CN112433294B - Terahertz waveguide based on double negative curvature cladding structures - Google Patents

Abstract

The invention discloses a terahertz waveguide based on a double negative curvature cladding structure, which comprises an elliptical cladding tube area, a circular cladding tube area, a polymer cladding layer, a fiber core area; It is composed of 6 polymer structural units arranged in a ring at an equal interval of 60°; the circular cladding tube area is composed of 6 polymer structural units arranged in a ring at an equal interval of 60°; the oval tube and the circular tube unit are mutually structured. Connect the double negative curvature cladding regions that make up the waveguide. The polymer cladding layer acts as the cladding layer of the waveguide to achieve the geometric integrity of the entire waveguide structure. The terahertz wave is input from the hollow core of the waveguide, and through the interaction between the elliptical cladding tube area and the circular cladding tube area, the terahertz wave of a specific frequency can be effectively bound inside the waveguide core to realize the transmission function. The invention has the advantages of simple structure, high performance, low loss, easy processing and the like.

Description

Terahertz Waveguide Based on Double Negative Curvature Cladding Structure

technical field

The present invention relates to a terahertz waveguide with high transmission performance, in particular to a terahertz waveguide based on a double negative curvature cladding structure.

Background technique

Terahertz waves refer to electromagnetic waves with frequencies in the range of 0.1 to 10 THz (wavelength of 3000 to 30 μm), which overlap with millimeter waves in the long waveband and infrared light in the short waveband. It is the transition from macroscopic classical theory to microscopic quantum theory. The region is also the transition region from electronics to photonics, known as the "terahertz gap" of the electromagnetic spectrum. The band of terahertz waves can cover the characteristic spectrum of substances such as semiconductors, plasmas, organisms and biological macromolecules; using this band can deepen and expand human understanding of some basic scientific problems in physics, chemistry, astronomy, informatics and life sciences. know. Terahertz technology can be widely used in radar, remote sensing, homeland security and anti-terrorism, high-security data communication and transmission, atmospheric and environmental monitoring, real-time biological information extraction, and medical diagnosis. Therefore, THz research has great application value to the national economy and national security.

With the development of communication technology, the demand for various waveguides is also increasing. Compared with traditional waveguides, negative-curvature hollow-core waveguides have excellent characteristics such as flexible dispersion, lower loss, high nonlinearity, and high birefringence. It is widely used in the fields of communication, sensing, nonlinear optics and novel waveguide functional devices. Negative-curvature terahertz waveguides are currently a research hotspot, and designing negative-curvature terahertz waveguides with better transmission characteristics is of great significance for related applications of waveguides. Negative curvature means that the bending direction of the core boundary surrounded by the cladding tube is exactly opposite to the bending direction of the circular core. Since the negative curvature waveguide will cause the coupling effect of the cladding tube mode and the core mode when conducting terahertz waves, Therefore, the transmission loss of the waveguide is increased, so the size of the cladding tube of the negative-curvature terahertz waveguide needs to be strictly designed.

Negative curvature terahertz waveguides can usually reduce the corresponding transmission loss by increasing the number of nested rings or increasing or decreasing the number of cladding tubes. However, these methods are difficult to change the transmission loss of the waveguide in order of magnitude. Increasing the number of layers of cladding tubes in negative curvature waveguides is one of the effective ways to reduce transmission loss, and the design of two-layer cladding tubes can reduce losses by two orders of magnitude. In addition, published research results show that elliptical cladding tubes are more beneficial than circular cladding tubes to suppress the coupling of the waveguide's cladding-tube mode and the core mode, thereby further reducing losses.

In negative-curvature hollow-core waveguides, the core boundary with a small radius of curvature can reduce the loss of the negative-curvature hollow-core waveguides. The cladding structures of the current negative-curvature hollow-core waveguides are mostly circular hollow tube rings, but the size of the tube ring is not large. Blindly pursuing the core boundary with a small curvature radius, the advantages of the small curvature radius core boundary of the negative curvature hollow-core waveguide are not fully exerted. In the existing disclosed design scheme [CN110333571A], a structure using two layers of circular hollow tubes as the cladding is designed. This scheme uses glass as the substrate of the waveguide, and the size is small and can only be used in the mid-infrared band , cannot be used in the terahertz band. Moreover, using glass material or silicon material as the substrate increases the difficulty and cost of drawing, which is not conducive to practical application. Currently, there is a need for a high-performance double-clad tube negative-curvature terahertz hollow-core waveguide with low fabrication difficulty, large propagation bandwidth and low transmission loss in the terahertz band.

SUMMARY OF THE INVENTION

In order to overcome the deficiencies of the prior art, the present invention discloses a terahertz waveguide based on a double negative curvature cladding structure with a simple structure and high transmission performance. loss, suppress the generation of high-order modes, and at the same time solve the problem that the advantages of the small curvature radius of the core boundary are not fully utilized. In addition, the invention uses the organic polymer as the material, which is easy to realize the processing and manufacture of the waveguide, reduces the difficulty and saves the cost.

In order to achieve the above object, technical scheme of the present invention is as follows:

A terahertz waveguide based on a double negative curvature cladding structure, which includes an elliptical cladding tube, a circular cladding tube, a polymer cladding layer and a waveguide core region; in the cross section of the terahertz waveguide, 6 The elliptical cladding tubes are arranged in a circular equidistant space at 60° intervals to form an elliptical cladding tube area. One elliptical cladding tube and six circular cladding tubes are arranged staggered along the circumferential direction, and are connected to each other in the double negative curvature cladding area surrounding the synthetic waveguide; the waveguide core area is located inside the double negative curvature cladding area; The polymer cladding layer, as the outer cladding layer of the waveguide, is wrapped around the outside of the elliptical cladding tube area; the terahertz wave is input from the waveguide core area, and passes through the mutual interaction between the elliptical cladding tube area and the circular cladding tube area. As a result, the terahertz wave of a specific frequency is bound in the core region to realize the transmission function.

The above-mentioned technical scheme can adopt the following preferred ways:

Preferably, the long axis of the elliptical cladding tube is 1.6-2.0 mm, the short axis is 0.96-1.2 mm, and the tube wall thickness is 0.1 mm.

Preferably, the diameter of the circular cladding tube is 0.428-0.788 mm, and the thickness of the tube wall is 0.1 mm.

Preferably, the diameter of the core region is 1.172-1.4 mm.

Preferably, the substrate materials used for the elliptical cladding tube, the circular cladding tube and the polymer cladding layer are all polymer materials.

Further, the polymer material is Topas COC polymer material.

Further, the refractive index of the substrate material used in the elliptical cladding tube, the circular cladding tube and the polymer cladding layer is 1.5258.

Preferably, in the double negative curvature cladding region, adjacent elliptical cladding tubes and circular cladding tubes are connected to each other in such a manner that the outer circumference is tangent, and the spacing is zero.

Preferably, in the cross section of the terahertz waveguide, the inner circumference of the polymer cladding layer, the centers of the six elliptical cladding tubes, and the centers of the six circular cladding tubes are respectively located on three concentric circles, and the six The long axes of the elliptical cladding tubes are all along the radial direction of the concentric circles.

Preferably, the entire terahertz waveguide structure is fabricated by 3D printing technology.

Owing to having adopted the above-mentioned technical scheme, the technical progress that the present invention obtains is:

1. The present invention has a simple structure, consisting of only 6 elliptical tubes and 6 circular tubes, and proposes a negative curvature waveguide with a double negative curvature cladding structure for the first time in the terahertz frequency band.

2. The invention has excellent transmission performance in the working frequency band, single material and high production efficiency.

3. In the structure of the present invention, using the double anti-resonance effect of the elliptical tube and the circular tube, the terahertz wave is confined in the core region, which greatly reduces the confinement loss of the terahertz waveguide. The first anti-resonance effect of the elliptical tube is used to confine the terahertz wave to the core region; while the second anti-resonance effect of the circular tube further reduces the leakage of the terahertz wave energy.

Description of drawings

Figure 1 is a schematic diagram of the cross-sectional structure of a terahertz waveguide based on a double negative curvature cladding;

Fig. 2 is the structural unit of the elliptical cladding tube and the circular cladding tube of the terahertz waveguide based on the double negative curvature cladding;

Fig. 3 is the loss spectrum of the terahertz waveguide based on the double negative curvature cladding structure;

Detailed ways

In order to make the technical solutions, advantages and purposes of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

As shown in Figures 1-2, an embodiment of the present invention provides a terahertz waveguide structure based on double negative curvature cladding, which includes an elliptical cladding tube 1, a circular cladding tube 2, a polymer cladding tube Cladding 3 and waveguide core region 4. In the cross-section of the terahertz waveguide shown in Fig. 1, six elliptical cladding tubes 1 are arranged in an equidistant annular manner with an interval of 60° (ie, a central angle of 60°) to form an elliptical cladding tube region, and six circular cladding tubes 1 The cladding tubes 2 are arranged in a circular equidistant manner at an interval of 60° (ie, the central angle of the circle is 60°) to form a circular cladding tube area, and the 6 elliptical cladding tubes 1 and the 6 circular cladding tubes 2 are arranged in the circumferential direction. Staggered arrangement, that is, both sides of each oval cladding tube 1 are circular cladding tubes 2 , and both sides of each circular cladding tube 2 are also oval cladding tubes 1 . Therefore, viewed from the cross section, 12 cladding tubes are connected to each other in the double negative curvature cladding region of the closed end-to-end enclosed synthetic waveguide. The waveguide core region 4 is located in the center of the interior of the double negative curvature cladding region, which can be equivalently regarded as the circular dotted line region in FIG. 1 . The polymer cladding layer 3 is used as the outer cladding layer of the entire waveguide, and is attached and wrapped around the outside of the elliptical cladding tube region, so as to realize the geometric integrity of the entire waveguide structure. When the waveguide is in use, the terahertz wave is input from the waveguide core region 4 and passes through the interaction between the elliptical cladding tube region and the circular cladding tube region, so that the terahertz wave of a specific frequency is bound in the core region 4 , to realize the transmission function.

In the above terahertz waveguide structure, the design parameters and materials of each structural component can be selected as follows: the long axis of the elliptical cladding tube 1 is 1.6-2.0 mm, the short axis is 0.96-1.2 mm, and the tube wall thickness is 0.1 mm.

The diameter of the circular cladding tube 2 is 0.428-0.788 mm, and the thickness of the tube wall is 0.1 mm. The diameter of the core region 4 is 1.172 to 1.4 mm. The substrate materials used for the oval cladding tube 1, the circular cladding tube 2 and the polymer cladding layer 3 are all polymer materials, including but not limited to Topas COC polymer materials, other similar polymer materials Also applies to this technique. The refractive index of the substrate material used for the elliptical cladding tube 1, the circular cladding tube 2 and the polymer cladding layer 3 was 1.5258. In the double negative curvature cladding region, the adjacent elliptical cladding tubes 1 and circular cladding tubes 2 are connected to each other in a tangential manner on the outer periphery, and the spacing is 0, as shown in FIG. 2 . In addition, in the cross section of the terahertz waveguide, the six centers of the six elliptical cladding tubes 1 are located on a circle, and the six centers of the six circular cladding tubes 2 are also located on a circle, so the polymer cladding The inner circumference of layer 3, the centers of the six elliptic cladding tubes 1, and the centers of the six circular cladding tubes 2 are respectively located on three concentric circles, and the long axes of the six elliptic cladding tubes 1 are all along the concentric circles. The radial direction of a circle, that is, the straight line where the long axis passes through the center of the concentric circles.

The entire terahertz waveguide structure is processed and fabricated by 3D printing technology, so the present invention has the advantages of simple structure, high transmission performance, low loss, and easy processing.

Example 1

In this embodiment, the shapes of the components of the terahertz waveguide structure based on the double negative curvature cladding are as described above, that is, FIG. 1 and FIG. 2 , and thus will not be repeated here. However, the design parameters and materials of each structural component are as follows:

The long axis of the elliptical cladding tube is 1.8mm, the short axis is 0.96mm, and the wall thickness is 0.1mm, that is, the ratio of the long axis to the short axis of the elliptical cladding tube is approximately 1.9. The diameter of the circular cladding tube is 0.6 mm, and the thickness of the tube wall is 0.1 mm. The diameter of the waveguide hollow core region is 1.4 mm. The substrate material used for the elliptical cladding tube, the circular cladding tube and the polymer cladding layer was Topas COC polymer with a refractive index n of 1.5258. In the double negative curvature cladding area, the adjacent elliptical cladding tubes 1 and the circular cladding tubes 2 are connected to each other in a manner of tangent to the outer periphery, and the spacing is 0. In the cross section of the terahertz waveguide, the six centers of the six elliptical cladding tubes 1 are located on a circle, and the six centers of the six circular cladding tubes 2 are also located on a circle, so the polymer cladding layer 3 The inner circumference of the 6 elliptical cladding tubes 1 and the centers of the 6 circular cladding tubes 2 are located on three concentric circles with gradually decreasing diameters. The long axes of the six elliptical cladding tubes 1 are all along The radial direction of the concentric circle, that is, the line where the long axis is located passes through the center of the concentric circle. Terahertz waves of specific frequencies are input from the core region, and under the interaction of the elliptical cladding tubes and the circular cladding tubes, the terahertz waves of specific frequencies are effectively bound in the core region. The waveguide structure of this embodiment can be processed and manufactured by the existing 3D printing technology.

As shown in Fig. 3, the confinement losses of the terahertz waveguide based on the double negative curvature cladding structure provided in this embodiment are 3.2× ^10-3 dB at 2.0THz, 2.1THz, 2.2THz, 2.3THz and 2.44THz, respectively /cm, 1.8 x 10 ^-3 dB/cm, 1.4 x 10 ^-4 dB/cm, 1.8 x 10 ^-5 dB/cm, and 3.2 x 10 ^-6 dB/cm. Therefore, it is shown that the present invention utilizes the double anti-resonance effect of the elliptical tube and the circular tube, so that the terahertz wave is confined in the core region, which can greatly reduce the confinement loss of the terahertz waveguide.

Claims (10)

1. A terahertz waveguide based on a double negative curvature cladding structure, characterized in that it comprises an elliptical cladding tube (1), a circular cladding tube (2), a polymer cladding layer (3) and a waveguide fiber The core area (4); in the cross section of the terahertz waveguide, six elliptical cladding tubes (1) are arranged in a circular equidistant interval of 60° to form an elliptical cladding tube area, and six circular cladding tubes (2) A circular cladding tube area is formed by arranging 60° annularly at equal intervals, and the 6 elliptical cladding tubes (1) and the 6 circular cladding tubes (2) are staggered along the circumferential direction and mutually connecting the double negative curvature cladding regions surrounding the synthetic waveguide at the head and tail; the waveguide fiber core region (4) is located inside the double negative curvature cladding region; the polymer cladding layer (3) serves as the outer cladding layer of the waveguide, wrapping Outside the elliptical cladding tube area; the terahertz wave is input from the waveguide core area (4), and through the interaction between the elliptical cladding tube area and the circular cladding tube area, the terahertz wave of a specific frequency is bound in the fiber In the core area (4), the transmission function is realized. 2. The terahertz waveguide based on the double negative curvature cladding structure according to claim 1, characterized in that the long axis of the elliptical cladding tube (1) is 1.6-2.0 mm, and the short axis is 0.96-1.2 mm , the wall thickness is 0.1mm. 3. The terahertz waveguide based on the double negative curvature cladding structure according to claim 1, characterized in that the diameter of the circular cladding tube (2) is 0.428-0.788 mm, and the thickness of the tube wall is 0.1 mm. 4. The terahertz waveguide based on the double negative curvature cladding structure according to claim 1, characterized in that the diameter of the core region (4) is 1.172-1.4 mm. 5. The terahertz waveguide based on the double negative curvature cladding structure according to claim 1, characterized in that the elliptical cladding tube (1), the circular cladding tube (2) and the polymer cladding layer (3) The substrate materials used are all polymer materials. 6 . The terahertz waveguide based on the double negative curvature cladding structure according to claim 5 , wherein the polymer material is a Topas COC polymer material. 7 . 7. The terahertz waveguide based on the double negative curvature cladding structure according to claim 5, characterized in that the elliptical cladding tube (1), the circular cladding tube (2) and the polymer cladding layer (3) The refractive index of the substrate material used was 1.5258. 8. The terahertz waveguide based on the double negative curvature cladding structure according to claim 1, characterized in that in the double negative curvature cladding region, adjacent elliptical cladding tubes (1) and circular cladding The tubes (2) are connected to each other in a tangential manner on the outer periphery, and the spacing is 0. 9. The terahertz waveguide based on the double negative curvature cladding structure according to claim 1, characterized in that in the cross section of the terahertz waveguide, the inner circumference of the polymer cladding layer (3), 6 elliptical shapes The center of the cladding tube (1) and the centers of the six circular cladding tubes (2) are respectively located on three concentric circles, and the long axes of the six oval cladding tubes (1) are all along the diameter of the concentric circles Towards. 10 . The terahertz waveguide based on the double negative curvature cladding structure according to claim 1 , wherein the entire terahertz waveguide structure is fabricated by 3D printing technology. 11 .

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