Transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector and construction method thereof

Abstract

The invention discloses a conversion optical cascade one-dimensional photonic crystal broadband omnidirectional reflector and a construction method thereof, and belongs to the technical field of optics. The method comprises the following steps: constructing an original one-dimensional photonic crystal omnidirectional reflector by using a medium Ai and a medium Bi; the method comprises the following steps: cascading a plurality of single-stage structures made of the same material, and constructing an original cascaded one-dimensional photonic crystal omnidirectional reflector; determining a compression coefficient a; according to the characteristic parameters of the medium Ai and the medium Bi and a, calculating the characteristic parameters of a medium A'i and a medium B'i required by the conversion optical cascade one-dimensional photonic crystal broadband omnidirectional reflector; materials of a medium A'i and a medium B'i are determined according to characteristic parameters of the medium A'i and the medium B'i, the medium A'i and the medium B'i are utilized to construct the conversion optical cascade one-dimensional photonic crystal broadband omnidirectional reflector, and compared with an original cascade one-dimensional photonic crystal omnidirectional reflector, the conversion optical cascade one-dimensional photonic crystal broadband omnidirectional reflector has the advantages that the omnidirectional reflection bandwidth is increased, and the thickness is reduced at the same time. While the optical performance of the optical system is improved, the miniaturization and integration of the system are realized.

Description

Technical Field

[0001] The invention belongs to the field of optical technology, and in particular relates to a transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector and a construction method thereof. Background Art

[0002] One-dimensional photonic crystal omnidirectional reflectors are composed of periodic multilayer dielectrics. They are simple to manufacture and low in cost. Therefore, they have broad application prospects in the fields of optical fiber, waveguide, and thermal radiation. Reflectors are a commonly used optical component. Currently, the commonly used reflectors are mainly metal and multilayer dielectric. Compared with metal and multilayer dielectric reflectors, one-dimensional photonic crystal omnidirectional reflectors have extremely low reflection loss and selectable omnidirectional reflection bandwidth.

[0003] In recent years, researchers have conducted a lot of research on how to expand the width of the omnidirectional reflection band. Common methods include: (1) increasing the ratio of the refractive indices of the two media that make up the photonic crystal. In the visible light band, since there is an upper limit to the refractive index of the material, the method of expanding the omnidirectional reflection bandwidth by increasing the refractive index ratio of the material has certain limitations; (2) cascading multiple one-dimensional photonic crystal structures with different omnidirectional reflection bands. This frequency domain superposition is a commonly used method in thin film optics, that is, superimposing two or more one-dimensional photonic crystal structures with different omnidirectional reflection center frequencies. The omnidirectional reflection band formed by the cascaded structure is the superposition of the omnidirectional reflection bands of each one-dimensional photonic crystal structure. However, this cascade structure will lead to an increase in the size of the reflector, which is inconsistent with the integration and miniaturization of the optical path. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector and a construction method thereof, which solves the problems in the prior art.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] The method for constructing a transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector comprises the following steps:

[0007] Using medium A i and medium B i Constructing a primitive one-dimensional photonic crystal omnidirectional reflector;

[0008] Cascading multiple single-stage structures of the same material to construct an original cascaded one-dimensional photonic crystal omnidirectional reflector;

[0009] Determine the compression factor a;

[0010] According to medium A i and medium B iThe characteristic parameters and compression coefficient a of the medium A' required to form the transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector are calculated. i and medium B' i Characteristic parameters of

[0011] According to medium A' i and medium B' i Characteristic parameters of medium A' i and medium B' i Materials, using medium A' i and medium B' i Constructing a transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector.

[0012] Furthermore, the medium A i The dielectric constant of medium B is different from that of medium B. i The dielectric constant of .

[0013] Furthermore, the arrangement structure of the original cascaded one-dimensional photonic crystal omnidirectional reflector is expressed as:

[0014] (A1B1) N (A2B2) N (A3B3) N

[0015] Where N is the medium A i and medium B i The number of overlaps, and N ≥ 5; medium A i and medium B i The optical thickness is 0.25λ0, where λ0 is the central working wavelength of the original one-dimensional photonic crystal omnidirectional reflector.

[0016] Furthermore, the calculation formula of the compression coefficient a is:

[0017]

[0018] Wherein, L is the thickness of the original cascaded one-dimensional photonic crystal omnidirectional reflector, and L' is the desired thickness of the constructed one-dimensional transformed photonic crystal omnidirectional reflector.

[0019] Furthermore, the medium A' i and medium B' i The calculation process of the characteristic parameters is:

[0020] 1) The original cascaded one-dimensional photonic crystal omnidirectional reflector structure is measured using the original coordinate system (x, y, z), and the transformed cascaded one-dimensional photonic crystal omnidirectional reflector structure is measured using the transformed coordinate system (x', y', z'). The cascaded one-dimensional photonic crystal structure is subjected to a longitudinal spatial compression transformation, and the transformation formula can be expressed as:

[0021]

[0022] Among them, the compression coefficient a determines the thickness of the transformation cascade one-dimensional photonic crystal omnidirectional reflector; using formula (1), the corresponding Jacobian matrix is ​​obtained:

[0023]

[0024] 2) Using the principle of transformation optics, the dielectric constant and magnetic permeability of the two overlapping materials are calculated twice:

[0025]

[0026] Among them, ε is the dielectric constant of the original dielectric layer material, which is composed of dielectric A i The refractive index n A and medium B i The refractive index n B Derived; μ represents the magnetic permeability of the original dielectric layer material; ε' and μ' are the dielectric constant and magnetic permeability of the medium after optical transformation, respectively;

[0027] 3) Assuming that the incident wave is a TM wave, the dielectric constant and permeability given by formula (3) are demagnetized:

[0028]

[0029] in, is the dielectric constant of the medium after non-magnetization treatment, ε x , ε y , ε z Represent the components of ε on the x, y, and z axes respectively.

[0030] Furthermore, medium A i and medium B i They are titanium dioxide and silicon dioxide respectively.

[0031] The transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector is constructed using the above construction method.

[0032] The construction system of transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector includes:

[0033] Original one-dimensional photonic crystal omnidirectional reflector building block: using medium A i and medium B i Constructing a primitive one-dimensional photonic crystal omnidirectional reflector;

[0034] Cascade module: Cascade multiple single-stage structures of the same material to construct an original cascaded one-dimensional photonic crystal omnidirectional reflector;

[0035] Compression coefficient determination module: determine the compression coefficient a;

[0036] Characteristic parameter calculation module: According to medium A i and medium B i The characteristic parameters and compression coefficient a of the medium A' required to form the transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector are calculated. i and medium B' i Characteristic parameters of

[0037] And, transformation optics cascade one-dimensional photonic crystal broadband omnidirectional reflector building block: according to the medium A' i and medium B' i Characteristic parameters of medium A' i and medium B' i Materials, using medium A' i and medium B' i Constructing a transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector.

[0038] The above-mentioned transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector is used in the preparation of photonic integrated circuits.

[0039] The above-mentioned transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector is used in the preparation of optical sensors.

[0040] Beneficial effects of the present invention:

[0041] The present invention calculates the dielectric constant and magnetic permeability of the required medium according to the omnidirectional reflection coefficient of the original cascade one-dimensional photonic crystal omnidirectional reflector and the required compression coefficient, and constructs a one-dimensional transformation optical cascade photonic crystal omnidirectional reflector. Compared with the original cascade one-dimensional photonic crystal omnidirectional reflector, the transformation optical cascade one-dimensional photonic crystal structure has the advantages of simultaneously increasing the omnidirectional reflection bandwidth and reducing the thickness, while improving the optical performance of the optical system, and realizing system miniaturization and integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0043] Figure 1 It is a structural diagram of the original cascaded one-dimensional photonic crystal omnidirectional reflector of the present invention;

[0044] Figure 2 It is a structural diagram of the compressed one-dimensional transformation photonic crystal omnidirectional reflector of the present invention;

[0045] Figure 3 is a bandgap diagram of the original single-stage one-dimensional photonic crystal omnidirectional reflector of the present invention;

[0046] Figure 4 It is a reflection spectrum diagram of the original cascaded one-dimensional photonic crystal omnidirectional reflector of the present invention;

[0047] Figure 5 is a bandgap diagram of the original cascaded one-dimensional photonic crystal omnidirectional reflector of the present invention;

[0048] Figure 6 It is a bandgap diagram of the cascaded one-dimensional transformation photonic crystal omnidirectional reflector with different transformation coefficients of the present invention. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] Example 1

[0051] The method for constructing a transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector comprises the following steps:

[0052] S1, using medium A i and medium B i Construct an original one-dimensional photonic crystal omnidirectional reflector, where medium A i The dielectric constant of medium B is different from that of medium B. i The dielectric constant of

[0053] S2, calculate the omnidirectional reflection bandwidth of each single-stage one-dimensional photonic crystal structure respectively;

[0054] The omnidirectional reflection bandwidth of a single-stage one-dimensional photonic crystal structure can be calculated using formula (6) to formula (8) in Example 2.

[0055] S3, cascade multiple single-stage structures of the same material to construct an original cascade one-dimensional photonic crystal omnidirectional reflector, and the arrangement structure is represented by (A1B1) N (A2B2) N (A3B3) N , N is medium A i and medium B i The number of overlaps;

[0056] Where N≥5, medium A i and medium B iThe optical thickness is 0.25λ0, where λ0 is the central working wavelength of the original one-dimensional photonic crystal omnidirectional reflector.

[0057] S4, calculating the omnidirectional reflection coefficient of the original cascaded one-dimensional photonic crystal omnidirectional reflector by using the transfer matrix method, and calculating the omnidirectional reflection bandwidth of the original cascade structure;

[0058] Similarly, the omnidirectional reflection bandwidth of the original cascade structure can be calculated using formula (6)-formula (8) in Example 2.

[0059] By comparing the calculated omnidirectional reflection bandwidth of the original cascade structure with the omnidirectional reflection bandwidth of the single-stage one-dimensional photonic crystal structure calculated in S2, it can be found that the bandwidth range becomes larger after cascading.

[0060] S5, determining the compression coefficient a;

[0061] The compression coefficient a is determined by calculation or setting. If it is determined by calculation, the calculation formula is:

[0062]

[0063] Wherein, L is the thickness of the original one-dimensional photonic crystal omnidirectional reflector, and L' is the desired thickness of the constructed one-dimensional transformed photonic crystal omnidirectional reflector;

[0064] S6, according to medium A i and medium B i The characteristic parameters of and the compression coefficient a in S5 are used to calculate the characteristic parameters of medium A'i and medium B'i required to constitute the transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector;

[0065] The characteristic parameters include dielectric constant and magnetic permeability. The calculation process of the characteristic parameters of medium A'i and medium B'i is:

[0066] 1) In order to make the transformed cascaded one-dimensional photonic crystal omnidirectional reflection bandwidth consistent, it is necessary to use the principle of transformation optics to perform secondary electromagnetic calculations; specifically, assuming that the original cascaded one-dimensional photonic crystal omnidirectional reflection mirror structure is measured using the original coordinate system (x, y, z), and the transformed cascaded one-dimensional photonic crystal omnidirectional reflection mirror structure is measured using the transformed coordinate system (x', y', z'), the cascaded one-dimensional photonic crystal structure is subjected to longitudinal spatial compression transformation, and the transformation formula can be expressed as:

[0067]

[0068] Among them, the compression coefficient a determines the thickness of the transformation cascade one-dimensional photonic crystal omnidirectional reflector; using formula (1), the corresponding Jacobian matrix can be obtained:

[0069]

[0070] 2) Using the principle of transformation optics, in order to keep the optical properties of the transformation cascade one-dimensional photonic crystal omnidirectional reflector unchanged, it is necessary to perform a secondary calculation of the dielectric constant and magnetic permeability of the two overlapping materials:

[0071]

[0072] Where ε is the dielectric constant of the original dielectric layer material, which is respectively determined by the refractive index n of the medium Ai A and the refractive index n of the medium Bi B Derived; μ represents the magnetic permeability of the original dielectric layer material, which is generally equivalent to the magnetic permeability μ0 of free space; ε' and μ' are the dielectric constant and magnetic permeability of the medium after optical transformation, respectively;

[0073] The material of the transformed cascaded one-dimensional photonic crystal omnidirectional reflector is in tensor form, and its magnetic permeability changes from non-magnetic to magnetic; then, in the optical band, most natural materials do not have magnetism;

[0074] 3) Assuming that the incident wave is a TM wave, the dielectric constant and magnetic permeability given by equation (3) are demagnetized:

[0075]

[0076] During the non-magnetic treatment process, the equivalent refractive index of the transformation medium material is kept unchanged; according to optical principles, the omnidirectional reflection coefficient of the above-mentioned one-dimensional transformation photonic crystal omnidirectional reflector is the same as the omnidirectional reflection coefficient of the original one-dimensional photonic crystal omnidirectional reflector.

[0077] S7, according to the characteristic parameters of medium A'i and medium B'i calculated in S6, determine the i and medium B' i Materials, using medium A' i and medium B' i Construct a transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector, the arrangement structure is represented by (A'1B'1) N (A'2B'2) N (A'3B'3) N .

[0078] Example 2

[0079] like Figure 1 This is the structural diagram of the original cascaded one-dimensional photonic crystal omnidirectional reflector. Figure 2 This is a structural diagram of a one-dimensional transformation photonic crystal cascade omnidirectional reflector. For photonic crystals, the greater the difference in the relative dielectric constants of the two layers of media, the wider the photonic band gap can be obtained;

[0080] In this embodiment, three single-stage photonic crystal structures with omnidirectional reflection characteristics are designed. The three single-stage photonic crystal structures are all composed of two identical dielectric material layers overlapping each other, and the overlapping period is 12. Among them, the first dielectric material is titanium dioxide (TiO2), denoted as A i The second dielectric material is silicon dioxide (SiO2), denoted as B i In the visible light frequency range, the refractive indices of titanium dioxide and silicon dioxide are n A =2.43 and n B =1.46. The one-dimensional photonic crystal omnidirectional reflector structure can adopt a λ0 / 4 film system, that is, the thickness of the single-layer medium satisfies: n A d A =n B d B =λ0 / 4. In order to form a wider omnidirectional reflector in the visible light band, the central working wavelength of the second cascaded one-dimensional photonic crystal omnidirectional reflector is designed to be 540nm. Therefore, the physical thicknesses of the two materials calculated are: d A2 =92.5nm, d B2 =55.5nm. The physical thickness of the two materials of the first and third cascaded one-dimensional photonic crystal omnidirectional reflectors are obtained by increasing and decreasing 5nm on the basis of the second omnidirectional reflector, that is: d A1 =87.5nm, d B1 =50.5nm, d A3 =97.5nm, d B3 =60.5nm. Three single-stage one-dimensional photonic crystal omnidirectional reflectors are cascaded in sequence to form a 3-cascade one-dimensional photonic crystal omnidirectional reflector model: (A1B1) 12 (A2B2) 12 (A3B3) 12 ,like Figure 1 In order to reduce the thickness of the designed three-stage cascade one-dimensional photonic crystal omnidirectional reflector structure, a spatial compression transformation is performed on it, and the resulting transformed three-stage cascade one-dimensional photonic crystal omnidirectional reflector structure is recorded as: (A'1B'1) 12 (A'2B'2) 12 (A'3B'3) 12 ,like Figure 2 As shown. Among them, the spatial transformation coefficient is defined as L and L' are the thicknesses of the original three-stage cascaded one-dimensional photonic crystal omnidirectional reflector structure and the transformed three-stage cascaded one-dimensional photonic crystal omnidirectional reflector structure, respectively.

[0081] For the original cascaded one-dimensional photonic crystal omnidirectional reflector structure, the transmission matrix method can be used to calculate the omnidirectional reflection characteristics. For TM wave incidence, assuming the incident angle is θ, the electric field E and magnetic field H on the two boundaries of any layer of the original cascaded one-dimensional photonic crystal medium satisfy the relationship:

[0082]

[0083] Where ω is the angular frequency, k l is the intrinsic wave number or propagation constant of the constituent material d l is the thickness of the lth layer of medium, μ l is the magnetic permeability of the medium, ε l is the dielectric constant of the medium, and each layer of the medium is non-magnetic, that is, μ l =μ0, μ0 is the magnetic permeability of vacuum;

[0084] According to the continuity condition of the tangential electric field, the total transmission matrix of the cascaded one-dimensional photonic crystal structure can be expressed as:

[0085]

[0086] Where P is the total number of dielectric layers in the cascaded photonic crystal, x 11 、x 12 、x 21 、x 22 Respectively represent each element of the cascade matrix;

[0087] Assume that the cascaded one-dimensional photonic crystal structure omnidirectional reflector is placed in free space, that is, the incident space and the exit space are both air, and its dielectric constant and magnetic permeability are represented by ε0 and μ0. According to the definition of reflection coefficient, using equations (5) and (6), the expression of reflection coefficient R(ω) is obtained as follows:

[0088]

[0089] Among them, E1 (-) (0), E1 (+) (0) are the electric field intensity of the electromagnetic wave reflected from the incident interface and the electric field intensity of the electromagnetic wave emitted from the incident interface respectively;

[0090] Further, the reflectivity of the cascaded photonic crystal is expressed as:

[0091] r=|R(ω)| 2 (8)

[0092] For the transformation cascade one-dimensional photonic crystal omnidirectional reflector structure, since the constituent materials are in tensor form, the electromagnetic commercial software HFSS was used for full-wave calculation.

[0093] The omnidirectional reflection characteristics of a single-stage one-dimensional photonic crystal are as follows: Figure 3 As shown in (a)-(d) in the figure, the omnidirectional reflection bandwidth range of the first cascaded one-dimensional photonic crystal is 433-453nm; the omnidirectional reflection bandwidth range of the second cascaded one-dimensional photonic crystal is 466-488nm; and the omnidirectional reflection bandwidth range of the third cascaded one-dimensional photonic crystal is 499-524nm.

[0094] The calculation results show that as the physical thickness of the dielectric layer gradually increases, the omnidirectional reflection band range of the one-dimensional photonic crystal will move toward the low frequency band. This phenomenon is attributed to the fact that as the physical thickness of the dielectric layer increases, the central wavelength of the Bragg diffraction of the one-dimensional photonic crystal shifts toward the high frequency, thereby causing the omnidirectional reflection band of the one-dimensional photonic crystal to shift toward the low frequency band.

[0095] like Figure 4 As shown in , the reflectivity of the cascaded one-dimensional photonic crystal structure is calculated when the TM wave is incident at any angle. By selecting the reflection coefficient of the TM wave at 0° and 85° as the boundary, the omnidirectional reflection band gap of the cascaded one-dimensional photonic crystal structure can be obtained. Figure 5 As shown, it can be seen that the omnidirectional reflection bandwidth range of the cascaded one-dimensional photonic crystal structure is 446-494nm, and the omnidirectional reflection bandwidth reaches 48nm, which is equivalent to the superposition of the omnidirectional reflection bandwidth range of three single-stage one-dimensional photonic crystal structures.

[0096] In order to make the transformed three-stage cascade one-dimensional photonic crystal omnidirectional reflector bandwidth consistent, it is necessary to use the principle of transformation optics to perform a secondary calculation of its electromagnetic. Specifically, it is assumed that the original three-stage cascade one-dimensional photonic crystal omnidirectional reflector structure is measured using the original coordinate system (x, y, z), and the transformed three-stage cascade one-dimensional photonic crystal omnidirectional reflector structure is measured using the transformed coordinate system (x', y', z'), respectively. Figure 1 and Figure 2 As shown. Since only the longitudinal space compression transformation is performed on the three-level cascaded one-dimensional photonic crystal structure, the transformation formula can be expressed as:

[0097]

[0098] Among them, the transformation coefficient a determines the thickness of the three-stage cascaded one-dimensional photonic crystal omnidirectional reflector. Using formula (1), the corresponding Jacobian matrix can be obtained:

[0099]

[0100] Using the principle of transformation optics, in order to keep the optical properties of the three-stage cascaded one-dimensional photonic crystal omnidirectional reflector unchanged, it is necessary to perform a secondary calculation of the dielectric constant and magnetic permeability of the two overlapping materials:

[0101]

[0102] Where ε is the dielectric constant of the original dielectric layer material, which is given by n A and n B Derived; μ represents the magnetic permeability of the original dielectric layer material, which is generally equivalent to the magnetic permeability μ0 of free space. It can be seen that when the material of the three-stage cascaded one-dimensional photonic crystal omnidirectional reflector is transformed into a tensor form, its magnetic permeability changes from non-magnetic to magnetic. Then, in the optical band, most natural materials do not have magnetism. Therefore, assuming that the incident wave is a TM wave, the dielectric constant and magnetic permeability given by equation (3) are non-magnetized:

[0103]

[0104] During the non-magnetic treatment process, the equivalent refractive index of the transformation medium material is kept unchanged. It can be seen from formula (4) that the constituent materials of the transformation cascade structure have uniaxial crystal characteristics, which can generally be achieved by selecting suitable natural crystals or using artificial multilayer material structures. In addition, it can be seen from formula (4) that the original cascade photonic crystal can be spatially compressed to any value. Then, the reflection characteristics of the transformation cascade one-dimensional photonic crystal structure were numerically simulated using commercial electromagnetic simulation software.

[0105] In order to verify the invariance of the optical properties of the transformation cascade one-dimensional photonic crystal structure, a variety of transformation coefficients of the transformation cascade one-dimensional photonic crystal structure were selected for electromagnetic simulation. The three-dimensional structure of the transformation cascade one-dimensional photonic crystal structure was modeled using commercial electromagnetic simulation software, using Floquet ports and open boundary conditions in the vertical direction and periodic boundary conditions in the horizontal direction, so that it can be equivalent to a one-dimensional photonic crystal structure.

[0106] Figure 6 (a)-(d) in the figure respectively show the reflectivity of the transformed cascaded one-dimensional photonic crystal structure with transformation coefficients of 1, 0.8, 0.5 and 0.1, and compare them with the reflectivity of the original cascaded one-dimensional photonic crystal. Among them, the electromagnetic parameters of the transformed cascaded one-dimensional photonic crystal structure use magnetic material parameters and non-magnetic material parameters, which are given by equations (3) and (4) respectively. Figure 5 It can be seen that no matter how large the transformation coefficient is, the reflectivity of the transformation cascade one-dimensional photonic crystal structure is consistent with the reflectivity of the original cascade one-dimensional photonic crystal. The reflectivity of the transformation cascade one-dimensional photonic crystal structure after non-magnetic treatment has a certain error outside the omnidirectional reflection band, and has no effect on the omnidirectional reflection band.

[0107] The transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector constructed by the present invention is composed of periodic multilayer dielectrics and has the characteristics of simple production and low cost, so it has broad application prospects in the fields of optical fiber, waveguide and thermal radiation. Compared with metal and multilayer dielectric reflectors, the advantages of one-dimensional photonic crystal omnidirectional reflectors are extremely low loss, selective design and adjustment of omnidirectional reflection bandwidth, etc. The combination of transformation optical technology and photonic crystals can be used in the fields of stealth and optical camouflage. By manipulating the propagation path of light, the target object can be made "invisible" or reduced in visibility, and it can be applied to the military and security fields.

[0108] The introduction of photonic crystal omnidirectional reflectors can enhance the optical signal manipulation capability in photonic integrated circuits and can be used for light regulation and separation in waveguides. In addition, the transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector of the present invention can also be used in the design of highly sensitive optical sensors, which can be applied to the fields of environmental monitoring, biological detection, etc., to enhance the reflection of optical signals to improve detection accuracy.

[0109] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0110] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for constructing a transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector, characterized in that: The following steps are involved: Using medium A i and medium B i Constructing a primitive one-dimensional photonic crystal omnidirectional reflector; Cascading multiple single-stage structures of the same material to construct an original cascaded one-dimensional photonic crystal omnidirectional reflector; Determine the compression factor a; According to medium A i and medium B i The characteristic parameters and compression coefficient a of the medium A' required to form the transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector are calculated. i and medium B' i Characteristic parameters of According to medium A' i and medium B' i Characteristic parameters of medium A' i and medium B' i Materials, using medium A' i and medium B' i Constructing a transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector.

2. The method for constructing a transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector according to claim 1, characterized in that: The medium A i The dielectric constant of medium B is different from that of medium B. i The dielectric constant of .

3. The method for constructing a transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector according to claim 1, characterized in that: The arrangement structure of the original cascaded one-dimensional photonic crystal omnidirectional reflector is expressed as: <h2 style=";text-align:left;direction:ltr">(A1B1)<h2 style=";text-align:left;direction:ltr"> N <h2 style=";text-align:left;direction:ltr"> (A2B2)<h2 style=";text-align:left;direction:ltr"> N <h2 style=";text-align:left;direction:ltr"> (A3B3)<h2 style=";text-align:left;direction:ltr"> N Where N is the medium A i and medium B i The number of overlaps, and N ≥ 5; medium A i and medium B i The optical thickness is 0.25λ0, where λ0 is the central working wavelength of the original one-dimensional photonic crystal omnidirectional reflector.

4. The method for constructing a transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector according to claim 1, characterized in that: The calculation formula of the compression coefficient a is: Wherein, L is the thickness of the original cascaded one-dimensional photonic crystal omnidirectional reflector, and L' is the desired thickness of the constructed one-dimensional transformed photonic crystal omnidirectional reflector.

5. The method for constructing a transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector according to claim 1, characterized in that: The medium A' i and medium B' i The calculation process of the characteristic parameters is: 1) The original cascaded one-dimensional photonic crystal omnidirectional reflector structure is measured using the original coordinate system (x, y, z), and the transformed cascaded one-dimensional photonic crystal omnidirectional reflector structure is measured using the transformed coordinate system (x', y', z'). The cascaded one-dimensional photonic crystal structure is subjected to a longitudinal spatial compression transformation, and the transformation formula can be expressed as: Among them, the compression coefficient a determines the thickness of the transformation cascade one-dimensional photonic crystal omnidirectional reflector; using formula (1), the corresponding Jacobian matrix is ​​obtained: 2) Using the principle of transformation optics, the dielectric constant and magnetic permeability of the two overlapping materials are calculated twice: Among them, ε is the dielectric constant of the original dielectric layer material, which is composed of dielectric A i The refractive index n A and medium B i The refractive index n B Derived; μ represents the magnetic permeability of the original dielectric layer material; ε' and μ' are the dielectric constant and magnetic permeability of the medium after optical transformation, respectively; 3) Assuming that the incident wave is a TM wave, the dielectric constant and permeability given by formula (3) are demagnetized: in, is the dielectric constant after the medium is demagnetized, ε x , ε y , ε z Represent the components of ε on the x, y, and z axes respectively.

6. The method for constructing a transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector according to claim 1, wherein the medium A i and medium B i They are titanium dioxide and silicon dioxide respectively.

7. A transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector, constructed by the construction method described in any one of claims 1 to 6.

8. A system for constructing a transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector, characterized in that: include: Original one-dimensional photonic crystal omnidirectional reflector building block: using medium A i and medium B i Constructing a primitive one-dimensional photonic crystal omnidirectional reflector; Cascade module: Cascade multiple single-stage structures of the same material to construct an original cascaded one-dimensional photonic crystal omnidirectional reflector; Compression coefficient determination module: determine the compression coefficient a; Characteristic parameter calculation module: According to medium A i and medium B i The characteristic parameters and compression coefficient a of the medium A' required to form the transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector are calculated. i and medium B' i Characteristic parameters of And, transformation optics cascade one-dimensional photonic crystal broadband omnidirectional reflector building block: according to the medium A' i and medium B' i Characteristic parameters of medium A' i and medium B' i Materials, using medium A' i and medium B' i Constructing a transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector.

9. Use of the transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector according to claim 7 in the preparation of photonic integrated circuits.

10. Use of the transformation optical cascade one-dimensional photonic crystal broadband omnidirectional reflector according to claim 7 in the preparation of optical sensors.

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