Picometer-scale surface roughness measurements inside hollow glass fibres

Brun, C.; Buet, Xavier; Bresson, Bruno; Capelle, M. S.; Ciccotti, Matteo; Ghomari, Achwak; Lecomte, P.; Roger, J.P.; Petrovich, M. N.; Poletti, F.; Richardson, David J.; Vandembroucq, Damien; Tessier, Gilles

doi:10.1364/oe.22.029554

Cited by 14 publications

(10 citation statements)

References 15 publications

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“…The quantitative characterization of the roughness spectrum of glass interfaces has recently been the subject of a growing interest in the context of the development of Hollow-Core Photonic Band-Gap Fibres (HC-PBGF) [14][15][16][17]. In such microstructured fibres, light propagates through air within the hollow core and the ultimate losses are expected to be determined by the scattering from the inner interfaces of the fibre [18].…”

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confidence: 99%

Anisotropic Superattenuation of Capillary Waves on Driven Glass Interfaces

et al. 2017

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Metrological AFM measurements are performed on the silica glass interfaces of photonic band-gap fibres and hollow capillaries. The freezing of attenuated out-of-equilibrium capillary waves during the drawing process is shown to result in a reduced surface roughness. The roughness attenuation with respect to the expected thermodynamical limit is determined to vary with the drawing stress following a power law. A striking anisotropic character of the height correlation is observed: glass surfaces thus retain a structural record of the direction of the flow to which the liquid was submitted.What governs the structure of a glass surface? To very good approximation, the bulk structure of a vitreous material resembles a snapshot of the liquid before glass transition [1]. Similarly, the surface of a glass corresponds to the frozen liquid interface [2], and can reveal frozen surface modes of this interface. Over a wide range of length scales, from the nanometer up to the millimeter range, the sub-nanometer roughness of a fire-polished glass surface results from the superposition of frozen thermal equilibrium capillary waves of the liquid [3].At equilibrium, capillary fluctuations of liquid interfaces originate from the interplay between thermal noise (k B T ) and interface tension (γ), and result in a superposition of capillary waves. Height fluctuations scale as:which equals 0.3-0.4 nm for most simple liquids. Liquid interfaces are thus extremely smooth. Thermal interface fluctuations correspond to a lower bound of the interface width imposed by equilibrium thermodynamics. In this context, the application of any external field is usually expected to enhance the level of fluctuations. In the presence of a flow, amplification of capillary fluctuations typically gives rise to hydrodynamic instabilities [4]. However recent results suggest that shear flow may in fact induce a non-linear attenuation of capillary waves [5][6][7].Here we present an accurate experimental characterization of such an attenuation of capillary fluctuations on glass surfaces. In particular, we show that a glass surface retains a structural record of the direction of the flow to which the liquid was submitted. Performing high precision Atomic Force Microscopy (AFM) roughness measurements on the inner glass interfaces of photonic band-gap fibres and hollow capillaries produced by fibre drawing, we show that driven glass interfaces re-FIG. 1. Sketch of the drawing of Hollow Core Photonic Band Gap Fibres (PBGF).The two AFM measurements represent the surface topography of the inner surfaces of a PBGF before (preform) and after (fibre) the hot drawing region (in orange). While isotropic before drawing, the sub-nanometer roughness exhibits clear elongated patterns along the fibre axis after drawing. The color bar represents a height range of 1.6 nm.sult from the freezing of attenuated capillary waves. The roughness is strongly anisotropic with an overall amplitude that presents a non-linear attenuation with respect to the expected equilibrium thermodynamic...

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confidence: 99%

Anisotropic Superattenuation of Capillary Waves on Driven Glass Interfaces

et al. 2017

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“…To assess the quality of the core surfaces in the fiber, optical profilometry and atomic force microscopy (AFM) have been employed. Figure 1b shows typical height profiles (Δ h ) along the fiber axis measured by using AFM (top plot) and a picometer-sensitivity optical profilometer (bottom plot) 22 , 23 . Figure 1c , in turn, presents a representative AFM-measured surface profile taken for a 6 μm × 6 μm area on the fiber core surface.…”

Section: Resultsmentioning

confidence: 99%

Hollow-core fibers with reduced surface roughness and ultralow loss in the short-wavelength range

et al. 2023

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While optical fibers display excellent performances in the infrared, visible and ultraviolet ranges remain poorly addressed by them. Obtaining better fibers for the short-wavelength range has been restricted, in all fiber optics, by scattering processes. In hollow-core fibers, the scattering loss arises from the core roughness and represents the limiting factor for loss reduction regardless of the cladding confinement power. Here, we report on the reduction of the core surface roughness of hollow-core fibers by modifying their fabrication technique. The effect of the modified process has been quantified and the results showed a root-mean-square surface roughness reduction from 0.40 to 0.15 nm. The improvement in the core surface entailed fibers with ultralow loss at short wavelengths. The results reveal this approach as a promising path for the development of hollow-core fibers with loss that can potentially be orders of magnitude lower than the ones achievable with silica-core counterparts.

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“…However, the functional principle of a GRS requires a surface map representing the actual surface topography to compensate for path length effects. Another differential picometer profiliometry approach is described in [8], where the use of a Wollaston prism allows beams to scan in very close proximity due to the polarization routing.…”

Section: Introductionmentioning

confidence: 99%

Differential common path interferometry for picometre surface metrology

Schulte¹,

Sell²,

Koegel³

et al. 2021

International Conference on Space Optics — ICSO 2020

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Future space based missions for gravitational wave research call for an improved inertial reference sensor with acceleration noise levels of fm/s 2 . Spherical test masses can enable increased performance by suspension-free operation, contrary to cuboid solutions suffering from cross-coupling of attitude control noise. However, interferometric readout is affected by surface irregularities and test mass tumbling [1]. An accurate surface map for compensation must be established for compensation, either by characterisation a priori or in flight, when optical path length changes due to surface occur in the measurement band. We demonstrate a method for generating a surface map of a spherical body with optical point sensors using a differential method to suppress common mode errors present, taking advantage of the excellent performance of heterodyne interferometry at sub-nanometer levels. A measurement setup is proposed in which two beams of a Nd:YAG Michelson interferometer are used to scan the surface, which is afterwards reconstructed from the differential measurement. Such a method could potentially benefit other research areas, such as the precise determinations of the Avogadro constant [2] or aspheric surface metrology.

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Picometer-scale surface roughness measurements inside hollow glass fibres

Cited by 14 publications

References 15 publications

Anisotropic Superattenuation of Capillary Waves on Driven Glass Interfaces

Anisotropic Superattenuation of Capillary Waves on Driven Glass Interfaces

Hollow-core fibers with reduced surface roughness and ultralow loss in the short-wavelength range

Differential common path interferometry for picometre surface metrology

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