CN110146946A - A terahertz integrated device with an asymmetric curved structure - Google Patents

Abstract

The invention discloses a terahertz integrated device with an asymmetric curved structure, which includes a substrate and a metal thin film horizontally arranged on the substrate. , and the side metal films arranged on both sides of the central metal film. The included angle between the line and the central metal film is less than 90 degrees, and regularly arranged sawtooth structures are arranged on both side walls of the central metal film and the side metal films. The device of the present invention has strong versatility, can still produce preset effects in different wave bands, and does not need to change the designed geometric structure, and the applicable range of the device can be expanded, and research in most terahertz wave bands can be carried out.

Description

A terahertz integrated device with an asymmetric curved structure

technical field

The invention relates to the technical field of terahertz devices, in particular to a terahertz integrated device with an asymmetric curved structure.

Background technique

Terahertz waves are generally defined as electromagnetic waves with frequencies in the range of 0.1 to 10 THz. The English of terahertz is Terahertz (THz), 1THz=10 ¹² Hz, and the wavelength is 30-3000 μm.

For the design of surface plasmon polaritons (SPPs) device structure, Xiaoyong Liu, a related research group at home and abroad, has conducted research in this area as follows: The team of the Department of Electronic Engineering, School of Electronic Science and Engineering, Nanjing University designed a symmetrical corrugated thin film based on Structured planar plasmonic waveguide device, based on conformal surface plasmon (CSP), a symmetrical zigzag curved metal structure was proposed, and the influence of its depth characteristics on the propagation distance was studied. At the same time The experimental study of the surface plasmon waveguide structure was carried out in the microwave frequency band. The research results show that reducing the height of the trench array can increase the propagation distance of surface plasmons, so the structure can be optimized to compensate for part of the metal loss.

The schematic diagram of the surface plasmon polaritons waveguide is shown in Figure 1. From Figure 2, we can see that this structure can only achieve an output of more than 90% at a specific frequency, but cannot achieve output in a certain frequency band.

Another similar scheme is a three-layer three-dimensional structure proposed by Huang Wei et al. of Guilin University of Electronic Science and Technology. As shown in the schematic diagram 3, the upper layer structure is the waveguide input layer, and the generated SPPs are coupled to the middle layer, and finally output at the bottom layer. , compared with planar structures, the production of multi-layer structures is relatively more cumbersome.

Looking back at the previous research, it is not difficult to find that many researchers regard the independence of device design, the applicable wavelength band of the device is very short, and the versatility is very poor. The devices designed by many researchers can only produce effects at a specific excitation frequency, and it is difficult to achieve preset effects in other bands after changing the parameters. For the design of the SPPs device structure, the Department of Electronic Engineering, School of Electronic Science and Engineering, Nanjing University The research conducted by Liu Xiaoyong in this area is as follows: the designed planar plasmonic waveguide device based on the symmetrical corrugated film structure realizes the coupling and output on two adjacent CSP boards. However, the analysis and analysis of the structure and related parameters involved in this patent are relatively small, and the experimental verification is only carried out in the microwave frequency band, which cannot prove that the same effect can be produced in the terahertz frequency band.

The waveguides of various structures proposed by Zhang Ying et al. in the article on terahertz pseudosurface plasmon subwavelength waveguides can only be verified to support terahertz transmission and effectively improve subwavelength localization and reduce transmission loss. , can not reach the versatility advantage mentioned in this patent.

D.Martin-Cano proposed the concept of the plasma waveguide of the domino structure in the domino plasma used in the sub-wavelength terahertz circuit. This article is based on the research and analysis of the concept of metamaterials, and it is concluded that the electromagnetic wave propagating on the surface The mode is not very sensitive to the width characteristics of the domino structure, and the super-strong electromagnetic wave confinement ability and low transmission loss can only show that it can effectively guide the transmission of terahertz in this structure, but cannot realize the transmission of terahertz in a certain frequency band.

Contents of the invention

In view of this, the purpose of the present invention is to provide a terahertz integrated device with an asymmetric curved structure, so that the transmission of terahertz can be realized without changing the structural geometric parameters of the device, and it has good robustness and versatility.

The present invention solves the above technical problems by the following technical means:

A terahertz integrated device with an asymmetric curved structure, including a substrate and a metal thin film horizontally arranged on the substrate. The side metal films on both sides of the central metal film are composed of side metal films. The side metal films are arc-shaped, and the opening is set toward the side away from the central metal film. The line connecting the curvature circle centers of the two side metal films and the center The included angle between the metal films is less than 90 degrees, and the two side walls of the central metal film and the side metal films are provided with regularly arranged sawtooth structures.

Further, the offset distance between the centers of the curvature circles of the two side metal films is 0.5mm-3mm.

Further, the minimum interval between the two adjacent metal films is 1 μm-5 μm.

Further, the zigzag structure has a width of 20 μm-50 μm, and a period length of 30 μm-60 μm.

Further, the metal thin film is made of gold or silver.

Beneficial effects of the present invention:

①The device has strong versatility and can still produce preset effects in different bands without changing the designed geometric structure, only need to change a few parameters in the design, the applicable range of the device will be expanded, and most terahertz band research.

②The robustness of the device is strong, and under the fluctuation of several parameters, it will not cause large-scale fluctuations in device performance, so the processing accuracy of the device is not high, and the processing cost is reduced.

Description of drawings

FIG. 1 is a schematic diagram of a surface plasmon waveguide provided by the background technology of the present invention;

Fig. 2 is an output simulation diagram of the surface plasmon waveguide in Fig. 1 provided by the background technology of the present invention;

Fig. 3 is a schematic structural view of a surface plasmon device with a three-layer three-dimensional structure provided by the background technology of the present invention;

Fig. 4 is a schematic structural diagram of a terahertz integrated device with an asymmetric curved structure provided by an embodiment of the present invention;

Fig. 5 is a terahertz optical path diagram of a terahertz integrated device with an asymmetric curved structure provided by an embodiment of the present invention;

Fig. 6 is a diagram of the coupling strength of the terahertz integrated device with the asymmetric curved structure in Fig. 5;

Fig. 7 is a curve diagram of energy transmission loss between waveguides of the terahertz integrated device of the asymmetric curved structure in Fig. 5;

Fig. 8 is a visualized propagation path diagram of surface plasmons on three waveguides in Fig. 5 .

Detailed ways

The present invention will be described in detail below in conjunction with accompanying drawing and specific embodiment:

As shown in FIG. 4 , an asymmetric curved terahertz integrated device of the present invention includes a substrate 4 and a metal thin film horizontally arranged on the substrate 4 , and the metal thin film is made of gold or silver. As shown in Figure 4, the metal film is provided with three pieces, which are composed of a linear central metal film located in the center and side metal films arranged on both sides of the central metal film. The central metal film is a horizontal waveguide 2, The side metal films on both sides are the left metal film and the right metal film respectively, the left metal film is the left waveguide 1, the right metal film is the right waveguide 3, the left metal film and the right waveguide The side metal films are all arc-shaped, and the openings are set towards the side away from the central metal film. The minimum distance between two adjacent metal films is 4 μm. The center of the curvature circle of the left metal film and the curvature circle of the right metal film The angle between the line connecting the center of the circle and the central metal film is less than 90 degrees, and the offset distance between the centers of the curvature circles of the two side metal films 3 is 0.5mm-3mm, and the central metal film and the side metal film Regularly arranged zigzag structures are arranged on both side walls of the zigzag structure, the width of the zigzag structure is 20 μm-50 μm, and the period length is 30 μm-60 μm.

As shown in Figure 4, assuming that there is a three-dimensional coordinate system in the space, surface plasmon polaritons (surface plasmon polaritons, SPPs) propagate to the right along the x-axis direction, and outside the SPPs waveguide, the evanescent field perpendicular to the propagation direction is Exponential decay, when the evanescent fields between two adjacent metal films overlap each other, energy exchange will occur between them at this time, and the energy will be transferred to the next metal film structure.

The normalized electric field of the metal film on the left side and the center metal film is written as:

Ψ ₁ (x,z)=u ₁ (z)exp(-iqx)(1)

Ψ ₂ (x,z)=u ₂ (z)exp(-iqx)(2)

Wherein, u ₁ (z), u ₂ (z) are the envelopes on the surface plasmons on the two metal layers of the left metal thin film and the central metal thin film, respectively. Decay rate of evanescent field where _εm is the dielectric constant of the material, ω is the frequency of the incident light, and the transmission constant a, d, h are the width, period and depth of the zigzag structure, respectively, and g is the interval between two adjacent metal films.

In the transmission direction (x-axis direction), Ψ ₁ (x, z), Ψ ₂ (x, z) must satisfy the Helmholtz equation. Based on the coupled mode theory, we can obtain the following form of Helmholtz with input source Z equation:

in ε _g is the dielectric constant of the metal film (gold).

Finally, the coupling formula between two metal films can be obtained:

Where c ₁₂ and c ₂₁ are the coupling coefficients:

From this form, the coupling formula between the three metal films can also be deduced as:

a ₁ , a ₂ , and a ₃ correspond to the electric field amplitudes of SPPs on the left metal film, the central metal film, and the right metal film, respectively.

The top view and terahertz optical path diagram of the terahertz integrated device with asymmetric curved structure designed by the present invention are shown in Figure 5. The thick black arrow represents the optical path of the incident terahertz light. Left waveguide 1, then coupling occurs between left waveguide 1 and center waveguide 2, after transmission, then coupled to right waveguide 3, and finally output in the direction indicated by the arrow.

The introduction of stimulated Raman adiabatic channels (STIRAP) is applied to the design of surface plasmon waveguides. This technology is widely used in the population transfer between energy levels. Due to the population transfer between energy levels and the coupling energy between waveguides The transfer is very similar, so in recent years, STIRAP technology has been widely used in the energy transfer between waveguides.

When the energy of the waveguide system evolves under adiabatic conditions, C ₂₃ >>C ₁₂ at the initial moment, and C ₂₃ <<C ₁₂ after a certain distance, such a coupling coefficient design can make all the energy initially injected into the left waveguide 1 transfer to the right waveguide 3.

In order to show the coupling effect more intuitively, give an example:

In this embodiment, the parameters are set as follows for the waveguide structure:

①The distance between the center of the curvature circle between the left waveguide 1 and the right waveguide 3 is δ=1.5mm

② Radius of curvature R = 45mm

③Horizontal waveguide length L=4mm

④The width of the zigzag structure a=40μm

⑤ Period of zigzag structure d=50μm

⑥The shortest distance interval between waveguides g=4μm

The calculated coupling strength plot is shown in Fig. 6.

As shown in Figure 7, according to the intensity diagram of SPPs, it can be seen that the energy transmission process between waveguides, in which the lossy curve under simulated actual conditions is slightly different from the curve under ideal conditions, but the overall trend is consistent. Figure 8 shows the visualized propagation paths of SPPs on three waveguides.

The above embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced. Without departing from the purpose and scope of the technical solutions of the present invention, all of them should be included in the scope of the claims of the present invention. The technologies, shapes and construction parts not described in detail in the present invention are all known technologies.

Claims (5)

1. a kind of Terahertz integrated device of asymmetry warp architecture, it is characterised in that: including substrate and be horizontally set on lining Metallic film on bottom, the metallic film are provided with three pieces, by centrally located linearly central metal film, and set The side metallic film composition in central metal film two sides is set, the side metallic film is in arc-shaped, and opening is directed away from Central metal film side setting, between the line and central metal film in the circle of curvature center of circle of two blocks of side metallic films Angle less than 90 degree, be provided with regularly arranged sawtooth on the two sidewalls of the central metal film and side metallic film Structure.

2. a kind of Terahertz integrated device of asymmetry warp architecture according to claim 1, which is characterized in that two pieces The offset distance in the circle of curvature center of circle of the side metallic film is 0.5mm-3mm.

3. a kind of Terahertz integrated device of asymmetry warp architecture according to claim 2, which is characterized in that described The minimum interval of two pieces of adjacent metal films is 1 μm -5 μm.

4. a kind of Terahertz integrated device of asymmetry warp architecture according to claim 3, which is characterized in that described The width of saw-tooth-type structures is 20 μm -50 μm, and cycle length is 30 μm -60 μm.

5. a kind of Terahertz integrated device of asymmetry warp architecture according to claim 4, which is characterized in that described The material of metallic film is gold or silver.