The University of Southampton
University of Southampton Institutional Repository

Nonlinear properties of optical microfibres

Nonlinear properties of optical microfibres
Nonlinear properties of optical microfibres
Glass microfibre waveguides offer an intriguing platform for the investigation of nonlinear effects, due to their high effective nonlinearity which arises from the tight modal confinement down to dimensions comparable to the wavelength of guided light. This thesis presents theoretical and experimental work towards achieving efficient third and second harmonic generation in silica microfibres, as well as in microfibre loop resonators for enhancing the conversion. Since microfibre resonators themselves exhibit interesting nonlinear behaviour, the polarisation dependent properties of microcoil resonators were also studied. Efficient third harmonic generation is possible through intermodal phase matching, and experiments using short tapers have demonstrated significant efficiencies up to 10-3 over a uniform 4 mm waist. On the other hand, the interrogation of longer tapers, in which the harmonic generation occurs within the taper transition regions of several cm rather than the waist, allows for a broadband conversion observed to exceed 36 nm at the 5 dB bandwidth level. A straightforward technique to improve efficiency using microfibre loop resonators was also investigated. Near resonance, the recirculation of the pump power inside the resonator was experimentally shown to increase conversion by 7.7 dB higher than that of the straight microfibre, similar to simulated predictions, and by optimising the loop geometry the resonant efficiency enhancement can potentially reach 20 dB.
Simulations on second harmonic generation in microfibres indicate that the second order nonlinearity originates primarily from the structural anisotropy at the glass-air boundary (which exploits the high surface electric field strength of microfibres) as well as multipolar effects within the bulk. To overcome the inherent weakness of these effects, experiments focused on conversion enhancement via the aforementioned technique using loop resonators, with a measured 7.6 dB efficiency improvement.
In addition, an accurate polarisation dependent model for microcoils was developed for both the linear and nonlinear regimes by incorporating the effects of fibre twist and birefringence. The coupling between orthogonally polarised modes propagating along the microcoil results in a strongly polarisation sensitive transmission, especially near resonances, which in turn influences the nonlinear hysteresis characteristics.
Lee, Timothy
beb3b88e-3e5a-4c3f-8636-bb6de8040fcc
Lee, Timothy
beb3b88e-3e5a-4c3f-8636-bb6de8040fcc
Brambilla, Gilberto
815d9712-62c7-47d1-8860-9451a363a6c8

Lee, Timothy (2013) Nonlinear properties of optical microfibres. University of Southampton, Faculty of Physical Sciences and Engineering, Doctoral Thesis, 157pp.

Record type: Thesis (Doctoral)

Abstract

Glass microfibre waveguides offer an intriguing platform for the investigation of nonlinear effects, due to their high effective nonlinearity which arises from the tight modal confinement down to dimensions comparable to the wavelength of guided light. This thesis presents theoretical and experimental work towards achieving efficient third and second harmonic generation in silica microfibres, as well as in microfibre loop resonators for enhancing the conversion. Since microfibre resonators themselves exhibit interesting nonlinear behaviour, the polarisation dependent properties of microcoil resonators were also studied. Efficient third harmonic generation is possible through intermodal phase matching, and experiments using short tapers have demonstrated significant efficiencies up to 10-3 over a uniform 4 mm waist. On the other hand, the interrogation of longer tapers, in which the harmonic generation occurs within the taper transition regions of several cm rather than the waist, allows for a broadband conversion observed to exceed 36 nm at the 5 dB bandwidth level. A straightforward technique to improve efficiency using microfibre loop resonators was also investigated. Near resonance, the recirculation of the pump power inside the resonator was experimentally shown to increase conversion by 7.7 dB higher than that of the straight microfibre, similar to simulated predictions, and by optimising the loop geometry the resonant efficiency enhancement can potentially reach 20 dB.
Simulations on second harmonic generation in microfibres indicate that the second order nonlinearity originates primarily from the structural anisotropy at the glass-air boundary (which exploits the high surface electric field strength of microfibres) as well as multipolar effects within the bulk. To overcome the inherent weakness of these effects, experiments focused on conversion enhancement via the aforementioned technique using loop resonators, with a measured 7.6 dB efficiency improvement.
In addition, an accurate polarisation dependent model for microcoils was developed for both the linear and nonlinear regimes by incorporating the effects of fibre twist and birefringence. The coupling between orthogonally polarised modes propagating along the microcoil results in a strongly polarisation sensitive transmission, especially near resonances, which in turn influences the nonlinear hysteresis characteristics.

Text
Timothy Lee Thesis.pdf - Other
Available under License University of Southampton Thesis Licence.
Download (40MB)

More information

Published date: July 2013
Organisations: University of Southampton, Optoelectronics Research Centre

Identifiers

Local EPrints ID: 355529
URI: http://eprints.soton.ac.uk/id/eprint/355529
PURE UUID: 26d4ef24-b321-41b6-8212-36734e7b5507
ORCID for Timothy Lee: ORCID iD orcid.org/0000-0001-9665-5578
ORCID for Gilberto Brambilla: ORCID iD orcid.org/0000-0002-5730-0499

Catalogue record

Date deposited: 11 Nov 2013 14:07
Last modified: 15 Mar 2024 03:09

Export record

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×