Functionalised optical fibre devices with embedded electrodes for nonlinear photonics

Abstract

In this thesis are reported progresses in the development of a technique known as thermal poling of silica fibres, which allows for the creation of an effective second order nonlinearity in materials, such as glasses, which naturally lack any second order susceptibility. The main part of the thesis work was devoted to the exploration of new experimental methods as well as numerical simulations to overcome some of the apparently intrinsic limits shown by the thermal poling technique so far, such as for example the length of the nonlinear devices and the complexity of the geometrical structure of microstructured optical fibres, both solid and hollow-core. A new poling method, based on electrostatic induction, was developed and numerically modelled which allows for poling an optical fibre without any physical contact between the source of the electric potential and the electrode embedded into the fibre. Furthermore different kinds of materials (both metallic and non-metallic) have been used to create the embedded electrodes, and in particular a new method for poling metre-long optical fibres by means of aqueous solutions used as electrodes was developed. Using together both the induction poling method with liquid embedded electrodes could allow for poling metre-long fibres and microstructured fibres of very complex geometry which could raise the second harmonic efficiency up to a value of four order of magnitude higher than the one obtained in common step-index doped fibres. Part of this thesis was dedicated to the functionalisation of different kinds of silica fibres (including microstructured hollow core fibres) by means of deposition of thin layers of semiconductors (such as silicon, germanium or zinc selenide), with the aim of exploiting their intrinsic nonlinearities to increase the whole effective second order nonlinearity of an all- fibre nonlinear device.

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Identifiers

ORCID for Pier-John Sazio: orcid.org/0000-0002-6506-9266

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