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Liquid crystal adaptive planar optical devices

Liquid crystal adaptive planar optical devices
Liquid crystal adaptive planar optical devices
This thesis presents a series of experimental studies based on using liquid crystals (LC) with planar optical lightwave components. Adaptive optical devices have been fabricated by combining LCs with direct UV written buried channel waveguide and Bragg grating structures. It has been discovered that the hysteresis seen in previous LC tunable Bragg grating devices is due to a process known as the pincement transition. Pincement involves the transition from a splay-bend wall in the nematic LC to a pair of oppositely charged half-integer disclination lines. The voltage-based transient behaviour of the pincement transition correlated with the tuning curve response seen in voltage controlled LC tunable gratings. In order to reduce the hysteresis effect a new grooved substrate geometry was introduced. Rather than accessing the Bragg grating vertically via a wet etch process, the substrates are precision machined using a dicing saw to allow side access. The result is significantly reduced hysteresis, with a maximum tuning range of over 1nm with the application of under 30V(pp). Tunable chirped Bragg gratings based on standard PCB technology using arrays of resistors as heating elements were designed and tested. The group delay slope of the chirped gratings was tuned by 4ps/nm using a combination of heating elements and thermoelectric cooling. Finally, LC compounds were then tested for suitability as waveguiding media. It was found that both hollow fiber and planar substrate systems using an LC as the core guiding medium successfully guided both visible and IR light at telecomms wavelengths
University of Southampton
Snow, Benjamin D.
369fd679-066f-46db-9d5c-aecaa7179a6d
Snow, Benjamin D.
369fd679-066f-46db-9d5c-aecaa7179a6d
Smith, Peter
8979668a-8b7a-4838-9a74-1a7cfc6665f6
Kaczmarek, M.
408ec59b-8dba-41c1-89d0-af846d1bf327

Snow, Benjamin D. (2010) Liquid crystal adaptive planar optical devices. University of Southampton, Optoelectronics Research Centre, Doctoral Thesis, 247pp.

Record type: Thesis (Doctoral)

Abstract

This thesis presents a series of experimental studies based on using liquid crystals (LC) with planar optical lightwave components. Adaptive optical devices have been fabricated by combining LCs with direct UV written buried channel waveguide and Bragg grating structures. It has been discovered that the hysteresis seen in previous LC tunable Bragg grating devices is due to a process known as the pincement transition. Pincement involves the transition from a splay-bend wall in the nematic LC to a pair of oppositely charged half-integer disclination lines. The voltage-based transient behaviour of the pincement transition correlated with the tuning curve response seen in voltage controlled LC tunable gratings. In order to reduce the hysteresis effect a new grooved substrate geometry was introduced. Rather than accessing the Bragg grating vertically via a wet etch process, the substrates are precision machined using a dicing saw to allow side access. The result is significantly reduced hysteresis, with a maximum tuning range of over 1nm with the application of under 30V(pp). Tunable chirped Bragg gratings based on standard PCB technology using arrays of resistors as heating elements were designed and tested. The group delay slope of the chirped gratings was tuned by 4ps/nm using a combination of heating elements and thermoelectric cooling. Finally, LC compounds were then tested for suitability as waveguiding media. It was found that both hollow fiber and planar substrate systems using an LC as the core guiding medium successfully guided both visible and IR light at telecomms wavelengths

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Published date: December 2010
Organisations: University of Southampton, Optoelectronics Research Centre

Identifiers

Local EPrints ID: 194997
URI: http://eprints.soton.ac.uk/id/eprint/194997
PURE UUID: ff134481-d86b-455c-a216-85174c3968a8
ORCID for Peter Smith: ORCID iD orcid.org/0000-0003-0319-718X

Catalogue record

Date deposited: 17 Aug 2011 10:25
Last modified: 30 Jan 2020 01:27

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