Ahmadou Wague

Bio: Ahmadou Wague is an academic researcher. The author has contributed to research in topics: Supercontinuum & Photonic-crystal fiber. The author has an hindex of 5, co-authored 6 publications receiving 160 citations.

Super-flat coherent supercontinuum source in As 38.8 Se 61.2 chalcogenide photonic crystal fiber with all-normal dispersion engineering at a very low input energy.

Abstract: We numerically report super-flat coherent mid-infrared supercontinuum (MIR-SC) generation in a chalcogenide As38.8Se61.2 photonic crystal fiber (PCF). The dispersion and nonlinear parameters of As38.8Se61.2 chalcogenide PCFs by varying the diameter of the air holes are engineered to obtain all-normal dispersion (ANDi) with high nonlinearities. We show that launching low-energy 50 fs optical pulses with 0.88 kW peak power (corresponding to pulse energy of 0.05 nJ) at a central wavelength of 3.7 μm into a 5 cm long ANDi-PCF generates a flat-top coherent MIR-SC spanning from 2900 to 4575 nm with a high spectral flatness of 3 dB. This ultra-wide and flattened spectrum has excellent stability and coherence properties that can be used for MIR applications such as medical diagnosis of diseases, atmospheric pollution monitoring, and drug detection.

Ultraflat-top midinfrared coherent broadband supercontinuum using all normal As2S5-borosilicate hybrid photonic crystal fiber

Abstract: We report more than two octave spanning mid-IR flat-top supercontinuum (SC) generation using all normal As2S5-borosilicate hybrid photonic crystal fiber Our design is based on a chalcogenide As2S5 photonic crystal fiber (PCF), where the first ring composed of six air holes is made by borosilicate glass By injecting 50-fs pulses with 16 nJ energy at 25 μm in the all normal dispersion (ANDi) regime, a flat-top broadband SC extending from 1 to 5 μm with high-spectral flatness of 8 dB is obtained in only 4-mm fiber length To the best of our knowledge, we present the broadest flat mid-IR spectrum generated in the ANDi regime of an optical fiber The self-phase modulation and the optical wave breaking are identified as the main broadening mechanisms The obtained broadband light source can be potentially used in the field of spectroscopy and in high-resolution optical coherent tomography owing to the high-spectral SC flatness generated by our designed fiber

Numerical investigation of an ultra-broadband coherent mid-infrared supercontinuum in a chalcogenide AsSe2-As2S5 multimaterial photonic crystal fiber

Abstract: In this paper, we report on the simulation of an ultra-broadband coherent mid-infrared supercontinuum (SC) extending from 1.25 to 20 μm generated using a novel AsSe2-As2S5 multimaterial photonic crystal fiber (PCF). The proposed fiber is composed of a core made of AsSe2 glass and a surrounding cladding made of As2S5 glass. The hybrid PCF is designed to have a zero-dispersion wavelength (ZDW) of 3.3 μm with an overall highly engineered group velocity dispersion shifted to the mid-infrared wavelength region. The SC is generated by pumping 50 fs pulses at 4 μm emitted from an optical parameter amplifier with low energy of 0.625 nJ. The pumping wavelength is selected in the anomalous dispersion regime close to the ZDW. The widening of the SC is mainly based on the soliton effects in the anomalous dispersion region combined with self-phase modulation, cross-phase modulation, stimulated Raman scattering, four-wave mixing, and dispersive wave. The obtained SC shows a high degree of coherence and a 15 fs temporal compressed pulse is generated in only 5 mm long AsSe2-As2S5 hybrid PCF. The power proportion of the SC generated beyond 4 μm is 98% with its long wavelength edge up to 20 μm. To the best of our knowledge, the obtained SC is the first broadest spectrum reported in the mid-infrared region with very low energy. Our results highlight the potential of the novel chalcogenide AsSe2-As2S5 multimaterial PCF to emit across the ultra-broadband mid-infrared atmospheric windows and the molecular fingerprint region.

Ultra-broadband, coherent mid-IR supercontinuum expanding from 1.5 to 12.2 μm in new design of AsSe2 photonic crystal fibre

Abstract: We propose a new design of AsSe2 photonic crystal fibre (PCF) with all-normal dispersion, nearly zero flat-top used to generate an ultra-broadband supercontinuum spanning from 1.5 to 12.2 μm. Simulated results show that, when we use only 1 mm of AsSe2 PCF, a broadband mid-infrared supercontinuum with the specrum extent from 1.5 to 12.2 μm is obtained with a very low input energy of E = 1.3 nJ at the wavelength of 3.5 μm and pulse duration of 100 fs. We study the temporel and spectral impact of optical wave breaking in the development of the continuum. The influence of the fibre length, the input energy and the full width at half maximum is investigated. Compared to previous research works, we have obtained the broadest, coherent supercontinuum, which could be applicable in biomolecular sensing, cancer diagnostics, infrared spectroscopy and free space communication.

Supercontinuum generation, photonic crystal fiber

Abstract: A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Super-flat coherent supercontinuum source in As 38.8 Se 61.2 chalcogenide photonic crystal fiber with all-normal dispersion engineering at a very low input energy.

Abstract: We numerically report super-flat coherent mid-infrared supercontinuum (MIR-SC) generation in a chalcogenide As38.8Se61.2 photonic crystal fiber (PCF). The dispersion and nonlinear parameters of As38.8Se61.2 chalcogenide PCFs by varying the diameter of the air holes are engineered to obtain all-normal dispersion (ANDi) with high nonlinearities. We show that launching low-energy 50 fs optical pulses with 0.88 kW peak power (corresponding to pulse energy of 0.05 nJ) at a central wavelength of 3.7 μm into a 5 cm long ANDi-PCF generates a flat-top coherent MIR-SC spanning from 2900 to 4575 nm with a high spectral flatness of 3 dB. This ultra-wide and flattened spectrum has excellent stability and coherence properties that can be used for MIR applications such as medical diagnosis of diseases, atmospheric pollution monitoring, and drug detection.

A Review of Mid-Infrared Supercontinuum Generation in Chalcogenide Glass Fibers

Abstract: Chalcogenide glasses have the advantages of a wide transparency window (over 20 μm) and high optical nonlinearity (up to a thousand times greater than that of silica glasses), making them good candidates for mid-infrared supercontinuum generation. In this review, we describe both the history and recent developments in mid-infrared supercontinuum generation from chalcogenide fibers according to three kinds of fiber structures: step-index, microstructured and tapered fibers. We also review the coherence properties of mid-infrared supercontinuum generation and all-fiber supercontinuum sources based on chalcogenide fibers.