Nonlinear optical processes in bulk and waveguide structures in the Infrared
McCarthy, John Edward
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The results of an experimental study into the third order nonlinear optical properties of chalcogenide glasses at a wavelength of 1550 nm are presented. Of the glasses investigated glass gallium lanthanum sulphide (GLS) was found to have an optical Kerr nonlinearity approximately 70 times higher than silica. Additionally the upper limit of GLS nonlinear absorption coefficient was measured to be over an order of magnitude smaller than the other chalcogenide glasses analysed. GLS was subsequently chosen as the host material for waveguide fabrication via ultrafast laser inscription. Near and mid infrared singlemode waveguide structures were successfully fabricated and their nonlinear guiding properties investigated. These investigations led to the generation of a supercontinuum from a singlemode waveguide that spanned over 3000 nm throughout the mid wavelength infrared spectral region. Studies into the contributing mechanisms of supercontinuum generation are presented in work conducted in silica based photonic crystal fibres with the extent of the supercontinuum generation being limited by the transmission range of silica. An investigation into saturable absorption effects in single walled carbon nanotubes is also presented. This study identified that for field irradiances on the order of 9.5×1013 W/m2 the contribution of multi-photon absorption exceeded that of saturable absorption.