Hollow-core Anti-resonant Fiber Research Articles

Truncated Anti-Resonant Hollow-Core Fiber for Reduced Microstructure Diameter

Truncated Anti-Resonant Hollow-Core Fiber for Reduced Microstructure Diameter

A Hollow-core Anti-resonant Fiber Multi-Objective Multi-Modal Optimization Assisted by a Proxy Model Combined with Clustering Algorithm

A Hollow-core Anti-resonant Fiber Multi-Objective Multi-Modal Optimization Assisted by a Proxy Model Combined with Clustering Algorithm

High-efficiency distortion-free delivery of 3 kW continuous-wave laser using low-loss multi-mode nested hollow-core anti-resonant fiber

High-efficiency distortion-free delivery of 3 kW continuous-wave laser using low-loss multi-mode nested hollow-core anti-resonant fiber

Random Design Variations of Hollow-core Anti-resonant Fibers: A Monte-Carlo Study

Random Design Variations of Hollow-core Anti-resonant Fibers: A Monte-Carlo Study

Multi-layered cladding based ultra-low loss, single mode antiresonant hollow core fibers

In reality, an efficient platform for high-power laser delivery is highly important, which can be justified by readily available fiber lasers, and hollow-core fiber can be the best platform for guiding high optical power over long distances. The constraints include designing new cladding geometry, which may lead to a higher laser induced damage threshold in the fiber’s structure, having low losses along with a single mode nature. This article reports a new antiresonant fiber that has a hollow core and a triple-layered cladding configuration with only circular tube elements. The effects of multiple layers corresponding to the number of tube rings in the cladding geometry are well explored, which leads to understanding the physical insight of inter-layers. In comparison to double-layered cladding elements fiber, the proposed fiber significantly reduces loss by an order of two and reveals a minimum leakage loss of 5.82 × 10−5 dB/km at the chosen wavelength of 1.06 µm through the proper arrangement of cladding elements. We achieved a maximal higher order mode extinction ratio of about 104 (indicates the excellent single mode properties) and comparatively a little bending-induced loss of 9.00 × 10−4 dB/km, when the radius of bending is 14 cm. As a result, our studies on new multilayer fiber designs are not only useful for delivering high laser power but also serve as guidelines for the experimental realization of future multilayered cladding fibers.

Hollow-core anti-resonant fiber magnetic field sensor based on negative curvature Semi-Tubular

Magnetic field detection is critical for geological exploration in complex environments. Based on the principle of leaky mode resonance (LMR), a semi-tubular hollow-core anti-resonant fiber (HC-ARF) filled with a magnetic fluid (MF) is proposed for magnetic field sensing in this study. When the semi-tubular air cladding cavity is filled with MF, a Fabry–Perot (F-P) resonator can be formed between the MF and the silica cladding, and the negative-curvature semi-tubular structure can confine the light in the fiber core. Different magnetic field strengths vary the reflectivity and resonance conditions of the F-P resonator, which in turn affect the resonance wavelength and transmittance. The results show that the sensitivity of the wavelength shift can reach 68.39 pm/Oe for magnetic field strengths in the range of 60–180 Oe. This HC-ARF magnetic field sensor can realize magnetic field detection under light sources of different wavelengths according to the selection of the resonance order. The sensor exhibits a low loss, wide bandwidth, and high sensitivity, and thus it has good development prospects for geological exploration.

Modified genetic algorithm for inverse design of anti-resonant hollow core fiber with low confinement loss

Low-loss anti-resonant hollow core fibers (AR-HCF) are important for optical communication systems, photonics-enabled sensors, and exploring nonlinear dynamics with gas-light interaction. However, the design of AR-HCF that facilitates optical pulse propagation with desirable properties remains highly intricate and time-consuming. In this work, a modified genetic algorithm (MGA) with a small dataset is presented to reduce the confinement loss (CL) of AR-HCF at the telecom wavelength. The algorithm has been modified through a non-uniform mutation process and a simulated binary crossover method to enhance its searching capability and ensure a stable convergence. The inverse design method for AR-HCF, which combines the algorithm with a full vector finite-element method based on a modal solver, can be implemented to search for approximately optimal designs. In our study, MGA is utilized to optimize the tube diameter and thickness of single-ring tubular AR-HCF and nested anti-resonant nodeless fiber (NANF) at 1550 nm. As a result, optimized ratios of 25.4% and 79.8% are achieved for a core diameter of 40 µm, respectively. In addition, MGA also provides the corresponding optimal range of fiber parameters, which is helpful for actual fabrication.

Highly sensitive temperature sensor using nested hollow-core anti-resonant fibers

A highly sensitive temperature sensor based on composite nested negative curvature hollow-core fiber is proposed. Three resonant tubes are nested inside the cladding tubes to induce a resonant coupling between the fundamental core mode and the dielectric mode of the nested resonant tube. Three glass-sheet conjoined nested tubes are introduced to suppress the comparatively low loss higher-order mode LP02. All the air-holes are filled with temperature-sensitive liquid of ethanol. As the temperature changes, the resonant dip in the transmission spectrum corresponding to the coupling will shift. Numerical simulation results indicate that the temperature sensitivity is 3.36 nm °C−1 in the range of 20 °C–40 °C. Since there is no need of any special post-processing, such as selective infiltration or material coating for the sensors proposed, the sensor provides a promising mechanism for the optical fiber temperature sensing.

A Highly Sensitive Curvature and Rotation Angle Sensor Based on Asymmetric Hollow-Core Anti-Resonant Fiber

A Highly Sensitive Curvature and Rotation Angle Sensor Based on Asymmetric Hollow-Core Anti-Resonant Fiber

Wavelength modulation spectroscopy of oxygen inside anti-resonant hollow-core fiber-based gas cell

Optical detection of oxygen in A-band (near 13140 cm−1 or 761 nm) with tunable laser diode spectroscopy has been investigated and demonstrated in the past. However, as the demand for miniaturization of gas sensors increases, the hollow-core optical fibers emerge as a promising alternative to conventional large-volume gas absorption cells. In this paper we present a highly convenient, robust and scalable all-fiber setup that utilizes a 1.2 m silica anti-resonant hollow-core fiber as a small-footprint gas cell. Using tunable laser diode, the absorption spectra of oxygen in range from 13133.44 to 13148.12 cm−1 have been recorded. We also performed wavelength modulation spectroscopy of oxygen for samples with various oxygen concentrations and achieved a detection limit of approximately 170 ppm for an averaging time of 5 s. Furthermore, the versatility of the sensing approach is demonstrated by showing its ability to simultaneously detect oxygen at 761 nm and methane at 1651 nm inside the same hollow-core fiber.

Single-polarization single-mode broadband ultra-low loss hollow-core anti-resonant fiber with nested double C-type cladding tubes

A novel five-tube nested double C-type single-polarization hollow-core anti-resonant fiber (HC-ARF) is proposed for single-polarization single-mode, ultra-low loss, and broadband characteristics. Different tube thicknesses are introduced along the orthogonal direction to couple the x-polarized fundamental mode (FM) to the silica modes (SMs). At the same time, the y-polarized FM is tightly bound in the core, achieving a high polarization extinction ratio (PER). In order to achieve large bandwidth, a layer of high-refractive-index silicon material is coated on the inner surface of the cladding tube. To the best of our knowledge, the proposed single-polarization HC-ARF has the highest PER at 1.55μm with a remarkable value of 162486 so far, while the y-polarized FM loss is only 1.4 × 10-3 dB/km. However, the single-polarization bandwidth remains limited. By optimizing the structural parameters on single-polarization bandwidth, the HC-ARF at 1.55μm for single-polarization single-mode transmission is obtained with a high-order mode extinction ratio (HOMER) and PER of 2891, 9531, respectively. In addition, a remarkably high single-polarization bandwidth of up to 150 nm is achieved with ultra-low confinement loss (CL) as low as 2.8 × 10-3 dB/km. Furthermore, the proposed fiber exhibits good bending characteristics, with a bending loss of 6.7 dB/km at the bending radius of 5 cm in the x-direction.

A Novel Optical Fiber Terahertz Biosensor Based on Anti-Resonance for The Rapid and Nondestructive Detection of Tumor Cells.

The sensitive and accurate detection of tumor cells is essential for successful cancer therapy and improving cancer survival rates. However, current tumor cell detection technologies have some limitations for clinical applications due to their complexity, low specificity, and high cost. Herein, we describe the design of a terahertz anti-resonance hollow core fiber (THz AR-HCF) biosensor that can be used for tumor cell detection. Through simulation and experimental comparisons, the low-loss property of the THz AR-HCF was verified, and the most suitable fiber out of multiple THz AR-HCFs was selected for biosensing applications. By measuring different cell numbers and different types of tumor cells, a good linear relationship between THz transmittance and the numbers of cells between 10 and 106 was found. Meanwhile, different types of tumor cells can be distinguished by comparing THz transmission spectra, indicating that the biosensor has high sensitivity and specificity for tumor cell detection. The biosensor only required a small amount of sample (as low as 100 μL), and it enables label-free and nondestructive quantitative detection. Our flow cytometry results showed that the cell viability was as high as 98.5 ± 0.26% after the whole assay process, and there was no statistically significant difference compared with the negative control. This study demonstrates that the proposed THz AR-HCF biosensor has great potential for the highly sensitive, label-free, and nondestructive detection of circulating tumor cells in clinical samples.

Enhancing single-mode guidance using avoided crossings in anti-resonant hollow-core fibers with five nested cladding tubes

We numerically analyze the nested anti-resonant nodeless fibers (NANFs) with five tubes to determine the best single-mode guidance and low confinement loss for the fundamental mode simultaneously. We derive the empirical relation between structural parameters that lead to avoided crossings between the core higher order modes (HOMs) and the cladding tube modes in a 5-tube nested design to achieve robust single-mode guidance. We report a low confinement loss of 1.17×10−3 dB/km and 0.23 dB/km, and huge HOM extinction ratio (HOMER) of the order of 105 and 104 at wavelengths of 650 nm and at 1550 nm respectively. We also investigate the fabrication tolerances of the confinement loss and HOMER to the changes in design parameters. These 5-tube NANFs exhibit a broad loss spectrum of 200 nm with loss of fundamental mode ¡ 0.003 dB/km and HOMER of 16000 centered around 650 nm. NANFs find applications in quantum communications, sensing and telecommunications and this work can be helpful in design optimization of such fibers.

Non-destructive characterization of nested and double nested antiresonant nodeless fiber microstructure geometry.

Antiresonant hollow-core fibers (HCFs) are rapidly establishing themselves as a promising technology with the potential to overcome the limitations faced by conventional solid-core silica fibers. The optical properties and performance of these fibers depend critically on the precise control and uniformity of their delicate glass microstructure at all points along the length of the fiber. Their fabrication is complicated by the inability to monitor this microstructure without cutting into the fiber and viewing a sample under a microscope during the fiber draw. Here we show that a non-destructive interferometric technique using side-illumination of the fiber and first demonstrated for simple tubular fibers can be used to measure the diameters of all nested capillary elements of two promising HCF designs: the nested and double-nested antiresonant nodeless fiber (NANF and DNANF, respectively) with accuracy comparable to a microscope measurement. We analyze the complexities enabled by the presence of multiple nested capillaries in the structure and present techniques to overcome them. These measurements, carried out on a small (∼50 cm) length of fiber, require less than 60s to collect and process the data for all capillaries. We also show how we can use this technique to detect defects in the fiber, making it a potential candidate for real-time in-situ monitoring of NANF and DNANF structures during fabrication.

Highly Birefringent Anti-Resonant Hollow-Core Fiber With a Low Loss

Highly Birefringent Anti-Resonant Hollow-Core Fiber With a Low Loss

Ultrahigh Sensitivity Refractive Index Sensor Based on Surface Plasmon Resonance Effect of Double-Ring Hollow-Core Anti-Resonant Fiber

Ultrahigh Sensitivity Refractive Index Sensor Based on Surface Plasmon Resonance Effect of Double-Ring Hollow-Core Anti-Resonant Fiber

Interconnectivity between effectively single-moded antiresonant hollow core fibres and conventional single-mode fibres

We review the topic, focusing first on a discussion of the key parameters, limits of coupling loss, and measurement techniques. We then follow by reviewing the literature, including mode-field adaptation methods, and assembly approaches. Finally, we briefly cover the topic of hollow core fibre connection with non-standard single mode fibres, and finish with a review of components that can be made directly within the connection. We conclude with a summary of key achievements and present our view on key remaining challenges.

Sensitive carbon monoxide detection based on light induced thermoelastic spectroscopy with a hollow waveguide and 2.3 μm diode laser

In this paper, a sensitive carbon monoxide (CO) detection system based on light induced thermoelastic spectroscopy (LITES) using a hollow waveguide (HWG) and 2.3 μm diode laser is reported. The HWG has an inner diameter of 4 mm, in which light and CO gas can fully react. Its large inner diameter makes optical coupling easier compared to hollow-core anti-resonant fiber (HC-ARF). In addition, it has the advantages of wide transmission band range, simple structure and low loss. An absorption line of CO located at 4288.26 cm−1 was chosen, therefore a diode laser with an emission wavelength of 2.3 μm was selected as the excitation source. In the experiment, the current modulation depth of the CO-HWG-LITES sensor was optimized to 34.6 mA. The results demonstrated a very nice linear relationship between the CO concentration and the corresponding 2f signal peak value, indicating that the CO-HWG-LITES sensor had a superior linear response to the gas concentration. The minimum detection limit (MDL) for CO in this system was determined to be 31.6 ppm. Finally, the Allan deviation analysis was performed and results indicated that the MDL can reach 4.7 ppm when the integration time was 100 s.

Antiresonant hollow-core fiber Bragg grating design.

Fiber Bragg gratings (FBGs) inscribed in hollow-core fibers hold a potential to revolutionize the field of gas photonics by enhancing the performance and versatility of hollow-core fiber-based matter cells. By effectively transforming these cells into cavities, FBGs can significantly extend the effective length of light-matter interactions. Traditional FBG inscription methods cannot be extended to hollow-core fibers, because light in the fundamental mode is predominantly confined to the hollow region where an index change cannot be induced. In this Letter, we propose a bi-thickness dual-ring hollow-core antiresonant fiber (DRHCF) design that achieves substantial overlap between the fundamental mode and cladding glass in a well-controlled manner, ensuring a strong FBG response with a minimal insertion loss. Through detailed numerical investigations, we demonstrate the feasibility of creating a high reflection FBG in the DRHCF using standard FBG inscription techniques. The proposed device is expected to have a length of <1 cm and the insertion loss of <0.3 dB, including splice loss.

2.2 kW single-mode narrow-linewidth laser delivery through a hollow-core fiber

Antiresonant hollow-core fibers (AR-HCFs) have opened up exciting possibilities for high-energy and high-power laser delivery because of their exceptionally low nonlinearities and high damage thresholds. While these fiber designs offer great potential for handling kilowatt-class powers, it is crucial to investigate their performance at multi-kW power levels. Until now, transmission of narrow-linewidth single-mode lasers at multi-kW power levels through a HCF has not been demonstrated, to our knowledge. Here, we present the delivery of a record 2.2 kW laser power with an input spectral linewidth of 86 GHz, centered at 1080 nm, while maintaining 95% transmission efficiency and beam quality (M2) of 1.03. This was achieved via a 104.5 m single-mode five-tube nested AR-HCF with 0.79 dB/km loss. Furthermore, we show power delivery of 1.7 kW with a spectral linewidth as narrow as 38 GHz through the same fiber. Our results could lead to a new generation of fiber-based laser beam delivery systems with applications in precision machining, nonlinear science, directed energy, and power beaming over fiber.