the connection boundary state waveguide again, is transmitted leftwards along the connection boundary state waveguide in a reverse direction, realizes the function similar to reflection, is coupled to the traveling wave mode boundary state microcavity in the reverse direction and is transmitted anticlockwise along the traveling wave mode boundary state microcavity, is coupled to the input/output boundary state waveguide from the traveling wave mode boundary state microcavity and is transmitted rightwards in the reverse direction, and is finally output from the input/output port; because the transmission in the traveling wave mode boundary state microcavity is also locked with the pseudo spin direction of photons, there is theoretically no coupling between clockwise transmission and counterclockwise transmission of the traveling wave mode boundary state microcavity, but because the coupling between clockwise transmission and counterclockwise transmission can occur due to the inevitable defects and the roughness of the side walls, the reflectivity and the reflection phase of the standing wave mode boundary state microcavity with the reflection function need to be adjusted, the reflectivity is adjusted by controlling the longitudinal distance between the standing wave mode boundary state microcavity and the connection boundary state waveguide, and the reflection phase is changed by the transverse distance between the standing wave mode boundary state microcavity and the traveling wave mode boundary state microcavity, so that the coupling between clockwise transmission and counterclockwise transmission is cancelled, the whole optical device is located at a singular point, and the effect of the optical amplifier is realized.
2. An optical device based on two-dimensional topological photonic crystal singular points, the optical device comprising: the device comprises a traveling wave mode boundary state microcavity, a standing wave mode boundary state microcavity, an input and output boundary state waveguide, a connection boundary state waveguide and an input and output port;
the traveling wave mode boundary state microcavity is provided with a hexagonal topological trivial lattice, the topological non-trivial lattice is spliced around the hexagonal topological trivial lattice, and a zero-dimensional traveling wave mode boundary state microcavity is formed at the interface of the hexagonal topological trivial lattice and the topological non-trivial lattice; the shape of the outer edge of the topological non-trivial lattice is rectangular, and one pair of parallel sides of the rectangle and one pair of parallel sides of the hexagon are mutually parallel; the upper edge and the lower edge of the hexagonal topological trivial crystal lattice are respectively spaced from the upper edge and the lower edge of the rectangular topological nontrivial crystal lattice by equal distances; the hexagonal topological nontrivial crystal lattice is arranged in the standing wave mode boundary state microcavity, the topological nontrivial crystal lattice is spliced around the hexagonal topological nontrivial crystal lattice, and a zero-dimensional standing wave mode boundary state microcavity is formed at the interface of the hexagonal topological nontrivial crystal lattice and the topological nontrivial crystal lattice; the shape of the outer edge of the topological trivial lattice is a rectangle, and a pair of parallel sides of the rectangle is mutually parallel with a pair of parallel sides of the hexagon; the upper edge of the hexagonal topological nontrivial lattice is spaced from the upper edge of the rectangular topological nontrivial lattice; the hexagonal topological trivial crystal lattice in the traveling wave mode boundary state micro-cavity is positioned on one side of the rectangular topological nontrivial crystal lattice, and the hexagonal topological nontrivial crystal lattice in the standing wave mode boundary state micro-cavity is positioned on the other side of the rectangular topological nontrivial crystal lattice, namely, a transverse distance is reserved between the hexagonal topological nontrivial crystal lattice in the traveling wave mode boundary state micro-cavity and the hexagonal topological nontrivial crystal lattice in the standing wave mode boundary state micro-cavity; the traveling wave mode boundary state microcavity is arranged above and the standing wave mode boundary state microcavity is arranged below, the lower edge of the rectangular topological non-trivial lattice at the outer edge of the traveling wave mode boundary state microcavity is spliced with the upper edge of the rectangular topological trivial lattice at the outer edge of the standing wave mode boundary state microcavity, and the rectangular topological non-trivial lattice and the topological trivial lattice interface form a one-dimensional connecting boundary state waveguide; the upper edge of the rectangular topological non-trivial crystal lattice at the outer edge of the traveling wave mode boundary state microcavity is spliced with the rectangular topological trivial crystal lattice, and a one-dimensional input and output boundary state waveguide is formed by an interface; the transmission directions of photons on the input and output boundary state waveguide and the connection boundary state waveguide are locked with the pseudo spin direction, namely the transmission directions of the photons with pseudo spins on the input and output boundary state waveguide and the connection boundary state waveguide are determined by the pseudo spin direction, and the pseudo spin direction changes the transmission direction; an input/output port is arranged at one end of the input/output boundary state waveguide, which is opposite to the hexagonal topological trivial lattice of the traveling wave mode boundary state microcavity; when photons with the pseudo-spin direction upward are input, the hexagonal topological trivial lattice in the boundary state microcavity of the traveling wave mode is positioned on the left side of the rectangular topological trivial lattice, the input and output ports are positioned at the right end of the input and output boundary state waveguide, and the hexagonal topological trivial lattice in the boundary state microcavity of the standing wave mode is positioned on the right side of the rectangular topological trivial lattice; on the contrary, when inputting photons with pseudo-spin direction downward, the hexagonal topological trivial lattice in the traveling wave mode boundary state micro-cavity is positioned on the right side of the rectangular topological trivial lattice, the input and output ports are positioned on the left end of the input and output boundary state waveguide, and the hexagonal topological trivial lattice in the standing wave mode boundary state micro-cavity is positioned on the left side of the rectangular topological trivial lattice;
the side length of the hexagonal topological trivial lattice in the traveling wave mode boundary state microcavity is smaller than that of the hexagonal topological nontrivial lattice in the standing wave mode boundary state microcavity, so that one characteristic frequency of the traveling wave mode boundary state microcavity and one characteristic frequency of the standing wave mode boundary state microcavity are equal, namely the common characteristic frequencies of the traveling wave mode boundary state microcavity and the standing wave mode boundary state microcavity are the common characteristic frequencies of the traveling wave mode boundary state microcavity and the standing wave mode boundary state microcavity; the standing wave mode boundary state microcavity is positioned in a standing wave mode, the standing wave mode is two splitting frequencies, and is caused by six 120-degree included angles of the hexagonal standing wave mode boundary state microcavity, energy flow is emitted outwards perpendicular to the standing wave mode boundary state microcavity, pseudo spin of photons is reversed, and the reflection function is realized;
light with a common characteristic frequency in an upward pseudo-spin direction enters from an input/output port, is transmitted leftwards along an input/output boundary state waveguide, is coupled into a traveling wave mode boundary state microcavity and is transmitted clockwise along the traveling wave mode boundary state microcavity, is coupled to a connection boundary state waveguide through the traveling wave mode boundary state microcavity, is not changed in the pseudo-spin direction, is transmitted rightwards on the connection boundary state waveguide along a direction locked with the original pseudo-spin direction, is coupled to a standing wave mode boundary state microcavity, and is inverted in the pseudo-spin direction through the standing wave mode boundary state microcavity, namely the pseudo-spin direction is changed from downwards to upwards; light is coupled to the connection boundary state waveguide again, is transmitted leftwards along the connection boundary state waveguide in a reverse direction, realizes the function similar to reflection, is coupled to the traveling wave mode boundary state microcavity in the reverse direction and is transmitted anticlockwise along the traveling wave mode boundary state microcavity, is coupled to the input/output boundary state waveguide from the traveling wave mode boundary state microcavity and is transmitted rightwards in the reverse direction, and is finally output from the input/output port; similarly, light with a common characteristic frequency in a downward pseudo spin direction enters from an input/output port, is transmitted rightwards along the input/output boundary state waveguide, is coupled into the traveling wave mode boundary state microcavity and is transmitted anticlockwise along the traveling wave mode boundary state microcavity, is coupled to the connection boundary state waveguide through the traveling wave mode boundary state microcavity, is not changed in the pseudo spin direction, is transmitted leftwards on the connection boundary state waveguide along a direction locked with the original pseudo spin direction, is coupled to the standing wave mode boundary state microcavity, and is inverted in the pseudo spin direction through the standing wave mode boundary state microcavity, namely the pseudo spin direction is changed from upwards to downwards; light is coupled to the connection boundary state waveguide again, is transmitted rightwards along the connection boundary state waveguide in a reverse direction, realizes the function similar to reflection, is coupled to the traveling wave mode boundary state microcavity in the reverse direction and is transmitted clockwise along the traveling wave mode boundary state microcavity, is coupled to the input/output boundary state waveguide from the traveling wave mode boundary state microcavity and is transmitted leftwards in the reverse direction, and is finally output from the input/output port; because the transmission in the traveling wave mode boundary state microcavity is also locked with the pseudo spin direction of photons, there is theoretically no coupling between clockwise transmission and counterclockwise transmission of the traveling wave mode boundary state microcavity, but because the coupling between clockwise transmission and counterclockwise transmission can occur due to the inevitable defects and the roughness of the side walls, the reflectivity and the reflection phase of the standing wave mode boundary state microcavity with the reflection function need to be adjusted, the reflectivity is adjusted by controlling the longitudinal distance between the standing wave mode boundary state microcavity and the connection boundary state waveguide, and the reflection phase is changed by the transverse distance between the standing wave mode boundary state microcavity and the traveling wave mode boundary state microcavity, so that the coupling between clockwise transmission and counterclockwise transmission is cancelled, the whole optical device is located at a singular point, and the effect of the optical amplifier is realized.
3. The optical device according to claim 1 or 2, wherein the topological trivial lattice and the topological non-trivial lattice are formed by punching holes on a background material, the topological trivial lattice and the topological non-trivial lattice respectively comprise a plurality of basic structural units which are closely arranged among the lattices, the outer edge of each basic structural unit is a regular hexagon, six air holes of a regular triangle are rotationally symmetrically distributed in the basic structural unit, and the overall structure has a C6vSymmetry; in the topological trivial crystal lattice, the distance between the centers of six regular triangles and the center of a regular hexagon is less than 1/3 of the period of the two-dimensional topological photonic crystal, and the distance corresponds to a trivial topological state; in the topological non-trivial crystal lattice, the distance between the centers of six regular triangles and the center of a regular hexagon is greater than 1/3 of the period of the two-dimensional topological photonic crystal, and the topological non-trivial crystal lattice corresponds to a non-trivial topological state; when the topological trivial crystal lattice and the topological non-trivial crystal lattice are spliced with each other, a boundary is formed at the spliced position, two topological boundary states with opposite slopes appear on a dispersion curve of the boundary in a forbidden band, the two topological boundary states respectively correspond to two different photon pseudo-spin directions, namely pseudo-spin direction upward and pseudo-spin direction downward, and are locally transmitted in a unidirectional mode near the boundary along the boundary in opposite directions.
4. An optical device as claimed in claim 3, characterized in that the background material is silicon-on-insulator or silicon nitride.
5. An optical device as claimed in claim 3, wherein the lateral distance between the topological nontrivial lattice of hexagons in the traveling-mode boundary-state microcavity and the topological nontrivial lattice of hexagons in the standing-wave-mode boundary-state microcavity is such that: 60-110 transverse periods, wherein the transverse period is the width of a hexagonal basic structural unit
Figure FDA0003545173780000052
R is the side length of the hexagonal basic structural unit.
6. An optical device as claimed in claim 3, wherein the side length of the topological nontrivial lattice of hexagons within the traveling wave mode boundary state microcavity satisfies: 5-7 transverse periods; the side length of the hexagonal topological trivial lattice in the boundary state microcavity of the standing wave mode satisfies the following conditions: 13-16 transverse periods, wherein the transverse period is the width of a hexagonal basic structural unit
Figure FDA0003545173780000051
R is the side length of the hexagonal basic structural unit.
7. An optical device according to claim 3, wherein the longitudinal distance between the topological trivial lattice of hexagons within the standing wave mode boundary state microcavity and the connecting boundary state waveguide satisfies: and 2-3 longitudinal periods, wherein the longitudinal period is 3R/2 of the height of the hexagonal basic structural unit, and R is the side length of the hexagonal basic structural unit.
8. A method for implementing a two-dimensional topological photonic crystal singular point based optical device according to claim 1, wherein said method comprises the steps of:
1) preparing an optical device:
the traveling wave mode boundary state micro-cavity is internally provided with a hexagonal topological non-trivial lattice, and the hexagonal topological non-trivial lattice is spliced with a topological trivial lattice with a rectangular outer edge around the hexagonal topological non-trivial lattice; the hexagonal topological trivial crystal lattice is arranged in the boundary state microcavity of the standing wave mode, and the topological non-trivial crystal lattice with the rectangular outer edge is spliced around the hexagonal topological trivial crystal lattice; when inputting photons with pseudo-spin direction upward, the hexagonal topological nontrivial lattice in the traveling wave mode boundary state micro-cavity is positioned on the right side of the rectangular topological nontrivial lattice, the input/output port is positioned at the left end of the input/output boundary state waveguide, and the hexagonal topological nontrivial lattice in the standing wave mode boundary state micro-cavity is positioned on the left side of the rectangular topological nontrivial lattice; on the contrary, when inputting photons with pseudo-spin direction downward, the hexagonal topological non-trivial lattice in the traveling wave mode boundary state micro-cavity is positioned on the left side of the rectangular topological trivial lattice, the input and output ports are positioned on the right end of the input and output boundary state waveguide, and the hexagonal topological trivial lattice in the standing wave mode boundary state micro-cavity is positioned on the right side of the rectangular topological non-trivial lattice;
the side length of the hexagonal topological non-trivial lattice in the traveling wave mode boundary state microcavity is smaller than that of the hexagonal topological trivial lattice in the standing wave mode boundary state microcavity, so that one characteristic frequency of the traveling wave mode boundary state microcavity and one characteristic frequency of the standing wave mode boundary state microcavity are equal, namely the common characteristic frequency of the traveling wave mode boundary state microcavity and the standing wave mode boundary state microcavity, and under the common characteristic frequency, the traveling wave mode boundary state microcavity is located in a traveling wave mode, the traveling wave mode is two degenerate frequencies and simultaneously supports two pseudo-spinning photons transmitted in the clockwise direction and the anticlockwise direction; the standing wave mode boundary state microcavity is positioned in a standing wave mode, the standing wave mode is two splitting frequencies, and is caused by six 120-degree included angles of the hexagonal standing wave mode boundary state microcavity, energy flow is emitted outwards perpendicular to the standing wave mode boundary state microcavity, pseudo spin of photons is reversed, and the reflection function is realized;
2) light with common characteristic frequency and upward pseudo spin direction enters from an input/output port, is transmitted rightwards along an input/output boundary state waveguide, is coupled into a traveling wave mode boundary state microcavity and is transmitted anticlockwise along the traveling wave mode boundary state microcavity, is coupled to a connection boundary state waveguide through the traveling wave mode boundary state microcavity, is not changed in pseudo spin direction, is transmitted leftwards on the connection boundary state waveguide along a direction locked with the original pseudo spin direction, is coupled to a standing wave mode boundary state microcavity, and is inverted in pseudo spin direction through the standing wave mode boundary state microcavity, namely the pseudo spin direction is changed from upward to downward; light is coupled to the connection boundary state waveguide again, is transmitted rightwards along the connection boundary state waveguide in a reverse direction, realizes the function similar to reflection, is coupled to the traveling wave mode boundary state microcavity in the reverse direction and is transmitted clockwise along the traveling wave mode boundary state microcavity, is coupled to the input/output boundary state waveguide from the traveling wave mode boundary state microcavity and is transmitted leftwards in the reverse direction, and is finally output from the input/output port;
3) similarly, light with a common characteristic frequency in a pseudo spin direction downward is incident from an input/output port, is transmitted leftward along the input/output boundary state waveguide, is coupled into the traveling wave mode boundary state microcavity and is transmitted clockwise along the traveling wave mode boundary state microcavity, is coupled to the connection boundary state waveguide through the traveling wave mode boundary state microcavity, is not changed in pseudo spin direction, is transmitted rightward on the connection boundary state waveguide along a direction locked with the original pseudo spin direction, is coupled to the standing wave mode boundary state microcavity, and is inverted in pseudo spin direction through the standing wave mode boundary state microcavity, namely the pseudo spin direction is changed from downward to upward; light is coupled to the connection boundary state waveguide again, is transmitted leftwards along the connection boundary state waveguide in a reverse direction, realizes the function similar to reflection, is coupled to the traveling wave mode boundary state microcavity in the reverse direction and is transmitted anticlockwise along the traveling wave mode boundary state microcavity, is coupled to the input/output boundary state waveguide from the traveling wave mode boundary state microcavity and is transmitted rightwards in the reverse direction, and is finally output from the input/output port;
4) since the transmission in the traveling wave mode boundary state microcavity is also locked to the pseudo spin direction of the photons, there is theoretically no coupling between the clockwise and counterclockwise transmission of the traveling-wave mode boundary-state microcavity, but the coupling between the clockwise transmission and the counter-clockwise transmission occurs due to the practically inevitable defects and the side wall roughness, it is therefore necessary to adjust the reflectivity and reflection phase of the standing-wave mode boundary-state microcavity having a reflection function, the reflectivity is adjusted by controlling the longitudinal distance between the standing wave mode boundary state microcavity and the connecting boundary state waveguide, and changing the reflected phase by the lateral distance between the standing-wave mode boundary-state microcavity and the traveling-wave mode boundary-state microcavity, thereby canceling out the coupling between the clockwise transmission and the counterclockwise transmission, so that the whole optical device is positioned at a singular point, and the function of the optical amplifier is realized.
9. A method for implementing a two-dimensional topological photonic crystal singular point based optical device according to claim 2, wherein said method comprises the steps of:
1) preparing an optical device:
the traveling wave mode boundary state micro-cavity is internally provided with a hexagonal topological trivial lattice, and a topological non-trivial lattice with a rectangular outer edge is spliced around the hexagonal topological trivial lattice; the hexagonal topological nontrivial crystal lattice is arranged in the standing wave mode boundary state microcavity, and the topological nontrivial crystal lattice with the rectangular outer edge is spliced around the hexagonal topological nontrivial crystal lattice; when photons with the pseudo-spin direction upward are input, the hexagonal topological trivial lattice in the traveling wave mode boundary state micro-cavity is positioned on the left side of the rectangular topological trivial lattice, the input and output ports are positioned at the right end of the input and output boundary state waveguide, and the hexagonal topological trivial lattice in the standing wave mode boundary state micro-cavity is positioned on the right side of the rectangular topological trivial lattice; on the contrary, when inputting photons with pseudo-spin direction downward, the hexagonal topological trivial lattice in the traveling wave mode boundary state micro-cavity is positioned on the right side of the rectangular topological trivial lattice, the input and output ports are positioned on the left end of the input and output boundary state waveguide, and the hexagonal topological trivial lattice in the standing wave mode boundary state micro-cavity is positioned on the left side of the rectangular topological trivial lattice;
the side length of the hexagonal topological trivial lattice in the traveling wave mode boundary state microcavity is smaller than that of the hexagonal topological non-trivial lattice in the standing wave mode boundary state microcavity, so that one characteristic frequency of the traveling wave mode boundary state microcavity and one characteristic frequency of the standing wave mode boundary state microcavity are equal, namely the common characteristic frequency of the traveling wave mode boundary state microcavity and the standing wave mode boundary state microcavity, and under the common characteristic frequency, the traveling wave mode boundary state microcavity is located in a traveling wave mode, the traveling wave mode is two degenerate frequencies and simultaneously supports two pseudo-spinning photons transmitted in the clockwise direction and the anticlockwise direction; the standing wave mode boundary state microcavity is positioned in a standing wave mode, the standing wave mode is two splitting frequencies, and is caused by six 120-degree included angles of the hexagonal standing wave mode boundary state microcavity, energy flow is emitted outwards perpendicular to the standing wave mode boundary state microcavity, pseudo spin of photons is reversed, and the reflection function is realized;
2) light with common characteristic frequency and upward pseudo-spin direction enters from an input/output port, is transmitted leftwards along an input/output boundary state waveguide, is coupled into a traveling wave mode boundary state microcavity and is transmitted clockwise along the traveling wave mode boundary state microcavity, is coupled to a connection boundary state waveguide through the traveling wave mode boundary state microcavity, is not changed in pseudo-spin direction, is transmitted rightwards on the connection boundary state waveguide along a direction locked with the original pseudo-spin direction, is coupled to a standing wave mode boundary state microcavity, and is inverted in pseudo-spin direction through the standing wave mode boundary state microcavity, namely the pseudo-spin direction is changed from upward to downward; light is coupled to the connection boundary state waveguide again, is transmitted leftwards along the connection boundary state waveguide in a reverse direction, realizes the function similar to reflection, is coupled to the traveling wave mode boundary state microcavity in the reverse direction and is transmitted anticlockwise along the traveling wave mode boundary state microcavity, is coupled to the input/output boundary state waveguide from the traveling wave mode boundary state microcavity and is transmitted rightwards in the reverse direction, and is finally output from the input/output port;
3) similarly, light with a common characteristic frequency in a downward pseudo spin direction enters from an input/output port, is transmitted rightward along the input/output boundary state waveguide, is coupled into the traveling wave mode boundary state microcavity and is transmitted counterclockwise along the traveling wave mode boundary state microcavity, is coupled to the connection boundary state waveguide through the traveling wave mode boundary state microcavity, is not changed in the pseudo spin direction, is transmitted leftward on the connection boundary state waveguide along a direction locked with the original pseudo spin direction, is coupled to the standing wave mode boundary state microcavity, and is inverted in the pseudo spin direction through the standing wave mode boundary state microcavity, namely the pseudo spin direction is changed from downward to upward; light is coupled to the connection boundary state waveguide again, is transmitted rightwards along the connection boundary state waveguide in a reverse direction, achieves a function similar to reflection, is coupled to the traveling wave mode boundary state microcavity in the reverse direction and is transmitted clockwise along the traveling wave mode boundary state microcavity, is coupled to the input and output boundary state waveguide from the traveling wave mode boundary state microcavity and is transmitted leftwards in the reverse direction, and is finally output from the input and output port;
4) since the transmission in the traveling wave mode boundary state microcavity is also locked to the pseudo spin direction of the photons, there is theoretically no coupling between the clockwise and counterclockwise transmission of the traveling-wave mode boundary-state microcavity, but the coupling between the clockwise transmission and the counter-clockwise transmission occurs due to the practically inevitable defects and the side wall roughness, it is therefore necessary to adjust the reflectivity and the reflection phase of the standing-wave mode boundary-state microcavity having a reflection function, the reflectivity is adjusted by controlling the longitudinal distance between the standing wave mode boundary state microcavity and the connecting boundary state waveguide, and the reflection phase is changed by the lateral distance between the standing wave mode boundary state microcavity and the traveling wave mode boundary state microcavity, thereby canceling out the coupling between the clockwise transmission and the counterclockwise transmission, so that the whole optical device is positioned at a singular point, and the function of the optical amplifier is realized.
10. Use of the two-dimensional topological photonic crystal singular point based optical device according to claim 1 or 2 as an optical amplifier and a high sensitivity sensor.
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