A design method for dual-band spin-selective transmission metasurface device

Abstract

The present invention discloses a method for designing a dual-band spin-selective transmission metasurface device, comprising S1, designing a basic structure based on high-resistance silicon, wherein the basic structure is an H-type dielectric column; S2, the basic structure in step S1 is arranged periodically, and the metasurface composed of the periodic arrangement of the structure realizes dual-band spin-selective transmission. The present invention discloses a terahertz metasurface device that realizes dual-band spin-selective transmission. The metasurface proposed by the present invention is composed of a single-layer all-silicon material, which significantly reduces the processing difficulty and saves the production cost. The present invention can realize spin-selective transmission in two frequency bands and realize two opposite chiral effects in the two frequency bands, which provides a new idea for the design of terahertz spin-selective transmission devices.

Description

Technical Field

[0001] The invention belongs to the technical field of novel artificial electromagnetic materials and terahertz science and technology, and specifically relates to a design method for a dual-band spin-selective transmission metasurface device. Background Art

[0002] Chirality is a special property indicating that there is no mirror symmetry in an object, just like the left and right hands of humans, which cannot be superimposed no matter how we move or rotate them. These chiral structures are widely present in nature, such as amino acids, sugars, and crystals. The optical response of chiral media to circularly polarized (CP) light can be described as optical activity and circular dichroism (CD), and is widely used in medical diagnosis, communication and other fields. However, due to the matching of the size scale of chiral materials and the wavelength of incident light, the chiral optical response of these materials is weak.

[0003] In order to effectively enhance the chiral optical response in natural media, periodically arranged artificial metamaterials have been proposed to improve the chiral optical properties by several orders of magnitude. However, the complexity and high cost of three-dimensional manufacturing have hindered the development of spin-selective transmission metamaterials. In recent years, planar chiral metamaterials, known as chiral metasurfaces, have overcome the above challenges well, which have attracted great attention in theoretical research and practical applications due to their different transmission or reflection responses to two orthogonal circular polarizations. Based on the above characteristics, many polarization devices have been proposed for use in CD spectroscopy, optical sensing and other fields. Most chiral metasurfaces have been proposed to enhance single-band CD or realize dynamic manipulation of single-band chiral optical responses, but multi-band chiral optical responses have not yet been achieved.

[0004] To this end, the present invention designs a single-layer all-silicon terahertz meta-atom, and the metasurface composed of the meta-atom has a dual-band chiral response characteristic. Moreover, the metasurface has opposite spin selective transmission at two frequency bands. Summary of the invention

[0005] The purpose of the present invention is to provide a dual-band spin-selective transmission metasurface device design method to solve or improve the above-mentioned problems in the prior art.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A dual-band spin-selective transmission metasurface device design method specifically comprises the following steps:

[0008] S1. Based on high-resistance silicon, the basic structure is designed, and the basic structure is an H-type dielectric column;

[0009] S2. The basic structure in step S1 is arranged periodically, and the metasurface composed of the periodic arrangement of the structure realizes dual-band spin-selective transmission.

[0010] Furthermore, the basic structure in step S1 is an H-type dielectric column, and its specific parameters depend on the specific operating frequency.

[0011] Furthermore, in step S2, the metasurface operates in a frequency band near 1.2 and 1.6 THz, the total thickness of silicon is 500 μm, the etching height of the dielectric column is 200 μm, the length of the rectangular strips on both sides of the dielectric column is 50-80 μm, the width is 15-30 μm, and the angle with the x-axis is 45°; the center spacing of the rectangular strips on both sides of the dielectric column is 70-100 μm, and the width of the column connecting the rectangular strips on both sides is 10-25 μm. The period of the entire unit is 140-180 μm.

[0012] The dual-band spin-selective transmission metasurface device design method provided by the present invention has the following beneficial effects:

[0013] The present invention discloses a terahertz metasurface device that realizes dual-band spin-selective transmission. The metasurface proposed in the present invention is composed of a single-layer all-silicon material, which significantly reduces the processing difficulty and saves the production cost. The present invention can realize spin-selective transmission in two frequency bands and realize two opposite chiral effects in the two frequency bands, which provides a new idea for the design of terahertz spin-selective transmission devices.

[0014] The present invention can realize dual-band spin-selective transmission in the terahertz band, which provides a new solution for chiral multi-band and broadband chiral metasurfaces.

[0015] At the same time, the dual-band spin-selective transmission metasurface designed by the present invention has opposite chiral responses in each frequency band, which provides a new direction for future applications in the fields of sensing and medicine. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 (a) is a three-dimensional image of a single meta-atom, and (b) is a top view of a single meta-atom.

[0017] Figure 2 (a) is the transmission coefficient of a single meta-atom under different circularly polarized incident light, and (b) is the CD of a single meta-atom under different incident wavelengths.

[0018] Figure 3 (a) is the response of the metasurface to 1.2THz incident circular polarization, and (b) is the response of the metasurface to 1.6THz incident circular polarization. DETAILED DESCRIPTION

[0019] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0020] Example 1, reference Figure 1 The dual-band spin-selective transmission metasurface device design method of this scheme specifically includes the following steps:

[0021] S1. Design the basic structure so that it can achieve dual-band spin-selective transmission.

[0022] S2. Arrange the basic structure designed in step 1 in a periodic manner.

[0023] The above designs are all based on high-resistance silicon, and the thickness of high-resistance silicon is 500μm. The basic structure described in step one is an H-type dielectric column. In the present invention, the super surface works in the frequency band near 1.2 and 1.6THz. The total thickness of silicon is t1+t2=500μm, the etching height of the dielectric column is t2=200μm, and the length of the rectangular strips on both sides of the dielectric column is l1=70μm, the width is w1=22μm, and it presents an angle of 45° with the x-axis. The center spacing of the rectangular strips on both sides of the dielectric column is l2=90μm, and the width of the column connecting the rectangular strips on both sides is w2=16μm. The period of the entire unit is P=150μm.

[0024] Embodiment 2 specifically includes:

[0025] S1. Design the basic structure so that it can achieve dual-band spin-selective transmission. Figure 1 As shown, the basic structure is an H-type dielectric column. The metasurface in the present invention operates in the frequency band around 1.2 and 1.6 THz. Figure 1 (a) It can be seen that the total thickness of silicon is t1+t2=500μm, and the etching height of the dielectric pillar is t2=200μm. Figure 1 (b) is a top view of the unit. The length of the rectangular strips on both sides of the dielectric column is l1 = 70μm, the width is w1 = 22μm, and it forms a 45° angle with the x-axis. The center spacing of the rectangular strips on both sides of the dielectric column is l2 = 90μm, and the width of the column connecting the rectangular strips on both sides is w2 = 16μm. The period of the entire unit is P = 150μm. Figure 2 (a), the “+” and “-” in the subscripts represent right-handed circular polarization and left-handed circular polarization, respectively. -+ "For example, it represents the transmission coefficient of right-handed circular polarization incident and left-handed circular polarization outgoing. When the incident terahertz wave is around 1.2THz, t-+ is much larger than the other three results; when the incident terahertz wave is around 1.6THz, t +- is much greater than the other three results. Figure 2 (b) with Figure 1 The results in (a) are consistent. When the incident terahertz wave is around 1.2THz, the incident left-handed circularly polarized wave is polarized and converted into a right-handed circularly polarized wave by the unit, while the incident right-handed circularly polarized wave cannot pass through the unit. When the incident terahertz wave is around 1.6THz, the chiral response presented by the unit is opposite to the frequency band around 1.2THz.

[0026] S2, such as Figure 3 The basic structure of the design is arranged periodically with a period of P = 150 μm, and the size of the metasurface is 1.2 × 1.2 cm 2 .like Figure 3 (a) When a 1.2THz right-handed circularly polarized wave is incident on the metasurface, the right-handed circular polarization will be reflected, while when a left-handed circularly polarized wave is incident on the metasurface, the outgoing wave contains almost only the right-handed circularly polarized component. Figure 3 (b) When the incident frequency is 1.6 THz, the chiral response produced by the metasurface is opposite to that when the incident frequency is 1.2 THz.

[0027] In summary, the metasurface proposed by the present invention is composed of a single layer of all-silicon material, which significantly reduces the difficulty of processing and saves the production cost. The present invention can achieve spin-selective transmission in two frequency bands. The present invention can achieve two opposite chiral effects in two frequency bands, which provides a new platform for the application of terahertz metasurfaces in the fields of medicine and communication.

[0028] Although the specific implementation of the invention is described in detail in conjunction with the drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A dual-band spin-selective transmission metasurface device design method, characterized in that: The specific steps include: S1. Based on high-resistance silicon, the basic structure is designed, and the basic structure is an H-type dielectric column; S2, the basic structure in step S1 is arranged periodically, and the metasurface composed of the periodic arrangement of the structure realizes dual-band spin selective transmission; The basic structure in step S1 is an H-type dielectric column, and its specific parameters depend on the specific operating frequency; The step S2 metasurface operates in a frequency band near 1.2 and 1.6 THz, the total thickness of silicon is 500 μm, the etching height of the dielectric column is 200 μm, the length of the rectangular strips on both sides of the dielectric column is 50-80 μm, the width is 15-30 μm, and it forms an angle of 45° with the x-axis; the center spacing of the rectangular strips on both sides of the dielectric column is 70-100 μm, the width of the column connecting the rectangular strips on both sides is 10-25 μm, and the period of the entire unit is 140-180 μm.

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