A terahertz anti-resonant fiber capable of realizing ultra-low transmission loss

Abstract

The present application relates to a kind of terahertz anti-resonance optical fibers, specifically to a kind of terahertz anti-resonance optical fibers capable of realizing ultra-low transmission loss, 9 concentric nested tubes are arranged in the cladding of the optical fiber, solid support rods are arranged in the ring cavity of the concentric nested tubes, and a protective tube is arranged outside the cladding of the concentric nested tubes;The inner radius R of the optical fiber is 5.5 mm, the diameter D of the core thereof is 6.2 mm;The outer diameter d1 of the outer sleeve of the concentric nested tube is 2.4 mm, the outer diameter d2 of the inner sleeve thereof is 1.5 mm, and the thickness t of the outer sleeve and the inner sleeve is 0.35 mm;The thickness T1 of the protective tube is 0.15 mm, the thickness T of the perfect matching layer outside the protective tube is 0.5 mm;The base material of the terahertz anti-resonance optical fiber is high-resistance silicon.By increasing the core diameter and increasing the number of cladding nested tubes, a kind of anti-resonance optical fiber with 9 double-layer concentric circular nested tube structure is designed, which can effectively reduce the confinement loss.

Description

Technical Field

[0001] This invention relates to a terahertz anti-resonant optical fiber, specifically to a terahertz anti-resonant optical fiber capable of achieving ultra-low transmission loss. Background Technology

[0002] Hollow-core optical fibers (HCFs), as a type of special optical fiber, possess advantages such as low optical nonlinearity, low waveguide dispersion, low material absorption, high damage threshold, and low transmission delay. They are widely used in high-power transmission, high-speed data communication, ultrashort pulse transmission, pulse compression, supercontinuum media, gas fiber lasers, and gas nonlinear optics. Hollow-core optical fibers mainly include hollow-core photonic bandgap fiber (HC-PBGF) and hollow-core antiresonant fiber (HC-ARF). HC-PBGF utilizes the photonic bandgap effect to tightly confine light to the core region by periodically arranged cladding, and transmission loss can be reduced by adjusting the cladding structure. However, the transmission bandwidth of HC-PBGF is typically relatively limited, while HC-ARF can effectively overcome this bandwidth limitation and simultaneously possesses transmission characteristics such as low nonlinearity, low transmission loss, and negligible dispersion, thus attracting widespread attention.

[0003] HC-ARF achieves light transmission by suppressing coupling between the core mode and cladding mode through anti-resonance effects, and can operate in the near-infrared, mid-infrared, and terahertz bands. To achieve low-loss transmission in HC-ARF, researchers have designed various novel anti-resonant fiber structures using different fiber materials. However, due to the unique characteristics of the terahertz band, the reported losses of anti-resonant fibers are all relatively high. V. Setti et al. fabricated a terahertz anti-resonant fiber composed of six single-layer cylindrical tubes using PMMA material and measured its total loss at 0.828 THz to be 16 dB / m. GKM Hasanuzzaman et al. designed a terahertz anti-resonant fiber based on six nested cylindrical tubes using Topas material, achieving a total loss of 0.05 dB / m at 1 THz, with a confinement loss of only 3.4307 × 10⁻⁶. −4 dB / m, effective material loss has a significant impact on total loss, and the two are almost equal. Low-loss transmission bandwidth (<10) -1 The total loss (dB / m) is 0.4 THz. A. Mollah et al. designed a terahertz antiresonant fiber using Zeonex material, consisting of six semicircular and semielliptical tubes connected together. Simulation results show that the total loss at 1 THz is 0.034 dB / m, where the confined loss is within 10 dB / m. −4The loss is on the order of dB / m, with an effective material loss of 0.034 dB / m. The low-loss transmission bandwidth is 0.5 THz. J. Sultana et al. used Zeonex material to study three types of terahertz antiresonant fibers, comparing and analyzing the performance of unnested, nested, and adjacent nested tubes. They found that the loss of five nested tubes was relatively low, and the total loss at 1 THz was 0.055 dB / m. The study found that the main factor affecting the total loss of terahertz antiresonant fibers is that the effective material loss was not effectively reduced. Summary of the Invention

[0004] To further address the aforementioned limitation loss problem, this invention provides a terahertz antiresonant fiber capable of achieving ultra-low transmission loss. By increasing the core diameter and the number of nested cladding tubes, an antiresonant fiber with a structure of nine double-layer concentric nested tubes was designed, which effectively reduces limitation loss.

[0005] The technical solution adopted in this invention is as follows: a terahertz anti-resonant optical fiber capable of achieving ultra-low transmission loss. The cladding of the terahertz anti-resonant optical fiber contains nine circumferentially distributed concentric nested tubes. A solid support rod is provided within the annular cavity between the inner and outer sleeves of the concentric nested tubes. A protective tube is provided outside the cladding. The inner radius R of the terahertz anti-resonant optical fiber is 5.5 mm, and its core diameter D is 6.2 mm. The outer diameter d1 of the outer sleeve of the concentric nested tube is 2.4 mm, and the outer diameter d2 of the inner sleeve is 1.5 mm. The thickness t of the outer and inner sleeves is 0.35 mm. The thickness T1 of the protective tube is 0.15 mm, and the thickness T of the perfectly matched layer outside the protective tube is 0.5 mm. The substrate material of the terahertz anti-resonant optical fiber is high-resistivity silicon.

[0006] Furthermore, the concentric nested tubes are evenly distributed around the center of the fiber core.

[0007] The beneficial effects of this invention are: it provides a terahertz antiresonant fiber capable of achieving ultra-low transmission loss. By increasing the core diameter and the number of cladding nested tubes, an antiresonant fiber with a structure of nine double-layer concentric nested tubes was designed, which effectively reduces confinement loss. The confinement loss at 1 THz is only 2.6 × 10⁻⁶. -4 dB / m, while the effective material loss is reduced to 2.3 × 10⁻⁶ dB / m by using HRS material. -4 dB / m, bringing the total loss down to 10 for the first time. −4The results are on the order of dB / m and are achievable in the ranges of 0.88–0.92 THz and 0.96–1.14 THz. Furthermore, the effect of bending on loss was investigated; with a bending radius greater than 60 cm, the bending loss at 1 THz remains below 7.3 × 10⁻⁶. -3 dB / m. Compared to existing technologies, it exhibits superior robust transmission characteristics and has high commercial value. Anti-resonant fiber demonstrates even better robust transmission characteristics compared to existing technologies. Anti-resonant fiber not only effectively reduces effective material loss but also controls confinement loss, ultimately achieving a total loss as low as 10 dB / m. −4 With values ​​in the dB / m range, it exhibits exceptional transmission performance. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the cross-section of a terahertz anti-resonant fiber;

[0009] Figure 2 It is a graph showing the effect of the wall thickness t of the outer and inner sleeves of the concentric nested tubes on the limiting loss.

[0010] Figure 3 It is a graph showing the effect of the wall thickness t of the outer and inner sleeves of the concentric nested tubes on the effective material loss.

[0011] Figure 4 It is a graph showing the effect of the wall thickness t of the outer and inner sleeves of the concentric nested tubes on the total loss.

[0012] Figure 5 It is a contour plot of the minimum total loss electric field for the outer and inner sleeves of the concentric nested tubes at different thicknesses t;

[0013] Figure 6 This is a graph showing the effect of the outer diameter d1 of the outer tube of the concentric nested tube on the total loss spectrum.

[0014] Figure 7 This is a graph showing the effect of the outer diameter d1 of the outer sleeve of the concentric nested tube on the limiting loss, effective material loss, and total loss when the operating frequency is 1 THz.

[0015] Figure 8 This is a graph showing the effect of the outer diameter d2 of the inner sleeve of the concentric nested tubes on the total loss spectrum.

[0016] Figure 9 This is a graph showing the effect of the outer diameter d2 of the inner sleeve of the concentric nested tube on the limiting loss, effective material loss, and total loss when the operating frequency is 1 THz.

[0017] Figure 10 This is a graph showing the effect of the number of concentric nested tubes on the total loss spectrum.

[0018] Figure 11 This is a bending loss diagram at different bending radii when the anti-resonant fiber is bent along the positive x-axis with an operating frequency of 1 THz and the number of concentric nested tubes is 8 and 9.

[0019] Figure 12 The bending loss spectrum of the anti-resonant fiber under different bending radii is when the number of concentric nested tubes is 9 and the fiber is bent along the positive x-axis.

[0020] Figure 13 The diagram shows the bending loss of an anti-resonant fiber with a working frequency of 1 THz, 8 and 9 concentric nested tubes, and different bending radii when the fiber is bent in the opposite direction along the x-axis.

[0021] Figure 14 The number of concentric nested tubes is 9. The bending loss spectrum of the anti-resonant fiber under different bending radii when it bends in the opposite direction along the x-axis. Detailed Implementation

[0022] like Figure 1 As shown, a terahertz anti-resonant fiber capable of achieving ultra-low transmission loss is disclosed. The terahertz anti-resonant fiber has nine concentrically nested tubes 1 evenly distributed around its cladding. A solid support rod 5 is located within the annular cavity between the inner and outer sleeves of each concentrically nested tube 1. A protective tube 2 is located outside the cladding. The inner radius R of the terahertz anti-resonant fiber is 5.5 mm, and the diameter D of its core 4 is 6.2 mm. The outer diameter d1 of the outer sleeve of the concentrically nested tube 1 is 2.4 mm, and the outer diameter d2 of its inner sleeve is 1.5 mm. The thickness t of both the outer and inner sleeves is 0.35 mm. The thickness T1 of the protective tube 2 is 0.15 mm, and the thickness T of the perfectly matched layer 3 outside the protective tube 2 is 0.5 mm. The substrate material of the terahertz anti-resonant fiber is high-resistivity silicon. The concentrically nested tubes 1 are evenly distributed around the center of the core 4.

[0023] like Figure 2 and Figure 3 As shown, when the structural parameters of the antiresonant fiber are R = 5.5 mm, T1 = 0.15 mm, D = 6.2 mm, d1 = 2.4 mm, and d2 = 1.5 mm, the confinement loss spectrum under different wall thicknesses t is as follows. Figure 2 As shown. When t = 0.05 mm, the low-loss bandwidth of the loss spectrum is limited (<10). -1 The narrowest and lowest limiting loss (dB / m) is 1.4 × 10⁻⁶. -3dB / m. As the wall thickness t decreases, the loss spectrum gradually shifts towards higher frequencies, the loss gradually decreases, and the low-loss bandwidth gradually widens. This is because the smaller the wall thickness of the concentric nested tubes, the higher the corresponding resonant frequency and the wider the low-loss region. When t = 0.035 mm, the low-loss region of the confinement loss spectrum is the widest, and the lowest confinement loss is 2.5 × 10⁻⁶ dB / m. -4 dB / m. Effective material loss spectra at different wall thicknesses t are as follows: Figure 3 As shown, with decreasing wall thickness t, the loss spectrum gradually shifts towards higher frequencies, the low-loss frequency range gradually expands, and the minimum loss gradually decreases, with the minimum effective material loss being 2.3 × 10⁻⁶. -4 dB / m.

[0024] like Figure 4 and Figure 5 As shown, the total loss spectrum for different wall thicknesses t can be obtained by superimposing the constraint loss and the effective material loss. Figure 4 As shown, the minimum total loss gradually decreases with increasing thickness t. Figure 5 The electric field contour plots for the lowest total loss at different thicknesses t are shown. It can be seen that when t = 0.035 mm, the electric field is better confined to the fiber core region, and the total loss is also the lowest at this point, only 4.8 × 10⁻⁶. -4 dB / m. Meanwhile, below 10 -1 The low-loss bandwidth (dB / m) also increases with increasing thickness (t), reaching 0.48 THz when t = 0.035 mm, which is below 10 THz. -3 The frequency range of dB / m also reaches 0.22 THz. It can be seen that the use of HRS material and a nine-concentric nested tube structure in the terahertz band can effectively reduce the transmission loss of anti-resonant optical fiber and achieve the requirement of high bandwidth and low loss transmission.

[0025] like Figure 6 and Figure 7 As shown, when R = 5.5 mm, T1 = 0.15 mm, d2 = 1.5 mm, and t = 0.035 mm, the effect of the outer diameter d1 of the outer tube of the concentric nested tube on the total loss spectrum of the anti-resonant fiber is as follows. Figure 6 As shown, the outer diameter of the outer sheath has a relatively small impact on the loss spectrum. When d1 = 2 mm, the anti-resonant fiber has the narrowest low-loss bandwidth and the largest minimum loss. With increasing d1, the loss spectra of the three types within the low-loss bandwidth are relatively similar when d1 = 2.2 mm, d1 = 2.4 mm, and d1 = 2.6 mm. To further clarify the optimal d1, Figure 7The confinement loss, effective material loss, and total loss are presented at 1 THz for different outer tube diameters. The confinement loss decreases rapidly initially with increasing d1, then increases slowly. This is because when d1 is small, the spacing between adjacent tubes is large, and light easily leaks through the gaps, as shown in the electric field illustration a, resulting in higher losses. As d1 increases, the electric field is better confined to the fiber core region, as shown in illustrations b and c. When d1 continues to increase, the spacing between adjacent tubes becomes smaller, leading to additional resonance between tubes and a slight increase in loss, but the effect on the loss spectrum is no longer significant. Compared to the confinement loss, the outer tube diameter has a smaller impact on the effective material loss, as shown by solid line 2. Solid line 3 shows the total loss; the total loss is lowest when d1 = 2.4 mm.

[0026] like Figure 8 and Figure 9 As shown, when R = 5.5 mm, T1 = 0.15 mm, D = 6.2 mm, d1 = 2.4 mm, and t = 0.035 mm, the effect of the outer diameter d2 of the inner sleeve of the concentric nested tube on the total loss spectrum of the anti-resonant fiber is as follows. Figure 8 As shown in the figure. It can be seen that when the outer diameter of the inner sleeve is small (d2 = 0.5 mm), the minimum loss is slightly higher, at 1.4 × 10⁻⁶. -3 dB / m, but when d2 increases to d2=1.0 mm, the minimum loss decreases, and the difference in the loss spectrum is small with further increases in d2. This is because when the outer diameter of the inner sleeve of the concentric nested tube is small, a second anti-resonant layer cannot be formed; only when d2 is large can a double-layer anti-resonant effect be formed to confine the electric field to the fiber core region. To further determine the optimal d2, Figure 9 The confinement loss, effective material loss, and total loss are given for different inner tube outer diameters at 1 THz. It can be seen that d2 has almost no effect on the effective material loss, but has a certain impact on the confinement loss. The solid line (number 3) represents the total loss. The inset shows the electric field contour plots for different d2 values. It is evident that when d2 = 1.5 mm, the electric field is better confined to the fiber core region, and the total loss corresponds to the lowest value. Therefore, d2 = 1.5 mm is chosen as the optimal value.

[0027] like Figure 10 As shown, when R = 5.5 mm, T1 = 0.15 mm, D = 6.2 mm, d1 = 2.4 mm, d2 = 1.5 mm, and t = 0.035 mm, the total loss spectrum and the electric field contour plot at 1 THz for different numbers of nested tubes are as follows. Figure 10 As shown in the diagram, when the number of concentric nested tubes is 6, the electric field is not confined to the fiber core region due to the large spacing between adjacent tubes, resulting in partial leakage and the highest total loss. As shown in the electric field illustration (a), the lowest value of its loss spectrum is as high as 1.3 × 10⁻⁶. -2dB / m. When the number of concentric nested tubes increases to 7, the spacing between adjacent tubes decreases, and the electric field leakage decreases. As shown in the electric field illustration (b), the lowest value of the loss spectrum is 1.6 × 10⁻⁶. -3 dB / m. When the number of concentric nested tubes increases to 8 and 9, the electric field contour plots of c and d are basically the same, indicating that the electric field is effectively confined to the fiber core region. Their loss spectra are also basically the same, suggesting that when the number of concentric nested tubes is 8 and 9, due to the large number of tubes, the electric field is unlikely to leak through the gaps, and both can...

[0028] Effective control of the total loss of antiresonant optical fiber enables low-loss transmission.

[0029] like Figures 11-14 As shown, due to the asymmetric nature of the nine concentric nested tube structures, Figure 11 and Figure 13 The bending loss at 1 THz is given for 8 and 9 nested tubes, with bending angles of 0° (positive x-axis) and 180° (negative x-axis), under different bending radii. It is evident that the anti-resonant fiber with 9 concentric nested tubes exhibits lower overall bending loss and better bending resistance. Therefore, 9 concentric nested tubes are selected as the optimal anti-resonant fiber structure, and its bending characteristics are further analyzed. When the anti-resonant fiber bends, the electric field in the core region deviates radially towards the bending radius. When the bending radius R... b Even at larger values, the electric field is still well confined to the fiber core region, such as Figure 11 and Figure 13 The electric fields in insets a and b are shown. However, as the bending radius continues to decrease, the bending loss gradually increases and a loss peak appears. The electric field diagram at the loss peak (as shown in insets c and d) indicates that the core electric field has partially leaked into the cladding region. This is because resonance occurs when the core mode and cladding mode are phase-matched, leading to an increase in bending loss.

[0030] Figure 12 and Figure 14 The effect of bending on the loss spectrum of a nine-concentric nested anti-resonant fiber is presented at bending angles of 0° (positive x-direction) and 180° (negative x-direction). When the bending radius R... b At 22 cm, all bending losses are greater than 10. -1 dB / m. This is because bending disrupts the symmetry of the antiresonant fiber, significantly distorting the ideal refractive index distribution and increasing confinement loss compared to straight fibers. As the bending radius increases to R... bAt a bending radius of 30 cm, bending loss decreases, and a low-loss region emerges. The larger the bending radius, the wider the low-loss region. When the bending radius approaches infinity, the low-loss bandwidth is the widest, and the loss is the lowest. Compared to existing work, antiresonant fiber exhibits better robust transmission characteristics. Table 1 also compares the transmission performance of antiresonant fiber with existing antiresonant fiber methods. Compared to existing work, antiresonant fiber not only effectively reduces effective material loss but also controls confinement loss, ultimately achieving a total loss as low as 10%. −4 With values ​​in the dB / m range, it exhibits exceptional transmission performance.

[0031] Table 1

[0032]

[0033] By optimizing the physical parameters, the effects of wall thickness, outer layer diameter, inner layer diameter, and number of tubes on optical fiber transmission performance were analyzed in detail using the finite element method. The analysis results show that the total loss of this antiresonant fiber operating at 1 THz is as low as 4.9 × 10⁻⁶. -4 The proposed antiresonant fiber achieves a low-loss transmission bandwidth of 0.48 THz within the 0.6–1.4 THz range, with a bending loss of dB / m. Furthermore, calculations of the bending loss at 1 THz show that, even with a bending radius greater than 60 cm, the bending loss remains below 7.3 × 10⁻⁶ dB / m. -3 dB / m, demonstrating good robust transmission performance.

[0034] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention and should not be construed as limiting the invention to the specific implementations described above. Without departing from the overall concept and protection of the claims, several simple deductions or substitutions can be made, all of which should be considered within the scope of protection of the present invention.

Claims

1. A terahertz anti-resonant optical fiber capable of achieving ultra-low transmission loss, characterized in that: The cladding of the terahertz anti-resonant fiber is provided with nine concentric nested tubes (1) evenly distributed around the circumference. A solid support rod (5) is provided in the annular cavity between the inner and outer sleeves of the concentric nested tubes (1). A protective tube (2) is provided on the outside of the cladding. The inner radius R of the terahertz anti-resonant fiber is 5.5 mm, and the diameter D of its core (4) is 6.2 mm. The outer diameter d1 of the outer sleeve of the concentric nested tube (1) is 2.4 mm, the outer diameter d2 of its inner sleeve is 1.5 mm, and the thickness t of the outer sleeve and the inner sleeve is 0.35 mm. The thickness T1 of the protective tube (2) is 0.15 mm, and the thickness T of the perfect matching layer (3) outside the protective tube (2) is 0.5 mm. The substrate material of the terahertz anti-resonant fiber is high-resistivity silicon.

2. The terahertz anti-resonant optical fiber capable of achieving ultra-low transmission loss according to claim 1, characterized in that: The concentric nested tubes (1) are evenly distributed around the center of the fiber core (4).

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