Inhibited-coupling Fiber Research Articles

Azimuthal Fourier decomposition for loss analysis of hollow-core tube lattice fibers, Part II: Tube thickness variation effects

The effect on confinement loss of thickness variations along the perimeter of the tubes composing the cladding of inhibited-coupling guiding Tube Lattice hollow-core fibers is investigated by using the Azimuthal Fourier Decomposition technique (developed in Part I) for the description of the cladding modal dynamics and their interaction with the fundamental core mode. The results show that the thickness inhomogeneity affects the confinement loss spectrum through confinement loss increase and frequency red- and blue-shift of the high-loss spectral regions. The magnitudes of the confinement loss increase and the high-loss region frequency shift strongly depend on the spatial distribution of the thickness inhomogeneity. The study provides insight into the loss mechanism of non-ideal tube lattice fibers, it allows to quantify the impact of such kind of structural deformations, identifying the route to make fibers more resilient to such fabrication imperfections, and highlighting once again the importance played in inhibited-coupling fibers by the interaction between core modes and the intricate set of cladding modes.

Analytical Formulas for Dispersion and Effective Area in Hollow-Core Tube Lattice Fibers

In this work, we propose analytical formulas for the estimation of dispersion properties and effective area of the fundamental mode of hollow-core inhibited coupling fibers with a microstructured cladding composed by a ring of dielectric tubes. The formulas are based on a model which has already been successfully applied to the estimation of confinement loss. The model takes into account the effects of the coupling of the fundamental core mode with the cladding modes in the context of the single-tube approximation. Effective index, group velocity dispersion, and effective area of the fundamental mode are estimated and compared with the results obtained from numerical simulations, by considering ten different fibers. The comparison shows a good accuracy of the proposed formulas, which do not require any tuning of fitting parameters. On the basis of the analysis carried out, a scaling law relating the effective area to the core radius is also given. Finally, the formulas give a good estimation of the same parameters of other Hollow-core inhibited coupling fibers, such as nested, ice-cream, and kagome fibers.

Hollow Core Inhibited Coupled Antiresonant Terahertz Fiber: A Numerical and Experimental Study

In this article, a hollow core antiresonant photonic crystal fiber is analyzed for terahertz applications. A numerical analysis of the proposed fiber is first carried out to minimize coupling between the core and cladding modes. The modeling of the scaled-up and inhibited coupling fiber is carried out by means of a finite element method, which is then demonstrated using a Zeonex filament fiber, fabricated by fused deposition modeling of 3-D printing technology. The simulation is carried out to analyze both the transmission and possibility of refractometric sensing, whereas the experimental analysis is carried out using terahertz time-domain spectroscopy, and supports our numerical findings, illustrating how the proposed fibers can be used for low-loss transmission of terahertz waves. The simplicity of the proposed fiber structures facilitates fabrication for a number of different transmission and sensing applications in the terahertz range.

Fusion splice between tapered inhibited coupling hypocycloid-core Kagome fiber and SMF.

We report for the first time on tapering inhibited coupling (IC) hypocycloid-core shape Kagome hollow-core photonic crystal fibers whilst maintaining their delicate core-contour negative curvature with a down-ratio as large as 2.4. The transmission loss of down-tapered sections reaches a figure as low as 0.07 dB at 1550 nm. The tapered IC fibers are also spliced to standard SMF with a total insertion loss of 0.48 dB. These results show that all-fiber photonic microcells with the ultra-low loss hypocycloid core-contour Kagome fibers is now possible.

Ultra-Large Core Size Hypocycloid-Shape Inhibited Coupling Kagome Fibers for High-Energy Laser Beam Handling

We report on the fabrication and characterization of 19-cell hypocycloid-shape Kagome fibers with core size larger than 100 μm. These inhibited coupling fibers present low propagation loss (100 dB/km) over broad transmission range with low chromatic dispersion combined with ultra-low power overlap with silica surround, making them an efficient solution for ultra-high power laser handling, ultra-fast laser delivery, and plasma photonics applications.

Design of the low-loss wide bandwidth hollow-core terahertz inhibited coupling fibers

A multi-perspective numerical analysis of propagation loss in inhibited coupling fibers (ICFs) in terahertz (THz) band is presented. It is shown that the core boundary strut shape is a critical factor affecting the confinement loss. The simulation results demonstrate that the closer to a circular arc the struts, the lower the confinement loss. Furthermore, the strut thickness and the material refractive index determine the frequencies and the bandwidths of the low loss region. With the decrease of the strut thickness and material refractive index, the low loss region will be shifted toward the higher frequency, and the widths of low loss regions will be broadened. Besides, when material absorption is considered in simulation, the ICFs averaged propagation loss is still about three orders of magnitude lower than the material absorption loss itself. The conclusions could give valuable guidance for the design and fabrication of THz ICFs.

Extra loss due to Fano resonances in inhibited coupling fibers based on a lattice of tubes

Confinement loss of inhibited coupling fibers with a cladding composed of a lattice of tubes of various shapes is theoretically and numerically investigated. Both solid core and hollow core are taken into account. It is shown that in case of polygonal shaped tubes, confinement loss is affected by extra loss due to Fano resonances between core modes and cladding modes with high spatial dependence. This explains why hollow core Kagome fibers exhibit much higher confinement loss with respect to tube lattice fibers and why hypocycloid core cladding interfaces significantly reduce fiber loss. Moreover it is shown that tube deformations, due for example to fabrication process, affect fiber performances. A relationship between the number of polygon sides and the spectral position of the extra loss is found. This suggests general guide lines for the design and fabrication of fibers free of Fano resonance in the spectral range of interest.