A non-periodic photonic multilayer structure for phase modulation coding

Abstract

The present invention provides a non-periodic photon multilayer structure that can be used for phase modulation encoding, belonging to the technical field of phase modulation encoders. The non-periodic photon multilayer structure includes two Thue-Morse sequences with parity-time symmetric distribution, Thue-Morse sequence S N The iteration rule is: when N = 1, S2 = A, when N ≥ 2, S N =S N‑1 (S N‑1 The A in is replaced by AB, S N‑1 B in the sequence is replaced by BA), A is the first dielectric layer; B is the second dielectric layer; wherein the subscript N is the ordinal number of the sequence, the first dielectric layer and the second dielectric layer are two uniform dielectric sheets with different refractive indices, and there are also two layers of graphene sheets in the Thue-Morse sequence, and the graphene sheets are respectively embedded between two adjacent second dielectric layers. The present invention can form a phase jump to be applied to numerical coding.

Description

Technical Field

[0001] The invention belongs to the technical field of phase modulation encoders and relates to a non-periodic photon multilayer structure that can be used for phase modulation encoding. Background Art

[0002] An encoder is a device that compiles and converts signals (such as bit streams) or data into a signal form that can be used for communication, transmission and storage. In optical fiber sensors, phase modulation technology can be used to periodically and quickly encode the phases of pump light and probe light. The faster the phase modulation speed, the higher the spatial resolution of the phase modulation technology. At the same time, by changing the width of the phase encoding, the position of the correlation peaks other than the zero-order correlation peak can be moved in the optical fiber, thereby achieving distributed measurement. Compared with amplitude modulation and frequency modulation encoding technology, phase modulation encoding does not have the problem of mutual restriction between spatial resolution and measurement range, and by changing the width of the phase encoding, the correlation peak can be scanned in the optical fiber to be measured for distributed measurement.

[0003] In the process of phase modulation encoding, the phase change of light waves is closely related to the optical system structure of the material. Parity-time (PT) symmetric structure can achieve regular phase changes. PT symmetric optical system is a special non-Hermitian structure that can enhance resonance. Studies have shown that the maximum transmittance points and minimum reflectance points of light waves incident on the PT symmetric structure from different directions do not coincide; the light waves incident on the PT structure in the forward and reverse directions have the same transmission characteristics, but their reflection characteristics are different. There is a phase mutation in the reflection coefficient phase at the zero reflection point, and the non-reciprocity of reflection makes the positions of the left and right reverse coefficient phase mutations not coincide. This effect can be applied to phase modulation encoding. Non-photonic crystals have more defect cavities and transmission films than periodic and quasi-periodic photonic crystals. Therefore, PT symmetry and non-periodic photonic crystals can be combined to achieve multi-value phase encoding.

[0004] Graphene is an ultra-thin two-dimensional material with excellent electrical conductivity, and its surface conductivity can be flexibly adjusted by chemical potential. When graphene is embedded in a photonic crystal, the zero point of the reflectivity will be affected by graphene, so the phase jump position of the reflectivity can be regulated by the chemical potential of graphene, thereby controlling the phase modulation coding. Summary of the invention

[0005] The purpose of the present invention is to provide a non-periodic photonic multilayer structure that can be used for phase modulation coding in order to address the above-mentioned problems existing in the prior art. The technical problem to be solved by the present invention is how to make the multilayer structure form a phase jump of the reflection coefficient for application in numerical coding.

[0006] The object of the present invention can be achieved by the following technical solutions: A non-periodic photon multilayer structure that can be used for phase modulation coding, characterized in that the non-periodic photon multilayer structure comprises two symmetrically distributed Thue-Morse sequences, the Thue-Morse sequence S N The iteration rule is: S 1 =A,N=1;S 2 =AB, N=2; S N =S N-1 (A→AB, B→BA), N≥3, where S N-1 A→AB means A is replaced by AB, B→BA means B is replaced by BA, N is the sequence number, S N represents the Nth item of the sequence; A is the first dielectric layer; B is the second dielectric layer; the first dielectric layer and the second dielectric layer are two uniform dielectric sheets with different refractive indices, and there is also a graphene sheet layer in the Thue-Morse sequence, and the graphene sheet layer is embedded between two adjacent second dielectric layers;

[0007] The first dielectric layer located on one side of the symmetry center of the non-periodic photonic multilayer structure is called the first lossy dielectric layer, and its refractive index in the light-transmitting state is expressed as n a The first dielectric layer located on the other side of the symmetry center of the non-periodic photon multilayer structure is called the first gain dielectric layer, and its refractive index in the light-transmitting state is expressed as n a' The second dielectric layer on the same side as the first gain dielectric layer is called the second gain dielectric layer, and its refractive index in the light-transmitting state is expressed as n b The second dielectric layer on the same side as the first lossy dielectric layer is called the second lossy dielectric layer, and its refractive index in the light-transmitting state is represented by n b' ;

[0008] n a =n A +0.01qi,n a' =n A –0.01qi,n b =n B –0.01qi,n b' =n B +0.01qi, where i is the imaginary unit, q is the gain-loss factor, and n A is the real part of the refractive index of the first dielectric layer, n B is the real part of the refractive index of the second dielectric layer; the thickness of the first dielectric layer and the second dielectric layer are both 1 / 4 of the optical wavelength corresponding to their respective refractive indices; the loss can be achieved by doping metal ions such as iron ions, and the gain is obtained by nonlinear two-wave mixing. The incident light is a transverse magnetic wave, which is incident vertically from either side of the multilayer dielectric structure;

[0009] When the incident light of a certain wavelength is incident forwardly and backwardly, the zero reflectivity (Exceptional point, EP) point trajectory curve splits. The position of these EP points on the normalized frequency axis is a function of the gain loss factor. Each EP point is the critical point where the photon multilayer switches between the PT symmetric phase and the asymmetric phase. At these critical points of conversion, the reflection coefficient phase A ±π / 2 jump will be generated, which can be used for phase encoding. At the same time, the gain-loss factor or the chemical potential of graphene can be changed to adjust the wavelength of the invisible incident light.

[0010] Furthermore, the first dielectric layer is silicon dioxide, and the second dielectric layer is silicon.

[0011] Furthermore, the thickness of the graphene sheet layer is 0.001 μm.

[0012] Four dielectrics with different refractive indices are stacked layer by layer in a Thue-Morse sequence, so that the refractive index of each layer of dielectric satisfies the condition n(z)=n*(–z) in space, forming a PT-symmetric photon multilayer. The PT symmetry of the structure causes the forward and reverse reflected light waves to be non-reciprocal. This non-reciprocal reflection characteristic causes the trajectory curve of the zero reflectivity point, i.e., EP (Exceptional point), generated by the photon multilayer when incident forward and reversely. At the same time, the reflection coefficient phase At each EP, a ±π / 2 jump will occur, where and They are the reflection coefficient phases corresponding to forward and reverse incidence, respectively. The regular change of this phase in EP provides a good condition for phase modulation encoding. In addition, the position of EP, that is, the position where the phase jump occurs, can be flexibly controlled by adjusting the gain-loss factor, and the width of the phase encoding can be adjusted accordingly to achieve distributed measurement.

[0013] The present invention combines graphene and non-photonic crystals: four dielectric sheets are arranged according to the Thue-Morse sequence rules, and then graphene is embedded in the Thue-Morse sequence photon multilayer that satisfies PT symmetry. The non-reciprocity of the photon multilayer for light wave reflection causes the phase curves of the reflected light to not overlap when the positive and reverse incident light are incident, resulting in the phase of the reflected light Mutations occur in EP, where and They represent the phase of the forward and reverse reflected light, respectively. This regular change in phase can be used for phase modulation encoding. At the same time, by adjusting the gain-loss factor or the chemical potential of graphene, the width of the phase encoding can be changed for distributed measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the Thue-Morse sequence PT symmetric photonic multilayer structure embedded in graphene.

[0015] Figure 2 Thue-Morse sequence TM when not embedded in graphene 4 Electric field intensity distribution of PT-symmetric photonic multilayer structure.

[0016] Figure 3 The middle (a) figure is the reflectivity corresponding to the forward incident light; Figure 3 The middle (b) figure is the reflectivity corresponding to the reverse incident light; Figure 3 Figure (c) shows the relationship between EP and gain-loss factor at forward and reverse incidence.

[0017] Figure 4 The middle figure (a) shows the relationship between the real part of the Hamiltonian eigenvalue and the normalized frequency when the gain-loss factor q = 5; Figure 4 Figure (b) shows the relationship between the imaginary part of the Hamiltonian eigenvalue and the normalized frequency when the gain-loss factor q=5.

[0018] Figure 5 Figure (a) shows the phase when the gain-loss factor q = 5 Relationship with normalized frequency; Figure 5 The middle figure (b) shows the correspondence between the position of the phase jump and the encoding code value when the gain-loss factor q=5.

[0019] Figure 6 is the variation of the phase encoding width with the gain-loss factor and the chemical potential of graphene.

[0020] In the figure, A is the first gain dielectric layer; A' is the first loss dielectric layer; B is the second gain dielectric layer; B' is the second loss dielectric layer. DETAILED DESCRIPTION

[0021] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0022] Here we use S N represents the Thue-Morse sequence numbered N (N = 1, 2, 3, ...), TM N Indicates that the corresponding S N Arranged parity-time symmetric photonic multilayer structure. N contains two uniform dielectrics with different refractive indices, A and B. Mathematically, the iteration rule of the TM sequence is: 1 =A, N = 1; when S N =S N-1(A—>AB, B—>BA), N≥1, where the symbol “—>” means to convert S N-1 In the formula, A and B are replaced by AB and BA respectively to form S N From this we can get S 2 =AB,S 3 =ABBA,S 4 =ABBABAAB, S 5 =ABBABAABBAABABBA,….

[0023] The corresponding parity-time symmetric photon multilayer structure is TM N =S N S' N , where S' N With S N Parity-time symmetry about the origin gives TM 2 =ABB'A',TM 3 =ABBAA'B'B'A',TM 4 =ABBABAABB'A'A'B'A'B'B'A',…. Figure 1 The fourth Thue-Morse sequence S that satisfies PT symmetry is given 4 The photonic multilayer structure is ABBABAABB'A'A'B'A'B'B'A'. The refractive indices of A, A', B and B' are n a =3.53+0.01qi,n a' =3.53-0.01qi, n b =1.46-0.01qi, n b' =1.46+0.01qi. The imaginary part q is the introduced gain-loss factor, indicating gain or loss. When the imaginary part is positive, it indicates the introduction of loss, and when the imaginary part is negative, it indicates the introduction of gain. Loss can be achieved by doping metal ions such as iron ions, and gain is obtained by nonlinear two-wave mixing. The thickness of these four dielectrics is 1 / 4 optical wavelength, that is, the thickness of A and A' is 0.1098μm (μm means micrometer) and 0.2654μm.

[0024] Two graphene sheets with a thickness of 0.001 μm are embedded in the above-mentioned photon multilayer structure. One layer is placed between dielectric layers B and B on the left side of the photon multilayer, and the other layer is placed between B' and B' on the right side. The incident light is a transverse magnetic wave, which enters the photon multilayer vertically. if and I ib I represents the positive and negative vertical incident light waves respectively. Since the PT symmetrical structure has the same transmitted light, the transmitted light waves at positive and negative vertical incidence are both represented by I t express.

[0025] Figure 2 The electric field intensity distribution of the PT-symmetric Thue-Morse sequence photon multilayer when not embedded in graphene is given. The horizontal axis Z-axis is the direction of dielectric layer stacking, which is also the direction of light propagation, and the vertical axis Normalized|E| 2 is the normalized electric field strength. It can be seen that the strongest electric field strength exists near the two positions between the dielectric layers B and B, and B' and B'. Therefore, the present invention places the graphene sheet at these two locations with the strongest electric field strength, which can enhance the third-order nonlinear effect of the structure.

[0026] Figure 3 (a) and (b) show the reflectivity corresponding to the positive and negative incident light. For the convenience of observation, the transmittance and reflectivity are logarithmic in the figure. 0 ) / ω gap represents the normalized angular frequency, where ω=2πc / λ, ω 0 =2πc / λ 0 and ω gap =4ω 0 arcsin│[Re(n a )-Re(n b )] / [Re(n a )+Re(n b )]| 2 / π represent the incident light angular frequency, the incident light center angular frequency and the angular frequency band gap, respectively, c is the speed of light in vacuum, arcsin is the inverse sine function, and Re is the function for extracting the real part of the complex refractive index. The specific position of EP is marked with a white dotted line between the normalized frequency range (-0.12, 0.02) in the parameter space for both the positive and reflected spectra. 1 and EPs 2 .from Figure 3 (c) EPs 1 and EPs 2 Plotted on the same coordinate axis for easy observation, the two intersection points of the two zero reflectivity trajectory lines both fall on the normalized frequency axis, specifically at (ω-ω 0 ) / ω gap =0 and -0.094. The EP trajectory changes with the gain-loss factor and normalized frequency: it first splits from one intersection point and then reconverges at another intersection point. 1 and EPs 2 The parameter space is divided into three parts, marked as I, II, and III in the figure, where I and III are PT symmetric phases and II is non-PT symmetric phase. If the gain-loss factor is set to q = 5, as shown by the dotted line in the figure, then the dotted line is consistent with the two zero reflectivity trajectory points EPs 1There are 4 intersection points with EPs2, that is, 4 EPs are generated. When the normalized frequency gradually increases and the corresponding incident light wavelength decreases, the generated EPs are EP 1 ~EP 4 That is to say, when the normalized frequency gradually increases in the range of (-0.12, 0.02), the photon multilayer is under the action of the reverse incident light at EP 1 It transforms from symmetric phase I to asymmetric phase II, and then under the action of positive incident light, it is transformed into EP 2 It transforms from asymmetric phase II to symmetric phase III, and then under the action of reverse incident light, it is in EP 3 It transforms from symmetric phase III to asymmetric phase II, and finally under the action of positive incident light, it is in EP 4 From asymmetric phase II back to symmetric phase I. This conversion process between PT symmetric phase and asymmetric phase will inevitably cause a jump in the phase of the reflected light, providing the necessary conditions for phase encoding.

[0027] The PT symmetric structure designed by the present invention is a special non-Hermitian structure, and its scattering matrix can be expressed as S = [t, r f ,r b ,t], where t, rf and rb represent the transmission coefficient, the reflection coefficient of forward and reverse incidence respectively. Its eigenvalue and eigenvector are β1,2=t±(rfrb) 1 / 2 and (rf 1 / 2 ,±rb 1 / 2 ). When (rfrb) 1 / 2 = 0, the eigenvalues ​​merge in EP and the eigenvectors degenerate. Therefore, in addition to the important feature of reflectivity being 0, the two eigenvalues ​​β corresponding to EP 1,2 The real part of will produce an anti-crossing, while the imaginary part will produce a crossing. Figure 4 (a) and (b) show the relationship between the real and imaginary parts of the Hamiltonian eigenvalues ​​and the normalized frequency when the gain-loss factor q = 5. 1,2 The intersection of the real part and the imaginary part in Figure (b) show that the positions of the four EPs are EP 1 ~EP 4 , respectively Figure 3 The four EPs in (d) correspond to each other. At the same time, the EP can be calculated 1 ~EP 4 The corresponding normalized frequencies are ω 1～4 =-0.1049, -0.0627, -0.0075 and -0.0056.

[0028] The reflection coefficient of the photon multilayer can be expressed as in and are the complex reflection coefficients r for forward and reverse incidence respectively. f and r b phase. Figure 5 (a) shows the reflection coefficient phase when the gain loss factor q = 5 The change with normalized frequency can also be seen as the wavelength of the incident light gradually decreases from left to right. It can be seen that when the characteristic solution of the scattering matrix S is combined in four EPs, each EP corresponds to a ±π / 2 jump in the reflection coefficient phase. Figure 5 In (b), this set of phase jumps is applied to Q 1 Q 0 Numerical encoding: ω<ω 1 Corresponding to Q 1 Q 0 =00, the system is in Figure 3 (d) PT symmetric phase I; ω 1 <ω<ω 2 Corresponding to Q 1 Q 0 =01, enter asymmetric phase II, ω 2 <ω<ω 3 Corresponding to Q 1 Q 0 =10, transform to PT symmetric phase III, ω 2 <ω<ω 3 Corresponding to Q 1 Q 0 =11, enter asymmetric phase II again, ω>ω 4 Corresponding to Q 1 Q 0 = 00, returning to the asymmetric phase I. This is the main idea of ​​using the photon multilayer designed by the present invention to achieve phase encoding.

[0029] In addition, when the gain loss factor q changes, Figure 3 The intersection position of the dotted line and in (d) will also change, that is, the corresponding normalized frequency of each EP point changes. Figure 6 The width of phase encoding is compared when the gain loss factor is different. If the graphene chemical potential μ is kept constant c = 0eV. When the gain loss factor q increases from 5 to 6, the widths of codes 01 and 11 increase, while the width of code 10 decreases. On the other hand, when the graphene chemical potential μ c When changes, Figure 3 (d) EPs representing zero reflectivity 1 and EPs 2The shape of the curve will change. If the gain loss factor q = 5 is kept unchanged, when the graphene chemical potential increases from 0eV to 0.2eV, the width of the codes 00 and 10 increases, while the width of the code 01 decreases. This shows that by changing the gain loss factor or the chemical potential of graphene, the width of the phase encoding can be flexibly adjusted to achieve distributed measurement.

[0030] In summary, the forward and reverse reflected light waves of the photon multilayer that follows the Thue-Morse sequence and satisfies the PT symmetry are non-reciprocal, and the trajectory curves of the zero reflectivity (EP) points generated during forward and reverse incidence are split. The positions of these EPs on the normalized frequency axis are functions of the gain loss factor, and each EP is the critical point where the photon multilayer transforms between the PT symmetric phase and the asymmetric phase. At these critical points of transformation, the reflection coefficient phase A ±π / 2 jump will be generated, which can be used for phase encoding. At the same time, the width of phase encoding can be flexibly controlled by adjusting the gain-loss factor to achieve distributed measurement. This effect can be used to make optical fiber sensors.

[0031] This can be implemented as follows:

[0032] (1) Material selection. Two dielectrics with substrates of silicon dioxide and silicon were selected, and gain or loss was introduced by doping or nonlinear two-wave mixing to form four dielectrics A, A', B and B', whose refractive indices were 3.53+0.01qi, 1.46-0.01qi, 3.53-0.01qi and 1.46+0.01qi, respectively, where q is the gain-loss factor, and gain and loss are introduced by doping or nonlinear two-wave mixing, respectively.

[0033] (2) Structural design. These four dielectrics are numbered according to the Thue-Morse sequence and different sequence numbers are selected. N , stacked into a photon multilayer that conforms to parity-time symmetry, such as the photon multilayer when N = 4 is TM 4 =ABBABAABB'A'A'B'A'B'B'A', and then two graphene sheets with a thickness of 0.001 μm are embedded between B, B and B', B' respectively (such as Figure 1 ).

[0034] (3) Detecting the reflection coefficient phase The gain-loss factor q = 5 is selected to change the wavelength of the incident light, that is, to change the frequency ω of the incident light within the normalized frequency range of (-0.12, 0.02). First, the incident light is incident vertically into the photon multilayer from the forward direction. 2 =-0.0627 and ω 3 =-0.0075 Two positions detected Phase jumps of -π / 2 and π / 2 appear respectively. Then the incident light enters the photon multilayer from the reverse vertical incidence, and at ω 1 = -0.1049 and ω 4 =-0.0056 Two positions detected There is a phase jump of π / 2 (such as Figure 3-5 ).

[0035] (4) Apply phase jump to numerical coding. Combine the above two sets of phase jumps and apply them to Q 1 Q 0 Numerical encoding: ω<ω 1 Corresponding to Q 1 Q 0 =00,ω 1 <ω<ω 2 Corresponding to Q 1 Q 0 =01,ω 2 <ω<ω 3 Corresponding to Q 1 Q 0 =10,ω 2 <ω<ω 3 Corresponding to Q 1 Q 0 =11,ω>ω 4 Corresponding to Q 1 Q 0 =00(such as Figure 5 ).

[0036] Adjusting the gain-loss factor changes the phase encoding width. Adjusting the gain-loss factor of the dielectric can adjust the normalized frequency position of EP on the reflection spectrum, thereby controlling the width of the phase encoding and achieving distributed measurement. For example, when q is increased from 5 to 6, Figure 3 The dotted line representing the gain-loss factor in (c) moves to the right, resulting in a corresponding change in the phase encoding width: the widths of codes 01 and 11 increase, while the width of code 10 decreases. Figure 6 ).

[0037] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

[0038] Although the terms such as ...1, ...2, etc. are used more frequently in this article, the possibility of using other terms is not excluded. These terms are used only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional restrictions is contrary to the spirit of the present invention.

Claims

1. A non-periodic photonic multilayer structure that can be used for phase modulation coding, characterized in that: The non-periodic photon multilayer structure comprises two Thue-Morse sequences with parity-time symmetric distribution, wherein the Thue-Morse sequence S N The iteration rule is: when N = 1, S1 = A, when N ≥ 2, S N-1 The A in is replaced by AB, S N-1 The B in the equation is replaced by BA to obtain S. N , A is the first dielectric layer; B is the second dielectric layer; wherein the subscript N is the ordinal number of the sequence, the first dielectric layer and the second dielectric layer are two uniform dielectric sheets with different refractive indices, and there are also two graphene sheet layers in the Thue-Morse sequence, and the graphene sheet layers are respectively embedded between two adjacent second dielectric layers; The first dielectric layer located on one side of the symmetry center of the non-periodic photonic multilayer structure is called the first lossy dielectric layer, and its refractive index in the light-transmitting state is expressed as n a The first dielectric layer located on the other side of the symmetry center of the non-periodic photon multilayer structure is called the first gain dielectric layer, and its refractive index in the light-transmitting state is expressed as n a' The second dielectric layer on the same side as the first gain dielectric layer is called the second gain dielectric layer, and its refractive index in the light-transmitting state is expressed as n b The second dielectric layer on the same side as the first lossy dielectric layer is called the second lossy dielectric layer, and its refractive index in the light-transmitting state is represented by n b' ; <h2 style=";text-align:left;direction:ltr">n<h2 style=";text-align:left;direction:ltr"> a <h2 style=";text-align:left;direction:ltr"> =n<h2 style=";text-align:left;direction:ltr"> A <h2 style=";text-align:left;direction:ltr"> +0.01qi,n<h2 style=";text-align:left;direction:ltr"> a' <h2 style=";text-align:left;direction:ltr"> =n<h2 style=";text-align:left;direction:ltr"> A <h2 style=";text-align:left;direction:ltr"> -0.01qi,n<h2 style=";text-align:left;direction:ltr"> b <h2 style=";text-align:left;direction:ltr"> =n<h2 style=";text-align:left;direction:ltr"> B <h2 style=";text-align:left;direction:ltr"> -0.01qi,n<h2 style=";text-align:left;direction:ltr"> b' <h2 style=";text-align:left;direction:ltr"> =n<h2 style=";text-align:left;direction:ltr"> B <h2 style=";text-align:left;direction:ltr"> +0.01qi, where i is the imaginary unit, q is the gain-loss factor, and n A is the real part of the refractive index of the first dielectric layer, n B is the real part of the refractive index of the second dielectric layer; the thickness of the first dielectric layer and the second dielectric layer are both 1 / 4 of the optical wavelength corresponding to their respective refractive indices; the loss is achieved by doping iron ions, and the gain is obtained by nonlinear two-wave mixing. The incident light is a transverse magnetic wave, which is incident vertically from either side of the multilayer dielectric structure; When the incident light of a certain wavelength is incident forwardly and backwardly, the trajectory curve of the zero reflectivity point splits. The position of these zero reflectivity points on the normalized frequency axis is a function of the gain loss factor. Each zero reflectivity point is the critical point where the photon multilayer switches between the PT symmetric phase and the asymmetric phase. At these critical points of conversion, the reflection coefficient phase (φrf+φrb) / 2 will produce a jump of ±π / 2, which is used for phase encoding, where r f and r b Denote the complex reflection coefficients of forward and reverse incidence respectively, φrf and φrb denote the phase of the complex reflection coefficient of forward incidence and the phase of the complex reflection coefficient of reverse incidence respectively; at the same time, the gain-loss factor or the chemical potential of graphene can be changed to achieve the wavelength adjustment of the invisible incident light.

2. The non-periodic photonic multilayer structure for phase modulation coding according to claim 1, characterized in that: The first dielectric layer is silicon dioxide, and the second dielectric layer is silicon.

3. A non-periodic photonic multilayer structure for phase modulation coding according to claim 1 or 2, characterized in that: The thickness of the graphene sheet layer is 0.001 μm.

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