Terahertz wave circular dichroism and linear dichroism switchable controller

Abstract

The invention discloses a terahertz wave circular dichroism and linear dichroism switchable controller. The terahertz wave circular dichroism and linear dichroism switchable controller structurally comprises a dielectric layer embedded into a U-shaped silicon rod, a dielectric layer embedded into a metal opening square ring, a dielectric layer and a substrate layer, strong circular dichroism (CD) is generated due to interaction between the top layer composite structure and the dielectric layer, and the conductivity of the light-sensitive silicon pump light can be changed by changing the light-sensitive silicon pump light, so that a circular dichroism and linear dichroism switching function is realized. The structure is simple, dual-polarization-state dichroism can be achieved, and the dual-polarization-state dichroism laser can be used in the fields of polarization detection, near-field imaging and the like and has very wide application prospects.

Description

Technical Field

[0001] The present invention relates to the field of terahertz wave controllers, and in particular to a terahertz wave circular dichroism and linear dichroism switchable controller. Background Art

[0002] Terahertz waves (0.1-10 THz) are located in the transition region between electronics and photonics, and between microwaves and infrared in the electromagnetic spectrum. Their unique spectral position enables terahertz waves to have microwave penetration and optical imaging capabilities. At the same time, they also exhibit many electromagnetic properties that microwave and infrared bands do not have, such as broadband, coherence, transient and low photon energy. The structure of an object itself cannot be translated or rotated to coincide with its mirror image to form chirality. The structures of many substances in nature have chirality, such as proteins, amino acids, DNA, etc. Therefore, chirality is very important to life, and thus detecting the chirality of substances has become a hot topic for many scientific researchers. Chiral materials have different absorption in right circular polarization and left circular polarization. This phenomenon is called circular dichroism (CD). CD can be defined as the different absorption / reflection of chiral media for different circularly polarized waves, and the difference is circular dichroism. Linear dichroism can be defined as the difference in absorption / reflection of different linearly polarized waves. Circular dichroism and linear dichroism can be used to detect the chirality of a substance or structure. The optical chiral response (circular dichroism and linear dichroism) brought by the chiral structure has important application prospects in the fields of polarization imaging, biomedical detection, optical communication, circular dichroism spectroscopy, etc.

[0003] Since the chiral signals of biological molecules in nature are relatively weak and difficult to detect, by studying artificial chiral metasurfaces and constructing different chiral metasurfaces, the chiral signal testing of biomolecules can be easily realized. It is an inevitable trend to design simple and adjustable chiral metasurface devices. At the same time, it is necessary to comprehensively consider multiple factors such as materials, processes, efficiency and functions. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problem that the prior art cannot realize circular dichroism and linear dichroism at the same time, overcome the shortcomings of complex structure, practical production difficulties and high cost, and provide a terahertz wave circular dichroism and linear dichroism switchable controller.

[0005] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0006] A terahertz wave circular dichroism and linear dichroism switchable controller, which consists of a composite structure composed of four layers with the same square outer contour, which are, from top to bottom, a first BCB dielectric layer, a second BCB dielectric layer, a third BCB dielectric layer and a silicon substrate; a U-shaped silicon rod made of photosensitive silicon is embedded in the first BCB dielectric layer, and the U-shaped silicon rod consists of a first rectangular silicon rod and two second rectangular silicon rods arranged on the long sides of both ends of the first rectangular silicon rod, and the first rectangular silicon rod is arranged along the diagonal of the first BCB dielectric layer; a metal open square ring is embedded in the second BCB dielectric layer, and the metal open square ring has two openings symmetrically opened on two opposite sides; the material of the silicon substrate is photosensitive silicon.

[0007] Preferably, the composite structure is arranged periodically on a plane, with a period of 25 μm to 35 μm in the x-direction and a period of 25 μm to 35 μm in the y-direction.

[0008] Preferably, the thickness of the first BCB dielectric layer and the U-shaped silicon rod are both 0.1μm to 1.0μm; in the U-shaped silicon rod, the length of the first rectangular silicon rod is 15μm to 25μm, the width is 1μm to 3μm, and the length of the second rectangular silicon rod is 1μm to 2μm, the width is 1μm to 2μm.

[0009] Furthermore, the dielectric constant of the U-shaped silicon rod is 11.9.

[0010] Preferably, the thickness of the second BCB dielectric layer and the metal open square ring are both 0.1 μm to 1.0 μm, wherein the length of the metal open square ring is 15 μm to 25 μm, the width is 1 μm to 5 μm, and the opening length on a single side is 1 μm to 5 μm.

[0011] Furthermore, the metal open square ring is made of gold, and its electrical conductivity is 4.561×10 7 S / m.

[0012] Preferably, the thickness of the third BCB dielectric layer is 5 μm to 15 μm.

[0013] Preferably, the dielectric constants of the BCB dielectric materials in the first BCB dielectric layer, the second BCB dielectric layer and the third BCB dielectric layer are all 2.67.

[0014] Preferably, the silicon substrate has a thickness of 0.5 μm to 1.5 μm.

[0015] Preferably, the controller controls the photosensitive silicon in the device to be in a metallic state by pumping light, thereby realizing circular dichroism and linear dichroism in different frequency bands; and realizes dynamic tuning of the circular dichroism and linear dichroism amplitudes by changing the conductivity of the photosensitive silicon.

[0016] The terahertz wave circular dichroism and linear dichroism switchable controller designed by the present invention generates strong circular dichroism (CD) due to the interaction between the top composite structure and the dielectric layer, and can change its conductivity by changing the photosensitive silicon pump light, so that the device can simultaneously realize the two functions of circular dichroism and linear dichroism in different frequency bands, and there is no crosstalk between the two functions. The present invention can realize dual-polarization state dichroism, and has the advantages of easy large-scale integration, simple structure, small size, low cost, easy production, etc. It can be used in the fields of polarization detection and near-field imaging, and has a very broad application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of the three-dimensional structure of a terahertz wave circular dichroism and linear dichroism switchable controller;

[0018] Figure 2 is a top view schematic diagram of a dielectric layer embedded with a U-shaped silicon rod;

[0019] Figure 3 is a top view schematic diagram of a dielectric layer embedded with a metal open square ring;

[0020] Figure 4 is the conductivity of photosensitive silicon σ Si =5×10 5 S / m, the reflection coefficient curve of the designed structure under circular polarization wave incidence;

[0021] Figure 5 is the conductivity of photosensitive silicon σ Si =5×10 5 S / m, the reflectivity and circular dichroism curves of the designed structure under circularly polarized wave incidence;

[0022] Figure 6 is the conductivity of photosensitive silicon σ Si =5×10 5 S / m, the circular dichroism spectrum of the designed structure when the incident angle of circularly polarized wave increases from -60° to 60°;

[0023] Figure 7 is the conductivity of photosensitive silicon σ Si =5×10 5 S / m, the circular dichroism spectrum of the designed structure when the polarization angle of circularly polarized wave increases from 0° to 90°;

[0024] Figure 8 The conductivity of photosensitive silicon increases from 1S / m to 5×10 5 S / m, the change of circular dichroism peak.

[0025] Fig. 9 is the conductivity of photosensitive silicon σ Si =5×105 S / m, the reflection coefficient curve of the designed structure under the incidence of linearly polarized wave;

[0026] Fig.10 is the conductivity of photosensitive silicon σ Si =5×10 5 S / m, the absorptivity and linear dichroism curves of the designed structure under linear polarized wave incidence;

[0027] Fig.11 is the conductivity of photosensitive silicon σ Si =2×10 5 S / m, the linear dichroism spectrum of the designed structure when the incident angle of the linear polarization wave increases from -0° to 50°;

[0028] Fig.12 The conductivity of photosensitive silicon increases from 1S / m to 5×10 5 S / m, the change of linear dichroism peak. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation mode of the present invention is described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0030] In a preferred embodiment of the present invention, a terahertz wave circular dichroism and linear dichroism switchable controller is provided. Figure 1 As shown in FIG. 1 , it is composed of four layers with the same square outer contour to form a composite structure, which are the first BCB dielectric layer 1, the second BCB dielectric layer 2, the third BCB dielectric layer 3 and the silicon substrate 4 from top to bottom. The outer contours of the four layers are the same, so the plane contour of the entire device is also a square. The main bodies of the first BCB dielectric layer 1, the second BCB dielectric layer 2 and the third BCB dielectric layer 3 are all made of BCB material (Benzocyclobutene). A U-shaped silicon rod made of photosensitive silicon is embedded in the first BCB dielectric layer 1, as shown in FIG. Figure 2 As shown, the U-shaped silicon rod is composed of a first rectangular silicon rod and two second rectangular silicon rods. The two second rectangular silicon rods are arranged at both ends of the first rectangular silicon rod and are both located on one side of a long side of the rectangle. The whole is equivalent to a rectangular ring with one long side missing. And the first rectangular silicon rod is arranged along the diagonal line of the first BCB dielectric layer 1. A metal open square ring is embedded in the second BCB dielectric layer 2, as shown in FIG. Figure 3As shown, the metal open square ring has two openings symmetrically formed on two opposite sides. The material of the silicon substrate 4 is photosensitive silicon.

[0031] The composite structure is arranged periodically on the plane, with a period P in the x direction. x 25μm~35μm, y direction period P y 25μm~35μm, that is to say, the plane outline of the device composed of a single composite structure and the outer outline of the four-layer body are both P x ×P y .

[0032] The specific materials and parameters of the terahertz wave circular dichroism and linear dichroism switchable controller are as follows:

[0033] The thickness of the first BCB dielectric layer 1 and the U-shaped silicon rod are both 0.1μm to 1.0μm; in the U-shaped silicon rod, the length of the first rectangular silicon rod is 15μm to 25μm, the width is 1μm to 3μm, the length of the second rectangular silicon rod is 1μm to 2μm, and the width is 1μm to 2μm (here, the length direction of the second rectangular silicon rod is defined to be parallel to the length direction of the first rectangular silicon rod, and the width direction of the second rectangular silicon rod is perpendicular to the length direction of the first rectangular silicon rod). The dielectric constant of the U-shaped silicon rod is 11.9. The thickness of the second BCB dielectric layer 2 and the metal open square ring are both 0.1μm to 1.0μm, the length of the metal open square ring is 15μm to 25μm, the width is 1μm to 5μm, and the length of the opening on a single side is 1μm to 5μm. The material of the metal open square ring is gold, and the conductivity is 4.561×10 7 The thickness of the third BCB dielectric layer 3 is 5 μm to 15 μm. The dielectric constants of the BCB dielectric materials in the first BCB dielectric layer 1, the second BCB dielectric layer 2 and the third BCB dielectric layer 3 are all 2.67. The thickness of the silicon substrate 4 is 0.5 μm to 1.5 μm.

[0034] The controller controls the photosensitive silicon in the device to be in a metallic state by pumping light, thereby realizing both circular dichroism and linear dichroism in different frequency bands; and by changing the conductivity of the photosensitive silicon, dynamic tuning of the circular dichroism and linear dichroism amplitudes can be achieved.

[0035] The above-mentioned terahertz wave circular dichroism and linear dichroism switchable controller is applied to a specific example below to demonstrate its technical effect.

[0036] Example

[0037] In this embodiment, the shapes of the components of the terahertz wave circular dichroism and linear dichroism switchable controller are as described above. Figure 1 to Figure 3 , I will not go into details here. However, the specific parameters of each component are as follows:

[0038] The composite structure is arranged periodically on the plane, with a period P in the x direction. x 28μm, y direction period P y The thickness of the first BCB dielectric layer 1 and the U-shaped silicon rod is 0.2 μm. In the U-shaped silicon rod, the length of the first rectangular silicon rod is 17 μm and the width is 2 μm, and the length of the second rectangular silicon rod is 2 μm and the width is 1 μm. The dielectric constant of the U-shaped silicon rod is 11.9. The thickness of the second BCB dielectric layer 2 and the metal open square ring is 0.3 μm. The length of the metal open square ring is 17 μm and the width is 1 μm. The length of the opening on a single side is 4 μm. The material of the metal open square ring is gold, and the conductivity is 4.561×10 7 S / m. The thickness of the third BCB dielectric layer 3 is 9 μm. The dielectric constants of the BCB dielectric materials in the first BCB dielectric layer 1, the second BCB dielectric layer 2 and the third BCB dielectric layer 3 are all 2.67. The thickness of the silicon substrate 4 is 0.6 μm.

[0039] In this device, the conductivity of the photosensitive silicon can be adjusted by inputting pump light from the upper surface of the first BCB dielectric layer 1, thereby achieving functional control of the device. Si =5×10 5 S / m), the device can realize circular dichroism and linear dichroism functions. When circularly polarized waves are incident, a circular dichroism effect with a bandwidth of about 0.74THz can be achieved in the frequency band of 3.66~4.40THz; when linearly polarized waves are incident, the linear dichroism values ​​of the device at frequencies of 6.76THz, 7.45THz and 8.39THz are 0.71, -0.57 and 0.33 respectively. Dynamic tuning of the amplitudes of circular dichroism and linear dichroism can be achieved by changing the conductivity of photosensitive silicon, and the amplitude modulation depths reach 98% and 96.1% respectively. Figure 4 As shown in the figure, the co-polarization reflection curve of the left circularly polarized wave (r -- ) and the co-polarization reflection curve of right-hand circularly polarized wave (r ++ ) is consistent with the cross-polarization reflection curve of the right-hand circularly polarized wave (r -+ ) and the cross-polarization reflection curve of left-hand circularly polarized wave (r +- ) has a large difference. When the frequency is 4.03THz, r -+ Greater than 0.9, r +- is close to 0, indicating that at this frequency, the designed structure reflects most of the right-hand circularly polarized waves, but does not reflect the left-hand circularly polarized waves. Figure 5As shown in the figure, at a frequency of 4.03THz, the reflectivity of the designed structure to the left-hand circularly polarized wave is 0, and the reflectivity to the incident right-hand circularly polarized wave reaches 86.7%. At this time, the circular dichroism value is close to 1, and in the frequency band of 3.66~4.40THz, the circular dichroism is greater than 0.9, and the bandwidth is about 0.74THz. Figure 6 As shown in the figure, when the incident angle of the circularly polarized wave is less than 50°, the circular dichroism of the designed structure is greater than 0.85 in the range of 3.84 to 4.33 THz, and the bandwidth is 0.49 THz, indicating that the structure has good wide incident angle characteristics. Figure 7 As shown in Figure 2, in the frequency range of 3.61 to 4.55 THz, increasing the polarization angle of the incident terahertz wave from 0° to 90° has no effect on the circular dichroism value, and the amplitude is always greater than 0.85. Figure 8 As shown, when the conductivity of photosensitive silicon increases from 5×10 5 When S / m drops to 1S / m, the circular dichroism value of the designed structure drops from 0.98 to 0 at a frequency of 4.03THz, and the amplitude modulation depth is 98%. Fig. 9 As shown in the figure, in the frequency band of 4.50 to 9.00 THz, the cross reflection curve r corresponding to the linear polarization wave yx =r xy , and the co-polarization reflection curve r xx and r yy There are obvious differences. Fig.10 As shown in the figure, at a frequency of 6.76THz, the absorption rates of x-polarization and y-polarization are significantly different. The absorption rate is 0.87 for x-polarization wave incident and 0.16 for y-polarization wave incident. At this time, the linear dichroism amplitude is 0.71, indicating that the structure strongly absorbs x-polarization waves and reflects y-polarization waves. At 7.45THz and 8.39THz, the corresponding linear dichroisms are -0.57 and 0.33, respectively. Fig.11 As shown, when the conductivity of photosensitive silicon σ Si =2×10 5 When the incident angle changes from 0° to 50°, the linear dichroism amplitude gradually decreases and produces a slight blue shift. Fig.12 As shown, the conductivity of photosensitive silicon increases from 2×10 5 When S / m drops to 1S / m, the linear dichroism value of the structure drops from 0.77 to 0.03, and the amplitude modulation depth is 96.1%.

[0040] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A terahertz wave circular dichroism and linear dichroism switchable controller, characterized in that: The invention relates to a composite structure composed of four layers with the same square outer contour, which are, from top to bottom, a first BCB dielectric layer (1), a second BCB dielectric layer (2), a third BCB dielectric layer (3) and a silicon substrate (4); the first BCB dielectric layer (1) is embedded with a U-shaped silicon rod made of photosensitive silicon, the U-shaped silicon rod is composed of a first rectangular silicon rod and two second rectangular silicon rods arranged on the long sides of the two ends of the first rectangular silicon rod, and the first rectangular silicon rod is arranged along the diagonal of the first BCB dielectric layer (1); the second BCB dielectric layer (2) is embedded with a metal open square ring, and the metal open square ring has two openings symmetrically opened on two opposite sides; the material of the silicon substrate (4) is photosensitive silicon.

2. The terahertz wave circular dichroism and linear dichroism switchable controller according to claim 1, characterized in that: The composite structure is arranged periodically on a plane, with a period of 25 μm to 35 μm in the x-direction and a period of 25 μm to 35 μm in the y-direction.

3. The terahertz wave circular dichroism and linear dichroism switchable controller according to claim 1, characterized in that: The thickness of the first BCB dielectric layer (1) and the U-shaped silicon rod are both 0.1 μm to 1.0 μm; in the U-shaped silicon rod, the length of the first rectangular silicon rod is 15 μm to 25 μm, and the width is 1 μm to 3 μm, and the length of the second rectangular silicon rod is 1 μm to 2 μm, and the width is 1 μm to 2 μm.

4. The terahertz wave circular dichroism and linear dichroism switchable controller according to claim 3, characterized in that: The dielectric constant of the U-shaped silicon rod is 11.

9.

5. The terahertz wave circular dichroism and linear dichroism switchable controller according to claim 1, characterized in that: The thickness of the second BCB dielectric layer (2) and the metal open square ring are both 0.1 μm to 1.0 μm, wherein the length of the metal open square ring is 15 μm to 25 μm, the width is 1 μm to 5 μm, and the length of the opening on a single side is 1 μm to 5 μm.

6. The terahertz wave circular dichroism and linear dichroism switchable controller according to claim 5, characterized in that: The metal open square ring is made of gold, and its conductivity is 4.561×10 7 S / m.

7. The terahertz wave circular dichroism and linear dichroism switchable controller according to claim 1, characterized in that: The thickness of the third BCB dielectric layer (3) is 5 μm to 15 μm.

8. The terahertz wave circular dichroism and linear dichroism switchable controller according to claim 1, characterized in that: The dielectric constants of the BCB dielectric materials in the first BCB dielectric layer (1), the second BCB dielectric layer (2) and the third BCB dielectric layer (3) are all 2.

67.

9. The terahertz wave circular dichroism and linear dichroism switchable controller according to claim 1, characterized in that: The silicon substrate (4) has a thickness of 0.5 μm to 1.5 μm.

10. The terahertz wave circular dichroism and linear dichroism switchable controller according to claim 1, characterized in that: The controller controls the photosensitive silicon in the device to be in a metallic state by pumping light, thereby realizing circular dichroism and linear dichroism in different frequency bands; and realizes dynamic tuning of the circular dichroism and linear dichroism amplitudes by changing the conductivity of the photosensitive silicon.

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