Anti-resonance hollow-core optical fiber with communicated cavity structure

Abstract

The invention discloses an anti-resonance hollow-core optical fiber with a communicated cavity structure. The anti-resonance hollow-core optical fiber comprises a hollow core (101); a plurality of main anti-resonance tubes (102) distributed around the hollow core; and an outer cladding (301) surrounding the main anti-resonant tube, the outer cladding having an inner wall (301a). At least one cavity structure (201) is embedded in the solid material area of the outer cladding, the cavity structure is located at the corresponding position between the adjacent main anti-resonance tubes, and the front wall (201a) of the cavity structure and the inner wall (301a) of the outer cladding are separated by a continuous solid material layer to form an anti-resonance layer. At least one micro-channel (401) is arranged in the outer cladding, and the micro-channel is communicated with an air area defined by the cavity structure and the inner wall of the outer cladding and / or the outer surface of the optical fiber; the minimum transverse size of the micro-channel is smaller than the working wavelength, an optical cut-off channel is formed for the working wavelength, gas communication and air pressure self-adaptive balance are achieved, meanwhile, leakage of a light field along the micro-channel is restrained, and limiting loss is reduced.

Description

Technical Field

[0001] This invention relates to the field of optical fiber devices and optical transmission technology, specifically to an anti-resonant hollow-core optical fiber, and more particularly to an anti-resonant hollow-core optical fiber in which a subwavelength microchannel is set in a cavity structure embedded in the outer cladding, so that the cavity structure is connected to the air region defined by the inner wall of the outer cladding and / or the outer surface of the optical fiber, thereby achieving dynamic balance of air pressure and gas introduction while suppressing optical field leakage and reducing confinement loss. Background Technology

[0002] Antiresonant hollow fiber utilizes a thin-walled antiresonant structure to strongly reflect transversely leaked light, thus confining the optical field primarily within the hollow core. Compared to traditional solid-core fiber, antiresonant hollow fiber offers advantages such as weak nonlinear effects, controllable dispersion, and low latency, making it suitable for applications in high-speed optical communication, high-power laser transmission, broadband transmission, and sensing.

[0003] Double-nested antiresonant nodeless fiber (DNANF) is a typical structure. By introducing one or more nested antiresonant tubes inside the main antiresonant tube and adopting a nodeless design, glass guided mode coupling can be suppressed and confinement loss reduced, achieving low transmission loss and superior mode field quality in the near-infrared communication band. In recent years, DNANF structures have been developing towards standard single-mode fiber outer diameter and mode field matching. GhafourAmouzad Mahdiraji et al. reported at ECOC 2024 (the 50th European Optical Communication Conference) a hollow-core DNANF with an outer diameter and mode field diameter matching standard single-mode fiber, exhibiting O-band and C-band losses below 2 dB / km, and possessing effective single-mode and bending resistance characteristics, demonstrating the application potential of this type of structure under small outer diameter (e.g., 125µm) conditions.

[0004] In antiresonant hollow-core optical fibers, the optical field easily leaks into the cladding region along the gap direction due to the lack of a sufficient antiresonant barrier between adjacent main antiresonant tubes, leading to increased loss. This gap leakage problem is prevalent in various antiresonant hollow-core optical fiber structures, and is more prominent under structural parameters such as small outer diameter, thin walls, and small gaps.

[0005] To address this issue, a cavity structure can be embedded within the solid material of the outer cladding layer at a corresponding position in the gap between adjacent main anti-resonant tubes. This creates an additional anti-resonant layer between the solid material layer on the front wall of the cavity and the inner wall of the outer cladding layer, suppressing optical field leakage in the gap direction and reducing confinement loss. However, if the cavity structure is designed as a sealed form that is not connected to the air region defined by the inner wall of the outer cladding layer, pressure differences may arise between the inside and outside during wire drawing and subsequent use due to factors such as temperature changes and changes in ambient air pressure. This can lead to stress accumulation, local deformation, or even failure of the structure. Furthermore, a sealed cavity is not conducive to introducing external gas into the cavity or hollow core region for gas sensing and environmental monitoring.

[0006] Using a large-sized connecting channel directly can easily cause optical field leakage along the channel and introduce additional losses, making it difficult to achieve both connectivity and low loss. Therefore, it is necessary to provide an anti-resonant hollow fiber structure that can achieve adaptive pressure balance and gas introduction while maintaining cavity leakage suppression. Summary of the Invention

[0007] The purpose of this invention is to provide an anti-resonant hollow-core optical fiber with a connected cavity structure. By setting a subwavelength microchannel in the cavity structure embedded in the outer cladding, the cavity structure is connected to the air region defined by the inner wall of the outer cladding and / or the outer surface of the optical fiber, thereby achieving adaptive pressure balance and gas introduction during fiber drawing and use. At the same time, the optical cutoff characteristics of the microchannel are used to suppress light field leakage along the channel, reducing confinement loss while maintaining connectivity.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: an anti-resonant hollow-core optical fiber with a connected cavity structure, comprising a hollow core (101), a plurality of main anti-resonant tubes (102), an outer cladding (301), and at least one cavity structure (201) completely embedded in the solid material region of the outer cladding (301). The outer cladding (301) has an inner wall (301a), and the cavity structure (201) has a front wall (201a) near the hollow core (101). The front wall (201a) and the inner wall (301a) of the outer cladding (301) are separated by a continuous solid material layer to form an anti-resonant layer; the cavity structure (201) is located at a corresponding position between adjacent main anti-resonant tubes (102). The outer cladding (301) is provided with at least one microchannel (401), which connects the air region defined by the cavity structure (201) and the inner wall (301a) of the outer cladding (301) and / or the outer surface of the optical fiber; the minimum lateral dimension of the microchannel (401) is smaller than the working wavelength of the optical fiber, so that the microchannel (401) forms an optical cutoff channel for the optical signal of the working wavelength, so as to suppress the leakage of the optical field along the microchannel while realizing gas communication.

[0009] Furthermore, the minimum lateral dimension of the microchannel (401) is 10nm to 500nm, preferably 50nm to 500nm; the minimum lateral dimension may also be preferably 1 / 10 to 1 / 2 of the working wavelength. The cross-section of the microchannel (401) may be slit-shaped, circular, elliptical, rhomboid, triangular, or other polygonal or irregular shapes; the microchannel (401) may extend radially and connect to the outer surface of the optical fiber to achieve adaptive air pressure balance between the cavity structure (201) and the external environment; and / or extend circumferentially and / or radially and connect to the air region defined by the inner wall (301a) of the outer cladding (301), thereby enabling gas communication between the cavity structure (201) and the hollow core (101) region.

[0010] Furthermore, the microchannel (401) used to connect the cavity structure (201) and the hollow core (101) region is preferably a single one; the microchannel (401) used to connect the cavity structure (201) and the outer surface of the optical fiber can be multiple and arranged in an array. The microchannel (401) can be disposed on the side of the cavity structure (201) away from the hollow core (101) and / or disposed at the corresponding position on the rear sidewall (201b) of the cavity structure (201). The microchannel (401) can be formed by micro-nano gaps formed during femtosecond laser processing, chemical etching, plasma etching, or fiber drawing.

[0011] Compared with the prior art, the present invention has at least the following beneficial effects:

[0012] (1) Low loss and connectivity compatibility: The microchannel (401) adopts a subwavelength lateral dimension, which forms an optical cutoff channel for the working wavelength. This can suppress the leakage of the light field along the channel while realizing the connectivity between the cavity structure (201) and the air region and / or the external environment, thereby reducing the limiting loss.

[0013] (2) Dynamic air pressure balance: The air pressure between the cavity and the outside or the hollow area is adaptively balanced through the connecting channel, which reduces the pressure difference between the inside and outside of the sealed cavity caused by temperature or ambient air pressure changes, reduces structural stress and failure risk, and is conducive to wire drawing manufacturing and long-term stable use.

[0014] (3) Sensing and environmental monitoring: The gas to be measured can be introduced into the cavity structure (201) and / or the hollow core (101) area through the micro-channel, and the long optical path advantage of the hollow core light guide can be combined to realize gas sensing, environmental monitoring and other applications.

[0015] (4) Scalable structure: The size, number, shape and arrangement of microchannels can be optimized according to different wavelengths (ultraviolet to mid-infrared) and different application requirements, and can be realized under different cavity geometries. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the cross-sectional structure of an anti-resonant hollow fiber according to an embodiment of the present invention.

[0017] Figure 2 This is a partially enlarged schematic diagram showing the connection between the cavity structure and the microchannels of the present invention.

[0018] Figure 3 This is a schematic diagram showing the trend of fiber confinement loss at a working wavelength of 1550nm when the minimum lateral dimension L of the microchannel varies from 10nm to 500nm in an embodiment of the present invention.

[0019] Figure 4 This is a schematic diagram of cavity structures with different geometric shapes in embodiments of the present invention.

[0020] Figure 5 This is a schematic diagram comparing the loss of a traditional cavity-free 4-DNANF structure at different operating wavelengths when the minimum lateral dimension L of the microchannel is 250 nm and 500 nm in an embodiment of the present invention.

[0021] Figure 6 This is a schematic diagram of different cross-sectional shapes of the microchannel (401) in an embodiment of the present invention.

[0022] Explanation of reference numerals in the attached figures

[0023] 101: Hollow core; 102: Main anti-resonant tube; 103: First-layer nested anti-resonant tube; 104: Second-layer nested anti-resonant tube; 201: Cavity structure; 201a: Front wall; 201b: Rear side wall; 301: Outer cladding; 301a: Inner wall of outer cladding; 401: Microchannel; L: Minimum lateral dimension of microchannel. Detailed Implementation

[0024] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Various modifications, alterations, or equivalent substitutions made to the embodiments of the present invention without departing from the spirit and principles thereof should fall within the scope of protection of the present invention.

[0025] Example 1: 4-DNANF anti-resonant hollow fiber with a connected cavity structure and subwavelength microchannel.

[0026] like Figure 1As shown, the optical fiber includes a hollow core 101, a plurality of main anti-resonator tubes 102 distributed around the hollow core 101, and an outer cladding 301 surrounding the main anti-resonator tubes 102. The main anti-resonator tubes 102 may contain a first layer of nested anti-resonator tubes 103 and a second layer of nested anti-resonator tubes 104. The outer cladding 301 has an inner wall 301a that defines an inner air region (including the air regions inside the hollow core 101 and the main anti-resonator tubes 102). At least one cavity structure 201 is completely embedded in the solid material region of the outer cladding 301. The cavity structure 201 is located at a corresponding position between adjacent main anti-resonator tubes 102 to suppress optical field leakage in the gap direction. The cavity structure 201 has a front wall 201a near the hollow core 101. The front wall 201a and the inner wall 301a of the outer cladding are separated by a continuous solid material layer, forming an anti-resonator layer, thereby providing an additional reflection barrier to the optical field leaking in the gap direction.

[0027] Unlike a sealed cavity, this invention provides at least one microchannel 401 within the outer cladding 301, enabling communication between the cavity structure 201 and the air region defined by the inner wall 301a of the outer cladding and / or the outer surface of the optical fiber. The minimum lateral dimension of the microchannel 401 is smaller than the operating wavelength, thus forming an optical cutoff channel for the operating wavelength optical signal. In other words, the microchannel 401 allows gas molecules to pass through, achieving pressure balance and gas introduction, but has a weak effect on the operating wavelength optical field, thereby suppressing light leakage along the channel and avoiding the introduction of significant additional losses.

[0028] Example 2: Setting the size and proportion of the microchannel.

[0029] like Figure 2 As shown, the microchannel 401 can be configured as a slit or channel connecting the cavity structure 201 with the air region or the external environment, and its minimum lateral dimension L is 10nm to 500nm, preferably 50nm to 500nm; it can also be expressed as a proportional relationship with the working wavelength λ, preferably 1 / 10 to 1 / 2 of λ. The working wavelength can cover the ultraviolet, visible, near-infrared to mid-infrared bands; the present invention uses the 1550nm band as an example for illustration, but is not limited to this band.

[0030] Example 3: Microchannel connectivity and quantity configuration.

[0031] In one embodiment, the microchannel 401 extends radially and connects to the outer surface of the optical fiber to achieve adaptive pressure balance between the cavity structure 201 and the external environment (e.g., to eliminate or reduce pressure difference during fiber drawing and use). In another embodiment, the microchannel 401 extends circumferentially and / or radially and connects to the air region defined by the inner wall 301a of the cladding, thereby enabling gas communication between the cavity structure 201 and the hollow core 101 region for gas introduction or sensing. Preferably, one microchannel 401 connects the cavity structure 201 and the hollow core 101 region between each main resonant tube to avoid introducing excessive disturbance near the hollow core region; multiple microchannels 401 connecting the cavity structure 201 and the outer surface can be arranged in an array to improve gas exchange efficiency and pressure balance speed.

[0032] Example 4: Position and shape of microchannels.

[0033] The microchannel 401 is preferably disposed on the side of the cavity structure 201 opposite to the hollow core 101 and / or at a corresponding position on the rear sidewall 201b of the cavity structure 201. The cross-sectional shape of the microchannel 401 may be slit-like. Figure 6 Examples include circles, ellipses, rhombuses, triangles, and other polygonal or irregular shapes. The slit width of the slotted channel and the minimum diameter of the circular / elliptical / polygonal hole can both be used as the minimum lateral dimension.

[0034] Example 5: Geometry of the cavity structure.

[0035] like Figure 4 As shown, the cavity structure 201 can adopt various geometric shapes to adapt to different structural parameters and process conditions, such as being circular, elliptical, racetrack-shaped, fan-shaped, crescent-shaped, polygonal, or irregular in shape. The solid material layer formed between the front wall 201a of the cavity structure 201 and the inner wall 301a of the outer cladding can have a constant thickness or a varying thickness distribution to adjust the anti-resonance suppression effect and structural strength.

[0036] Example 6: Formation process of microchannels.

[0037] The microchannel 401 can be formed by micro-nano processing in the outer cladding region using femtosecond laser processing; it can also be formed by post-processing techniques such as chemical etching and plasma etching; or it can be obtained by controlling the contact interface to form micro-nano gaps during the preform stacking and fiber drawing process. For microchannels formed by post-processing, encapsulation processes can be used at the fiber ends or in local areas to control the gas exchange area and improve reliability.

[0038] Example 7: Loss simulation verification.

[0039] like Figure 3As shown, while maintaining consistent basic structural parameters of 4-DNANF, by changing the minimum lateral dimension L of the microchannel 401 (from 10 nm to 500 nm), the confinement loss at a working wavelength of 1550 nm can be observed to change with L. Compared with the loss level of the traditional cavity-free 4-DNANF structure (~5 dB / km), it has a significant beneficial effect. Therefore, simulation results show that setting a cavity structure with subwavelength microchannel connectivity can significantly reduce confinement loss.

[0040] like Figure 5 As shown, when L is 250 nm and 500 nm, the loss curves of the structure of the present invention at different operating wavelengths exhibit a lower loss level compared to the conventional cavity-free 4-DNANF structure. This verifies that the subwavelength connectivity channel achieves connectivity without introducing unacceptable additional leakage and has a beneficial effect on reducing confinement loss. In one embodiment, compared to the structure without the microchannel 401, the additional loss introduced by the microchannel 401 is less than 15%, preferably less than 2%.

[0041] Example 8: Gas introduction and sensing applications.

[0042] In gas introduction or gas sensing applications, the gas to be measured can be introduced into the cavity structure 201 and / or the hollow core 101 region through the microchannel 401. This allows the transmitted light to interact with the gas through absorption, Raman scattering, or refractive index changes, enabling applications such as gas sensing, environmental monitoring, industrial process monitoring, or safety early warning. The connection between the microchannel 401 and the cavity structure 201 also allows for controllable gas exchange rate and response time, thereby improving sensing performance.

Claims

1. An anti-resonant hollow-core optical fiber with a connected cavity structure, characterized in that, include: Hollow core (101), located at the center of the optical fiber; Multiple main anti-resonant tubes (102) are distributed around the hollow core (101). An outer cladding layer (301) surrounds the main anti-resonant tube (102), and the outer cladding layer (301) has an inner wall (301a). At least one cavity structure (201) is fully embedded in the solid material region of the outer cladding (301), the cavity structure (201) having a front wall (201a) near the hollow core (101), the front wall (201a) being separated from the inner wall (301a) of the outer cladding (301) by a continuous solid material layer to form an anti-resonance layer, the cavity structure (201) being located at a corresponding position between adjacent main anti-resonance tubes (102); The outer cladding layer (301) is provided with at least one microchannel (401). The microchannel (401) connects the air region defined by the cavity structure (201) and the inner wall (301a) of the outer cladding (301) and / or the outer surface of the optical fiber.

2. The anti-resonant hollow-core optical fiber according to claim 1, characterized in that, The minimum lateral dimension of the microchannel (401) is 10 nm to 500 nm; preferably 50 nm to 500 nm.

3. The anti-resonant hollow-core optical fiber according to claim 1 or 2, characterized in that, The minimum lateral dimension of the microchannel (401) is 1 / 10 to 1 / 2 of the operating wavelength.

4. The anti-resonant hollow-core optical fiber according to any one of claims 1 to 3, characterized in that, The cross-section of the microchannel (401) is slit-shaped, and the slit width is the minimum lateral dimension.

5. The anti-resonant hollow-core optical fiber according to any one of claims 1 to 3, characterized in that, The cross-section of the microchannel (401) is a circle, ellipse, rhombus, triangle or other polygon or irregular shape, and its minimum diameter is the minimum lateral dimension.

6. The anti-resonant hollow-core optical fiber according to any one of claims 1 to 5, characterized in that, The microchannel (401) extends radially and connects to the outer surface of the optical fiber to achieve an adaptive balance of air pressure between the cavity structure (201) and the external environment.

7. The anti-resonant hollow-core optical fiber according to any one of claims 1 to 5, characterized in that, The microchannel (401) extends circumferentially and / or radially and connects to the air region defined by the inner wall (301a) of the outer cladding (301), thereby enabling gas communication between the cavity structure (201) and the hollow core (101) region.

8. The anti-resonant hollow-core optical fiber according to any one of claims 1 to 7, characterized in that, The microchannel (401) is disposed on the side of the cavity structure (201) away from the hollow core (101) and / or disposed at the corresponding position on the rear sidewall (201b) of the cavity structure (201).

9. The anti-resonant hollow-core optical fiber according to any one of claims 1 to 8, characterized in that, The microchannel (401) is formed by one or a combination of the following methods: femtosecond laser processing, chemical etching, plasma etching, or micro-nano gaps formed during wire drawing.

10. The anti-resonant hollow-core optical fiber according to any one of claims 1 to 9, characterized in that, Compared to a structure without the microchannel (401), the additional loss introduced by the microchannel (401) is less than 15%; preferably less than 2%.

11. The application of the anti-resonant hollow optical fiber according to any one of claims 1 to 10 in gas introduction or gas sensing, characterized in that, The gas to be tested is introduced into the cavity structure (201) and / or the hollow core (101) region through the microchannel (401), and gas sensing is achieved by the interaction between the transmitted light of the anti-resonant hollow core optical fiber and the gas to be tested.

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