Development of optical devices in a flat-fibre platform

Abstract

This thesis describes the development of optical devices in a novel flat-fibre platform. Device fabrication is achieved using direct grating writing and physical micromachining techniques.

A series of experimental studies have been undertaken in order to optimise the fabrication of UV-written waveguides and Bragg gratings in the flat-fibre geometry. The UV-writing parameters have been investigated including fluence and duty cycle, together with hydrogen loading and alignment factors. Loss measurements have been performed on a variety of passive and active structures using a novel distributed Bragg grating technique. The measured propagation loss of a channel waveguide based UV-written was 0.13 dB/cm ± 0.03 dB/cm.

Flat-fibre devices have been used as physical and refractive index sensors on a wedge flat-fibre structure. Through using UV-written Bragg gratings in series and parallel arrangement, it provides the capability of sensing two-dimensional bending and external refractive index variation in a single device.

Another passive device that has been developed in flat-fibre is the multimode interference (MMI) device. The concept of using two micro-machined trenches to fabricate the MMI device has also been discussed. In this work, a successful 1x3 MMI device has been fabricated by using a high precision dicing saw and the excess loss was measured as 1.89 dB.

Finally, the spectroscopy study of an erbium doped flat-fibre was performed. Absorption to about 0.32 dB/cm at 976 nm wavelength has been achieved in the erbium-doped flat-fibre. The first demonstration of signal amplification at wavelength of 1530 nm has been carried out where showing that the relative gain was 0.74 dB.

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Identifiers

ORCID for J.K. Sahu: orcid.org/0000-0003-3560-6152

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