A unidirectional plasmonic Bragg waveguide reflector

Abstract

A unidirectional plasmonic Bragg waveguide reflector includes a first metal layer, a non-metal layer, and a second metal layer; the non-metal layer includes a core layer and at least one microstructure formed on the core layer and integrally formed with the core layer, which is asymmetric along the direction of electromagnetic wave transmission in the core layer; when the electromagnetic wave is incident along the first direction of the reflector, the reflector exhibits a high absorption rate; when the electromagnetic wave is incident along the second direction of the reflector, the reflector exhibits a high reflectivity. This reflector can achieve unidirectional reflection of electromagnetic waves, that is, this reflector can simultaneously realize the functions of a single-direction reflector and a single-direction absorber.

Description

Technical Field

[0001] The present invention relates to a plasmonic Bragg waveguide, and more particularly to a unidirectional plasmonic Bragg waveguide reflector. Background Art

[0002] Plasmons provide an effective way to focus or guide light beyond the diffraction limit. Among various plasmonic optical waveguides, metal-insulator-metal (MIM) waveguides have attracted much attention because of their very strong field confinement and can be used for plasmonic circuits on highly integrated chips. Nowadays, a series of plasmonic devices based on MIM waveguides have been proposed, such as detectors, reflectors, electro-optic switches, nonlinear devices, filters, resonators, etc. In recent years, among many MIM waveguide devices, the attention paid to plasmonic Bragg reflectors has increased significantly. This is because plasmonic Bragg reflectors can be used to control plasmonic modules, which are the basic units for forming plasmonic devices and plasmonic circuits. However, the nanostructure units in the prior art and even the entire structure of the plasmonic Bragg reflector are restricted to be longitudinally symmetric structures. Therefore, the reflectivity of light incident from the left side of the plasmonic module is always equal to that incident from the right side of the plasmonic module. However, in some specific application scenarios, such as scenarios where the electromagnetic wave transmission in both directions of the reflector needs to exhibit asymmetric properties, the equal reflectivity limits the application fields of plasmonic optical devices.

[0003] In many articles, complex theoretical models such as Rayleigh expansion or time-consuming mathematical methods such as finite-difference time-domain (FDTD) and finite element method (FEM) are used to analyze, design, and optimize plasmonic Bragg reflectors. For example, Li et al. (Li G, Cai L, Xiao F, Pei Y and Xu A 2010 Opt. Express 18 10487) proposed a quantitative calculation method based on a semi-analytical coupled-mode model of plasmonic Bragg reflectors, which model can include different numbers of nanostructures, and using this model can significantly simplify the design and optimization process of the reflector. Recently, asymmetric transmission devices for electromagnetic waves have also been more intensively studied. For example, Fedotov et al. (Fedotov V A, Mladyonov P L, Prosvirnin S L, Rogacheva A V, Chen Y and Zheludev N I 2006 Phys. Rev. Lett. 97 167401) reported a polarization-sensitive transmission effect asymmetric along the wave propagation direction based on a planar chiral structure, Shi et al. (Shi J, Liu X, Yu S, Lv T, Zhu Z, Ma H F and Cui T J 2013 Appl. Phys. Lett. 102 191905) demonstrated the double-band asymmetric transmission of linearly polarized electromagnetic waves in two opposite directions in a bilayer chiral material, and Xu et al. (Xu Y, Gu C, Hou B, Lai Y, Li J and Chen H 2013 Nat. Commun. 4 2561) proposed an optical waveguide for asymmetric light propagation based on gradient-index materials.

[0004] However, the existing asymmetric transmission technologies still fail to achieve a sufficiently high electromagnetic wave asymmetric transmission effect, and the devices formed thereby are relatively single in function, restricting the application of the devices in more scenarios, and the relatively complex device structure also makes the processing cost relatively high. Summary of the Invention

[0005] Aiming at the above existing technical problems, the present application proposes a unidirectional plasmonic Bragg waveguide reflector, by designing a MIM waveguide with longitudinally (i.e., along the electromagnetic wave propagation direction) non-geometrically symmetric periodic nanostructures, so that the reflector has an asymmetric reflection property along the electromagnetic wave propagation direction.

[0006] Specifically, the present application relates to a unidirectional plasmonic Bragg waveguide reflector, comprising a first metal layer, a non-metal layer, and a second metal layer; the non-metal layer includes a core layer, and at least one microstructure formed on the core layer and asymmetric along the electromagnetic wave transmission direction in the core layer and integrally formed with the core layer; the reflector further includes a first port and a second port, the first port and the second port are used to allow the electromagnetic wave to enter the reflector, or to allow the electromagnetic wave to output from the reflector; the first port allows the electromagnetic wave to enter the reflector along the first direction, and the second port allows the electromagnetic wave to enter the reflector along the second direction; when the electromagnetic wave enters the reflector along the first direction, the reflector exhibits a high absorption rate; when the electromagnetic wave enters the reflector along the second direction, the reflector exhibits a high reflectivity.

[0007] Preferably, the first direction and the second direction are two parallel and opposite directions.

[0008] Preferably, when the electromagnetic wave enters the reflector along the first direction, the reflectivity exhibited by the reflector is R + ; when the electromagnetic wave enters the reflector along the second direction, the reflectivity exhibited by the reflector is R - ; let the reflection extinction ratio be 10×lg(R - / R + ), and the reflection extinction ratio of the reflector is greater than 8 dB, preferably greater than 10 dB, and further preferably 11 dB.

[0009] Preferably, there are at least two of the microstructures, and the two microstructures are symmetrically arranged with respect to the core layer; and the two microstructures symmetrically arranged with respect to the core layer together form a microstructure unit, and the reflector includes at least one such microstructure unit.

[0010] Preferably, the microstructure units are arranged at equal intervals along the electromagnetic wave transmission direction and form a periodic structure.

[0011] Preferably, the input and output thicknesses of the first port and the second port of the reflector are equal; the input and output thicknesses ensure that in the waveguide formed by the first metal layer, the non-metal layer, and the second metal layer, the electromagnetic wave only transmits a single fundamental mode.

[0012] Preferably, the cross-section of the microstructure is a triangle, a trapezoid, or a parallelogram.

[0013] Preferably, the cross-section of the micro-structure is a right triangle; one of the right-angled sides of the right triangle coincides with the surface of the core layer, and the other right-angled side is arranged on one side of the direction of electromagnetic wave transmission, extending perpendicularly from the surface of the core layer to the outside of the core layer.

[0014] Preferably, the length of one right-angled side, that is, the width w of the triangle, is in the range of 180 nm - 220 nm, and the other right-angled side, that is, the height h of the triangle, is in the range of 130 nm - 180 nm; more preferably, the width w = 210 nm and the height h = 150 nm.

[0015] Preferably, the wavelength λ of the electromagnetic wave is in the ranges of 765 nm - 820 nm and 505 - 605 nm.

[0016] Preferably, the arrangement period p of the micro-structure units is in the range of 200 nm - 800 nm.

[0017] Preferably, the number N of the micro-structure units satisfies N ≥ 4.

[0018] Preferably, the input / output thickness D 0 = 100 nm, the width w = 210 nm, the height h = 150 nm, the period p = 208 nm, the electromagnetic wave wavelength λ = 800 nm; the number N of the micro-structure units is 4.

[0019] Through the above design, the unidirectional plasmonic Bragg waveguide reflector based on the longitudinal asymmetric micro-structure proposed in this application can achieve unidirectional reflection of electromagnetic waves, that is, when the electromagnetic wave is incident from one side into the waveguide, it shows a high reflection effect, and when it is incident from the other side into the waveguide, it shows a high absorption effect. The reflection extinction ratio generated by the electromagnetic wave incident from both sides of the reflector can reach nearly 11 dB, that is, the reflector can simultaneously realize the functions of a single-direction reflector and a single-direction absorber. Thereby, the flexibility of module control based on this device is greatly improved, and the application range of plasmonic devices is expanded. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Attached Figure 1 : Schematic cross-sectional structure diagram of the unidirectional plasmonic Bragg reflector.

[0021] Attached Figure 2 : Schematic diagram of the left-side incidence of a single nanostructure.

[0022] Attached Figure 3 : Schematic diagram of the right-side incidence of a single nanostructure.

[0023] Attached Figure 4(a): Under the conditions of N = 4, p = 280 nm, and λ = 800 nm, by changing w and h, the formed R + Functional relationship with respect to w and h.

[0024] Appendix Figure 4 (b): Under the conditions of N = 4, p = 280 nm, and λ = 800 nm, by changing w and h, the formed R - Functional relationship with respect to w and h.

[0025] Appendix Figure 4 (c): Under the conditions of N = 4, p = 280 nm, and λ = 800 nm, by changing w and h, the formed |R + -R - | Functional relationship with respect to w and h.

[0026] Appendix Figure 5 : Under the conditions of D 0 = 100 nm, w = 210 nm, h = 150 nm, N = 4, p = 280 nm, the schematic diagram of the change of the reflector with the electromagnetic wave wavelength λ is obtained.

[0027] Appendix Figure 6 : Under the conditions of D 0 = 100 nm, w = 210 nm, h = 150 nm, N = 4, λ = 800 nm, the schematic diagram of the change of the reflector with the microstructure unit period p is obtained.

[0028] Appendix Figure 7 : Under the conditions of D 0 = 100 nm, w = 210 nm, h = 150 nm, p = 208 nm, λ = 800 nm, the schematic diagram of the change of the reflector with the number of microstructure units N is obtained. Detailed implementation manners

[0029] The vocabulary of up, down, left, right, etc. indicating direction features mentioned in this specification is only used to clarify the technical solution with respect to the content in the drawings, and does not have a substantial limiting effect on the direction of the technical solution recorded in this specification. That is, up, down, left, right can be understood as the first side, the second side, the third side, the fourth side, or the first direction, the second direction, the third direction, the fourth direction, or similar explanations. The coordinate system directions mentioned in this specification and the specification drawings, the X-axis direction is the direction parallel to the paper surface and upward, the Z-axis direction is the direction parallel to the paper surface and to the right, and the Y-axis direction is the direction perpendicular to the paper surface and pointing to the reader.

[0030] For example Figure 1As shown, the plasmonic Bragg reflector of this embodiment has a waveguide structure of metal-insulator-metal (MIM), with the upper layer being the first metal layer 1, the middle layer being the non-metal layer 2, and the lower layer being the second metal layer 3. Attached Figure 1 is a schematic cross-sectional view of the X-Z plane of the reflector. The overall structure of the reflector is a flat sheet structure, specifically a structure that extends along the Y direction according to the cross-sectional structure in the attachment Figure 1 . Usually, the dimension of the reflector along the Y direction in the attachment Figure 1 is much larger than the dimensions of the reflector in the other two directions. Therefore, when designing the reflector, there is no need to consider the size of the reflector in the Y direction.

[0031] As Figure 1 shown, the non-metal layer 2 is preferably made of a dielectric material that allows the propagation of electromagnetic waves. The non-metal layer 2 has a core layer 4.

[0032] Electromagnetic waves can be input and output from the end faces of the non-metal layer 2 and can propagate in the non-metal layer 2 along the Z direction. The end faces are specifically the first port 6 on the left side of the reflector, that is, the end face of the non-metal layer 2 on the side of the negative Z-axis of the reflector, and the second port 7 on the right side of the reflector, that is, the end face of the non-metal layer 2 on the side of the positive Z-axis of the reflector. The first port 6 and the second port 7 are used to allow the electromagnetic waves to be input into the non-metal layer 2 or output from the non-metal layer 2. At the first port 6 and the second port 7, the thickness of the non-metal layer 2 is D 0 , that is, the input and output thicknesses of the reflector are both D 0 , and the input and output thickness D 0 is preferably to ensure that only a single fundamental mode is transmitted in the waveguide at a given wavelength.

[0033] The non-metal layer 2 also has microstructures 5 integrally formed on the core layer 4 and protruding in the positive and negative directions of the X axis respectively. The microstructures 5 are preferably asymmetric in cross-sectional shape along the direction of electromagnetic wave propagation, that is, the z direction. The cross-section of the microstructures 5 is an asymmetric triangle, trapezoid, parallelogram, etc. along the z direction.

[0034] Preferably, the cross-sectional shape of the microstructure 5 is a right triangle, where one right-angled side coincides with the surface of the core layer 4, and the other right-angled side is disposed on one side of the second port and extends perpendicularly from the surface of the core layer 4 to the outside of the core layer 4. As shown in the figure, the height of the microstructure 5 in the X direction is h. Further, the microstructure 5 is preferably symmetrically disposed with respect to the core layer 4. Two microstructures 5 that are symmetrically disposed with respect to the core layer 4 form a microstructure unit. Thus, the microstructure unit is a prism structure formed by extending along the Y direction according to its cross-sectional shape. As shown in the attached Figure 1 description, a plurality of microstructure units with exactly the same structure are equally spaced in the Z direction on the core layer 4, thereby forming a periodic structure. The relevant parameters are described as follows: the length of the microstructure unit in the Z direction is w, the repetition period of the microstructure unit in the Z direction is p, the interval between each microstructure unit in the Z direction is (p - w), and the number of microstructure units of the reflector is N.

[0035] When electromagnetic waves are incident on the reflector in the positive Z-axis direction, as Figure 2 shown, if the reflector has only one microstructure unit, the microstructure unit can be regarded as a whole, that is, regarded as a "black box". Electromagnetic waves are incident on the "black box" along the positive Z-axis direction and through the first port 6 of the reflector, and exit from the second port 7 of the reflector. The reflection coefficient formed by the reflector is The transmission coefficient is If the reflector has two microstructure units, then electromagnetic waves are incident on the reflector along the positive Z-axis direction through the first port 6 of the reflector and exit from the second port 7 of the reflector. During the transmission process, after the continuous action of two "black boxes", the reflection coefficient formed by the reflector is The transmission coefficient is And so on, if the reflector has N - 1 microstructure units, then electromagnetic waves are incident on the reflector along the negative Z-axis direction through the first port 6 of the reflector and exit from the second port 7 of the reflector. During the transmission process, after the continuous action of N - 1 "black boxes", the reflection coefficient formed by the reflector is The transmission coefficient is If the reflector has N microstructure units, then electromagnetic waves are incident on the reflector along the positive Z-axis direction through the first port 6 of the reflector and exit from the second port 7 of the reflector. During the transmission process, after the continuous action of N "black boxes", the reflection coefficient formed by the reflector is The transmission coefficient is

[0036] When electromagnetic waves are incident on the reflector in the negative Z-axis direction, as Figure 3As shown, if the reflector has only one such microstructure unit, the microstructure unit can be regarded as a whole, that is, regarded as a "black box". The electromagnetic wave travels along the negative Z-axis, enters the "black box" through the second port 7 of the reflector, and exits from the first port 6 of the reflector. The reflection coefficient formed by the reflector is The transmission coefficient is If the reflector has two such microstructure units, the electromagnetic wave travels along the negative Z-axis, enters through the second port 7 of the reflector, and exits from the first port 6 of the reflector. During the transmission process, it undergoes the continuous action of two "black boxes". The reflection coefficient formed by the reflector is The transmission coefficient is And so on. If the reflector has N - 1 such microstructure units, the electromagnetic wave travels along the negative Z-axis, enters through the second port 7 of the reflector, and exits from the first port 6 of the reflector. During the transmission process, it undergoes the continuous action of N - 1 "black boxes". The reflection coefficient formed by the reflector is The transmission coefficient is If the reflector has N such microstructure units, the electromagnetic wave travels along the negative Z-axis, enters through the second port 7 of the reflector, and exits from the first port 6 of the reflector. During the transmission process, it undergoes the continuous action of N "black boxes". The reflection coefficient formed by the reflector is The transmission coefficient is

[0037] The above main parameters conform to the following recurrence formula:

[0038]

[0039]

[0040]

[0041]

[0042] Among them,

[0043] u = exp[ik 0 n eff (p - w)];

[0044] k 0 = 2π / λ, where λ is the wavelength of the electromagnetic wave;

[0045] n eff is the effective refractive index of the reflector when the reflector is regarded as a whole.

[0046] Therefore, as long as τ is determined by calculating through conventional simulation methods1 , and That is, the properties of the reflector can be determined by simulation.

[0047] It should be noted that according to the principle of reversibility of the optical path, it holds for m = 1, 2, …, N. Therefore, the reflectivity of the plasmonic Bragg reflector can be calculated from the above model and the transmittance T = |τ N | 2 .

[0048] Embodiment

[0049] Select a unidirectional plasmonic Bragg reflector as shown in Figure 1 . The microstructure 5 formed on the non-metal layer 2 inside the reflector is a right triangle, one right side of which coincides with the surface of the core layer 4, and the other right side is arranged on one side of the second port and extends perpendicularly from the surface of the core layer 4 to the outside of the core layer 4.

[0050] In this embodiment, SiO 2 is used as the material for forming the non-metal layer 2, and the input-output thickness is D 0 of 100 nm. That is, the refractive index n sio2 of the non-metal layer 2 is 1.45, and the input-output thickness D 0 is 100 nm.

[0051] When N = 4, a saturated reflectivity difference for incidence from two directions can already be obtained. When the number of the microstructure units N = 4 and the period p = 280 nm are selected, by changing the parameters w and h, the following are obtained Figure 4 as shown in the R + , R - and |R + -R - | as functions of w and h at the electromagnetic wave operating wavelength of λ = 800 nm; where R + is the reflectivity formed when the electromagnetic wave is incident on the reflector from the first port 6 along the positive direction of the Z axis, R - is the reflectivity formed when the electromagnetic wave is incident on the reflector from the second port along the negative direction of the Z axis, and |R + -R - | is the absolute value of the difference between the above two reflectivities R + and R - . From FIGS. Figure 4 (a)-(c), it can be found that R + and R -The maximum reflectivity difference appears at the positions of w = 210 nm and h = 150 nm, and the corresponding maximum reflectivity difference is |R + -R - | = 0.814. That is, by attaching Figure 4 (c) The following can be determined: When the operating wavelength of the electromagnetic wave is λ = 800 nm, SiO 2 is selected as the material of the non-metal layer, and the structural parameters of the reflector are selected as D 0 = 100 nm, w = 210 nm, h = 150 nm, p = 280 nm, the obtained reflectivity difference is |R + -R - | = 0.814. At the same time, there is an attachment Figure 4 It can be seen that within the range of the width w = 180 - 220 nm and the height h = 130 - 180 nm, the reflector shows a very high |R + -R - | value, that is, it shows a high asymmetric transmission property.

[0052] While keeping the structural parameters of the reflector, that is, D 0 = 100 nm, w = 210 nm, h = 150 nm, N = 4, p = 280 nm, by changing the operating wavelength of the electromagnetic wave, the schematic diagram of the change of the reflector with the operating wavelength as shown in the attachment Figure 5 can be obtained. In the figure, the abscissa is the electromagnetic wavelength, and the ordinate is the reflectivity and transmittance in two directions. Let the reflection extinction ratio be 10×lg(R - / R + ). From the attachment Figure 5 it can be seen that at λ = 800 nm, the reflection extinction ratio is as high as 10.97 dB, and within a bandwidth of about more than 50 nm near 800 nm, the reflection extinction ratio can reach 10 dB. And within the ranges of wavelengths of 765 nm - 820 nm and 505 nm - 605 nm, the reflection extinction ratios all reach above 8 dB, forming an obvious asymmetric transmission effect, which can improve the device control sensitivity.

[0053] While keeping the structural parameters of the reflector, that is, D 0 = 100 nm, w = 210 nm, h = 150 nm, N = 4, under the condition of λ = 800 nm, by changing the period of the microstructure unit, the schematic diagram of the change of the reflector with the period of the microstructure unit as shown in the attachment Figure 6 can be obtained. In the figure, the abscissa is the period of the microstructure unit, and the ordinate is the reflectivity and transmittance in two directions.. From the attachment Figure 6It can be seen that there is a periodic variation relationship between the reflectivity and the period of the microstructural unit. When p = 280 nm, p = 500 nm, and p = 720 nm, the reflectivity reaches the maximum value, and as the value of the period p increases, this maximum value decreases accordingly. At the same time, within the range of 200 nm - 800 nm for the period p, the reflection extinction ratio reaches above 10 dB, forming an obvious asymmetric transmission effect, which can improve the device control sensitivity.

[0054] While keeping the structural parameters of the reflector unchanged, that is, D 0 = 100 nm, w = 210 nm, h = 150 nm, p = 208 nm, and λ = 800 nm, by changing the number N of microstructural units, the schematic diagram of the change of the reflector with the number of microstructural units as shown in the appendix can be obtained. In the figure, the abscissa is the period of the microstructural unit, and the ordinate is the reflectivity and transmittance in two directions... From the appendix Figure 7 it can be seen that after the number of the microstructural units exceeds 4, R Figure 7 has reached the saturation value. Therefore, the reflection extinction ratio also increases rapidly with the number of microstructural units and reaches saturation after N = 4. That is to say, choosing N ≥ 4 can achieve a large enough reflection extinction ratio to form an obvious asymmetric transmission effect, which can improve the device control sensitivity. - From the transmittance value of the ordinate in the appendix, it can be seen that the value of the transmittance is very small. And the obvious reflection extinction ratio caused by the reflector indicates that for the plasmonic Bragg waveguide reflector involved in the present invention, when the electromagnetic wave is incident from the right port, most of the energy will be reflected back; while when the electromagnetic wave is incident from the left port, most of the energy will be absorbed.

[0055] In summary, the present application relates to a unidirectional plasmonic Bragg waveguide reflector with a longitudinally asymmetric structure. When the electromagnetic wave is incident from the left port and the right port, there is a very large difference in reflection and absorption. This asymmetric reflection property along the direction of electromagnetic wave propagation is mainly achieved by designing a MIM waveguide with a longitudinally (i.e., the direction of electromagnetic wave transmission) non-geometrically symmetric structure composed of periodic nanostructures. Thus, this unidirectional plasmonic Bragg waveguide reflector based on a longitudinally asymmetric microstructure can achieve unidirectional reflection of electromagnetic waves, that is, when the electromagnetic wave is incident from one side into the waveguide, a high reflection effect appears, and when it is incident from the other side into the waveguide, a high absorption effect appears. Therefore, it can make the plasmonic device have more abundant control methods and improve the flexibility of device design and use. Figures 5 - 7

[0056]

[0057] The above description is only to illustrate some embodiments of the present invention by way of diagrams. Since it is easy for those of ordinary skill in the same technical field to make several modifications and alterations on this basis, this specification is not intended to limit the present invention to the specific structures and applicable scopes shown and described. Therefore, all corresponding modifications and equivalents that may be utilized belong to the scope of the patent applied for by the present invention.

Claims

1. A unidirectional plasmonic Bragg waveguide reflector, comprising a first metal layer, a non-metal layer, and a second metal layer; Characterized in that, The non-metal layer includes a core layer, and at least one microstructure formed on the core layer and asymmetric along the direction of electromagnetic wave transmission in the core layer and integrally formed with the core layer; The reflector further includes a first port and a second port, and the first port and the second port are used to allow the electromagnetic wave to enter the reflector, or to allow the electromagnetic wave to output from the reflector; the first port allows the electromagnetic wave to enter the reflector along a first direction, and the second port allows the electromagnetic wave to enter the reflector along a second direction; When the electromagnetic wave is incident from the first port along the first direction of the reflector, the reflector exhibits a high absorption rate; When the electromagnetic wave is incident from the second port along the second direction of the reflector, the reflector exhibits a high reflectivity; The cross-section of the microstructure is a triangle, a trapezoid or a parallelogram; There are at least two of the microstructures, and the two microstructures are symmetrically arranged with respect to the core layer; and the two microstructures symmetrically arranged with respect to the core layer together form a microstructure unit, and the reflector includes at least one such microstructure unit.

2. The reflector according to claim 1, Characterized in that, The first direction and the second direction are two parallel and opposite directions.

3. The reflector according to claim 1, Characterized in that, When the electromagnetic wave is incident along the first direction of the reflector, the reflectivity exhibited by the reflector is R + When the electromagnetic wave is incident along the second direction of the reflector, the reflectivity of the reflector is R - ; Assume the reflection extinction ratio is 10×lg(R - / R + ), the reflection extinction ratio of the reflector is greater than 8dB.

4. The reflector according to claim 1, Characterized in that, The microstructure units are arranged at equal intervals along the direction of electromagnetic wave transmission and form a periodic structure.

5. The reflector according to any one of claims 1-3, Characterized in that, The input and output thicknesses of the first port and the second port of the reflector are equal; the input and output thicknesses ensure that in the waveguide formed by the first metal layer, the non-metal layer and the second metal layer, the electromagnetic wave only transmits a single fundamental mode.

6. The reflector according to claim 5, Characterized in that, The cross-section of the microstructure is a right triangle; one of the right sides of the right triangle coincides with the surface of the core layer, and the other right side is arranged on the side of the second port and extends perpendicularly from the surface of the core layer to the outside of the core layer.

7. The reflector according to claim 6, Characterized in that, The length of one of the right sides, that is, the width w of the triangle, is in the range of 180nm - 220nm, and the other right side, that is, the height h of the triangle, is in the range of 130nm - 180nm.

8. The reflector according to claim 7, Characterized in that, The width w = 210nm, and the height h = 150nm.

9. The reflector according to any one of claims 1-3, Characterized in that, The wavelength λ of the electromagnetic wave is in the ranges of 765nm - 820nm and 505 - 605nm.

10. The reflector according to claim 7 or 8, Characterized in that, The arrangement period p of the microstructure units is in the range of 200nm - 800nm.

11. The reflector according to claim 4 or 6, characterized in that, the arrangement period p of the microstructure units is in the range of 200 nm to 800 nm.

12. The reflector according to claim 1, characterized in that, the number N of the microstructure units is N≥4.

13. The reflector according to claim 10, characterized in that, The input / output thickness D 0 = 100 nm, the width w = 210 nm, the height h = 150 nm, the period p = 208 nm, the electromagnetic wave wavelength λ = 800 nm; the number of microstructural units N = 4.

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