1,721,001 research outputs found
Dataset for All-fiber fourth and fifth harmonic generation from a single source
No full textRaw data for figures in Abdul Khudus, Muhammad, Lee, Timothy, De Lucia, Francesco, Corbari, Constantino, Sazio, Pier-John, Horak, Peter and Brambilla, Gilberto (2016) All-fiber fourth and fifth harmonic generation from a single source. Optics Express, 24, (19), 21777-21793. (doi:10.1364/OE.24.021777)</span
Ultraviolet generation in step index optical fibres and microfibres
No full textCoherent ultraviolet (UV) generation has various applications in a large number of fields, such as stand-off explosive detection, enhanced Raman scattering and photolithography, to name a few. Typically, the generation of coherent UV light relied on frequency doubling with nonlinear crystals and relatively complicated free space optics, on toxic gases (excimers) and low power UV diodes. In this thesis, the use of solid core step-index optical fibre for the generation of coherent UV radiation is investigated. Here, wavelength conversion in optical microfibres (OMFs) via nonlinear processes is considered. Firstly, efficient generation of UV radiation via intermodal third harmonic generation (THG) in fibres is first studied. While THG is potentially efficient in OMFs, it is not feasible in optical fibres with large numerical apertures. Detuning is found to be a critical parameter which determines the overall efficiency, thereby making the OMF diameter control crucial. Initial experiments indicate that the quasi-continuous wave (CW) sources with long pulses (a few ns) and high peak powers (∼ kW) are the most suitable for intermodal THG in OMFs, as detrimental nonlinear effects become dominant with ultrashort pulses. However, further theoretical investigations show that intermodal THG is fundamentally limited by the intrinsic surface roughness of the silica OMFs, restricting the maximum efficiency to ∼ 10-3. This leads to the investigation of four wave mixing (FWM), where both parametric amplification and wavelength generation are theoretically investigated. A quasi-CW source working in conjunction with a periodically poled silica fibre (PPSF) is employed to investigate this experimentally, and it is shown that a scheme employing two OMFs allowed the generation of coherent UV radiation down to 0:31 µm, with fundamental limitations being imposed from losses due to the oxygen-deficiency centre inherent to the fibre
Effect of intrinsic surface roughness on the efficiency of intermodal phase matching in silica optical nanofibers
Full text linkWe investigate the effect of intrinsic surface roughness associated to frozen thermal oscillations from the fiber fabrication process on the efficiency of third-harmonic generation via intermodal phase matching in silica nanofibers. Already a periodic wave with roughness of 0.2 nm reduces the efficiency by roughly 50% in a 1-mm optical nanofiber, with the divergence growing quadratically with distance. The surface wave period does not exhibit a large impact on the efficiency, due to averaging effects. However, both the location of the surface waves with respect to the phase matching radius as well as the surface wave amplitude have substantial effect on the efficiency, with the former presenting the possibility of transferring the power back to the pump wavelength. Simulations with a realistic superposition of random surface waves indicate that the conversion efficiency increases only for a few mm of propagation and reaches a maximum of less than 1%
Fundamental-mode third harmonic generation in microfibers by pulse-induced quasi-phase matching
No full textA scheme to enhance the fundamental-mode third harmonic generation efficiency in microfibers is presented. By introducing an appropriate counter-propagating pulse train, large propagation constant mismatch is partly overcome and nonlinear phase shifts could be corrected for, thus quasi-phase matching between the fundamental pump mode and the fundamental third harmonic mode is achieved, enabling the harmonic power to grow along the direction of propagation. Depending on the microfiber and pulse parameters, phase matching can enhance the conversion efficiency by several orders of magnitude with respect to the non-phase matched case. This scheme offers an alternative approach for harmonic generation and could potentially be applied to other small core waveguides
Phase matched parametric amplification via four-wave mixing in optical microfibers
No full textFour-wave mixing (FWM) based parametric amplification in optical microfibers (OMF) is demonstrated over a wavelength range of over 1000 nm by exploiting their tailorable dispersion characteristics to achieve phase matching. Simulations indicate that for any set of wavelengths satisfying the FWM energy conservation condition there are two diameters at which phase matching in the fundamental mode can occur. Experiments with a high-power pulsed source working in conjunction with a periodically poled silica fiber (PPSF), producing both fundamental and second harmonic signals, are undertaken to investigate the possibility of FWM parametric amplification in OMFs. Large increases of idler output power at the third harmonic wavelength were recorded for diameters close to the two phase matching diameters. A total amplification of more than 25 dB from the initial signal was observed in a 6 mm long optical microfiber, after accounting for the thermal drift of the PPSF and other losses in the system
Harmonic generation via chi3 intermodal phase matching in microfibers
No full textIntermodally phase matched up- and down-conversion processes based on the third order nonlinearity have been proposed to efficiently generate light in the UV and mid-IR wavelength regions in solid core silica optical fibers and optical microfibers. We study waveguide parameters and practical considerations required for optimum conversion
OAM beam generation using all-fiber fused couplers
No full textWe demonstrate the orbital angular momentum (OAM) beam generation using an all-fiber fused coupler based on single mode fiber (SMF) and air-core fiber. The fabricated device is directly SMF compatible with ~80% power coupling efficiency
Dataset for Harmonic Generation via chi(3) Intermodal Phase Matching in Microfibers
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OAM Generation in optical fibre and free space devices
No full textOrbital angular momentum (OAM) beam generation has been investigated using all-fibre and free space configurations. In the first approach, the composite fused coupler is based on a single mode fibre (SMF) and an air-core fibre. The second approach exploits geometrical phase introduced by nanostructuring of silica glass. Both approaches are demonstrated to achieve power coupling efficiencies in excess of 80% at telecom wavelengths
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