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

Vincetti, Luca; Setti, Valerio

doi:10.1364/oe.20.014350

Cited by 68 publications

(43 citation statements)

References 27 publications

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“…Numerous metal- and dielectric-based waveguides234567891011121314151617181920212223242526272829303132333435363738394041424344 and devices, such as fiber Bragg gratings (FBGs)454647 and couplers4849505152535455, have been studied. However, restistive losses of metals and in particular high absorption of most dielectric materials make design of low loss THz waveguides and devices challenging.…”

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confidence: 99%

“…Several designs for dielectric waveguides with THz radiation propagation in air have already been reported, including sub-wavelength fibers2122, porous fibers23242526, and hollow-core waveguides272829303132333435363738394041424344. The guiding mechanism in sub-wavelength fibers is based on total internal reflection.…”

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confidence: 99%

“…Hollow-core waveguides, which normally consist of an air-core and a structured cladding, can alleviate external disturbances as most of the field is guided within the air core region. Several designs based on this kind of structure have been proposed, such as photonic band gap (PBG) type fibers2829303132, Kagome type fibers333435 and metal/dielectric tubes3637383940414243. For PBG type fibers, the mode is confined within the air core with the help of dielectric reflectors or band-gap reflectors, which prohibit the field from extending into the plane of the PBG reflectors.…”

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confidence: 99%

“…Porous-core honeycomb PBG fibers3132 can to some extent alleviate such problems of air core fibers, at the expense of introducing more material loss. For Kagome-type fibers333435, the cladding can be seen as composed of an array of hollow tubes with different shapes. Unlike the PBG type fibers that guide light by means of a photonic band gap in the cladding, guiding in Kagome-type fibers is based on the inhibited coupling due to the low density of cladding modes and small spatial overlap of cladding modes with core modes.…”

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confidence: 99%

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Dielectric tube waveguides with absorptive cladding for broadband, low-dispersion and low loss THz guiding

Bao

Nielsen

Bang

et al. 2015

Sci Rep

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Research on terahertz waveguides is experiencing a tremendous growth due to their importance for compact and robust THz systems. However, designing compact, broadband, mechanically stable and environmentally shielded THz waveguides is still a challenge due to high losses of both metals and dielectrics in this frequency range. Here we report on a novel twist on the classical tube waveguide where we deliberately introduce a thick and highly lossy cladding layer. By this we attenuate the field in the cladding and thus prevent interference with the core field. This mechanism breaks the well-known ARROW guiding mechanism, and as a result, extremely broad bandwidth and low dispersion can be achieved with a very simple design. Since the main part of the field propagates inside the air-core, the propagation loss is still kept at a very low level. Simulations, analytical modelling and experiments verify our findings. The proposed THz waveguide is robust, insensitive to external perturbation and easy to handle, and thus the design represents a significant advance of the field of THz dielectric waveguides suitable for the 0.3–1 THz band which in the future will be important for ultrafast wireless communication systems.

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Dielectric tube waveguides with absorptive cladding for broadband, low-dispersion and low loss THz guiding

Bao

Nielsen

Bang

et al. 2015

Sci Rep

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“…It was proven that optical properties of the KF largely depend on the first air cladding layer surrounding the air core 18 . Subsequently, a simplified antiresonant structure with one air cladding layer has been widely investigated as a hollow core antiresonant fiber 19, 20 or an inhibited coupling fiber 21 where the inhibited coupling model offers more precise description of the fiber guidance 15, 16 . The simplified structure features a negative core curvature, a non-touching core boundary and one tube cladding layer 16, 19, 22, 23 , thus often being named as Tube Lattice Fiber (TLF) 24–26 .…”

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Function of second cladding layer in hollow core tube lattice fibers

Huang

Yoo

Yong

2017

Sci Rep

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Modes attenuation of the tube lattice fiber (TLF) is characterized by D/λ, where D is the core diameter and λ is the wavelength. Hence, the TLF is structured with a large core to ensure a low attenuation loss. A small core, on the other hand, facilitates the gas-filled TLF applications, but at the expense of the increased mode attenuation. We show that adding a second cladding layer to the conventional one layer TLF (1TLF) can resolve the contradicting requirements. The mode attenuation of TLF with two cladding layers (2TLF) is less influenced by the D/λ value as compared to 1TLF, thus realizing a low loss small core TLF. Furthermore, we found that adding the second layer brings another advantage to a bending performance. With a determined core size, D, a 1TLF with smaller capillary hole size, d, experiences less bending loss. However, the reduced d increases the confinement loss that counteracts the bending loss improvement. This confliction is substantially alleviated in 2TLF thanks to the second cladding layer. Theoretical investigations and experimental demonstrations are presented to evidence the important role of the second cladding ring in the TLF, which has been overlooked in prior studies.

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Conquering the Rayleigh Scattering Limit of Silica Glass Fiber at Visible Wavelengths with a Hollow‐Core Fiber Approach

Gao

Ding

Hong

2019

Laser & Photonics Reviews

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The ultimate limit on fiber loss is set by the intrinsic Rayleigh scattering of silica glass material. Here, we challenge this limit in the visible region by using a hollow-core fiber approach. Two visible-guiding hollow-core conjoined-tube negativecurvature fibers are successfully fabricated and exhibit the overall losses of 3.8 dB/km at 680 nm and 4.9 dB/km at 558 nm respectively. The loss of the latter fiber surpasses the Rayleigh scattering limit of silica glass fiber in the green spectral region by 2 dB. Numerical simulation indicates that this loss level is still much higher than the fundamental surface scattering loss limit of hollow-core fiber.After over 40 years of technological refinement, the Rayleigh scattering loss (RSL), caused by microscopic density fluctuation frozen in bulk glass [1], has become the dominant loss constituent in state-of-the-art silica glass fiber (SGF) throughout most of its operating wavelength. The fact that the RSL is fundamentally insurmountable casts a shadow on future applications of optical fiber ranging from communications to sensing and laser. First, the most efficient light transmission window in a fiber is restricted near 1.55 μm wavelength with the minimum loss of ~ 0.14 dB/km [2] and the bandwidth of some tens of THz [3]. In order to send signals through long distance in a fiber, the carrier wavelength of light usually has to be converted to the telecom band [4], introducing great complexity in the design of long-haul optical fiber systems. Second, the λ −4 wavelength dependence of the RSL is against the trend of employing advanced fiber laser technology in versatile areas, for instance, biochemical imaging and materials-processing, toward shorter and shorter wavelengths for better resolution [5,6].Utilizing fluoride glass or multi-component oxide glass, which is characterized by lower glass transition temperature and thus lower density fluctuation, is expected to reduce the RSL by one order of magnitude, e.g., ~ 0.01 dB/km RSL in fluoride glass at 2.5 µm [7] and ~ 0.05 dB/km RSL in sodium silicate glass at 1.55 μm [8]. However, in realistic fiber drawing, significantly high extrinsic losses from impurity, crystallization, defect, etc, have not yet been overcome [7], leaving these soft glass fibers inferior to SGF in terms of propagation attenuation.Since their first demonstration [9], the possibility that hollow-core photonic bandgap fibers (HC-PBGFs) can bypass the RSL limit of SGF has been highlighted and eagerly anticipated. HC-PBGF fills its core with dry air whose RSL is more than 200 times lower than in silica glass [10].

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

Cited by 68 publications

References 27 publications

Dielectric tube waveguides with absorptive cladding for broadband, low-dispersion and low loss THz guiding

Dielectric tube waveguides with absorptive cladding for broadband, low-dispersion and low loss THz guiding

Function of second cladding layer in hollow core tube lattice fibers

Conquering the Rayleigh Scattering Limit of Silica Glass Fiber at Visible Wavelengths with a Hollow‐Core Fiber Approach

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