Long-range optical trapping and binding of microparticles in hollow-core photonic crystal fibre.

Optically levitated micro- and nanoparticles offer an ideal playground for investigating photon-phonon interactions over macroscopic distances. Here we report the observation of long-range optical binding of multiple levitated microparticles, mediated by intermodal scattering and interference inside the evacuated core of a hollow-core photonic crystal fibre (HC-PCF). Three polystyrene particles with a diameter of 1 µm are stably bound together with an inter-particle distance of ~40 μm, or 50 times longer than the wavelength of the trapping laser. The levitated bound-particle array can be translated to-and-fro over centimetre distances along the fibre. When evacuated to a gas pressure of 6 mbar, the collective mechanical modes of the bound-particle array are able to be observed. The measured inter-particle distance at equilibrium and mechanical eigenfrequencies are supported by a novel analytical formalism modelling the dynamics of the binding process. The HC-PCF system offers a unique platform for investigating the rich optomechanical dynamics of arrays of levitated particles in a well-isolated and protected environment.This work was supported by Max Planck Society. R. Z. acknowledges funding from the Cluster of Excellence "Engineering of Advanced Materials" at the Friedrich-Alexander University in Erlangen, Germany

Octave-Spanning Supercontinuum Generation in As2S3–Silica Hybrid Waveguides Pumped by Thulium-Doped Fiber Laser

Broadband supercontinuum sources are of interest for various applications. The near-infrared region (1–3 μ m) is specifically useful for biomedical diagnostics. One of the promising media for supercontinuum generation in the infrared region is the strongly guiding nonlinear waveguide with an arsenic trisulfide core (As 2 S 3 ) and a fused silica cladding. The geometrical and chemical properties of such a waveguide allow to finely tune the dispersion landscape and nonlinearity through the core diameter variations. Here we report the generation of octave-spanning supercontinuum in As 2 S 3 -silica hybrid nanospike waveguides pumped by a thulium-doped all-fiber femtosecond laser and amplifier system at 1.9 μ m wavelength. The widest supercontinuum was obtained in the wavelength range from 1.1 to 2.5 μ m (full width at -10 dB) in the waveguide with a core diameter of 1.7 μ m. Generation of significant dispersive waves, as well as third harmonics component, is observed. Numerical simulation shows that the generated supercontinua are coherent in the entire spectral range and can be exploited to create a self-referenced laser comb

Detection of Gas Pipeline Leakage Using Distributed Optical Fiber Sensors: Multi-Physics Analysis of Leakage-Fiber Coupling Mechanism in Soil Environment

Optical fiber sensors are newly established gas pipeline leakage monitoring technologies with advantages, including high detection sensitivity to weak leaks and suitability for harsh environments. This work presents a systematic numerical study on the multi-physics propagation and coupling process of the leakage-included stress wave to the fiber under test (FUT) through the soil layer. The results indicate that the transmitted pressure amplitude (hence the axial stress acted on FUT) and the frequency response of the transient strain signal strongly depends on the types of soil. Furthermore, it is found that soil with a higher viscous resistance is more favorable to the propagation of spherical stress waves, allowing FUT to be installed at a longer distance from the pipeline, given the sensor detection limit. By setting the detection limit of the distributed acoustic sensor to 1 nε, the feasible range between FUT and the pipeline for clay, loamy soil and silty sand is numerically determined. The gas-leakage-included temperature variation by the Joule-Thomson effect is also analyzed. Results provide a quantitative criterion on the installation condition of distributed fiber sensors buried in soil for the great-demanding gas pipeline leakage monitoring applications

Mid-IR supercontinua in dispersion-engineered As2S3-silica nanospike waveguides pumped by fs pulses at 2.8 mu m

International audienceWe report generation of coherent octave-spanning mid-infrared supercontinua in As2S3-silica waveguides pumped by a custom-built 2.8 mu m femtosecond fiber laser. The fabricated hybrid waveguides are demonstrated to be long-term stable and water-resistant. (C) The Author(s

Editorial: Future directions in novel laser source development: Dynamical properties, and beam manipulation

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Octave-spanning Supercontinuum From As2S3-silica Double-nanospike Waveguide Pumped by Femtosecond Cr:ZnS Laser at 2.35 μm

We generate a 1.2 to 3.6 μm supercontinuum using a As2S3-silica double-nanospike waveguide pumped by femtosecond Cr:ZnS laser. Varying the core diameter allows the group velocity dispersion to be fine-tuned, thus maximizing supercontinuum bandwidth

Octave-Spanning Supercontinuum Generated in As2S3-Silica Waveguides Pumped by Tm-doped All-fibre MOPA

International audienceFiber-based supercontinuum sources in the mid-IR wavelength range are highly desirable for many applications [1] - [3] . Here we report the generation of octave-spanning supercontinua in As 2 S 3 -silica hybrid waveguides pumped by a thulium-doped all-fiber master-oscillator-power-amplifier (MOPA). The narrow As 2 S 3 core of the step-index waveguide has an extremely high nonlinearity, and by balancing its anomalous geometrical dispersion against the normal dispersion of the glass, the zero dispersion wavelength of the guided mode can be shifted towards the pump wavelength by suitable design. The \"nanospikes\" at both ends of the hybrid waveguide (see Fig. 1a ) are used to boost the launch efficiency into the fundamental core mode [3] , [4] . A thulium-doped all-fiber MOPA centred at 1.9 μm [5] , [6] was used as pump source. It emits pulses with a duration of 78 fs and a maximum peak power of 200 kW at a repetition rate of 23.8 MHz. Dual nanospike waveguides with core diameters d = 1.7 μm and 1.2 μm were tested in the experiment. The length of both waveguides was 3 mm. Fig. 1b plots the calculated dispersion parameter of the two waveguides. For d = 1.7 μm the pump lies within ~ 50 nm of a zero dispersion wavelength, in which case for a launched energy of ~32 pJ the measured spectrum at the output extends from 1.1 μm to 2.5 μm at the –10 dB level. The total output average power was measured as ~ 1.2 mW. When d = 1.2 μm, the pump wavelength lies in between two zero dispersion wavelengths, and for 23 pJ launched energy the spectrum extends from 1.7 μm to 2.3 μm, while a weak dispersive wave appears at 963 nm. In both cases the third harmonic components are visible at 630 nm (inset of Fig. 1c ), which fall within the bandgap of the As 2 S 3 material, limiting further increase of the pump energy. Numerically simulated spectra (black-dotted curves) calculated for the experimental pulse energy agree well with the measurements

Coherent octave-spanning mid-infrared supercontinuum generated in As₂S₃-silica double-nanospike waveguide pumped by femtosecond Cr:ZnS laser

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