Investigation of highly symmetric photonic quasi-crystals
Investigation of highly symmetric photonic quasi-crystals
Photonic band gap (PBG) devices have many optical applications including filtering, wave guiding, optical time delay and light extraction. 2D Periodic photonic crystals (PC) are limited to six-fold rotational symmetry (hexagonal lattice) this in turn limits the isotropy of the PBG. Most applications would benefit from more isotropic properties allowed by photonic quasi-crystals (PQC): for waveguide bends a high symmetry allows a greater choice of bend angle; it is expected that increasing the order of symmetry will flatten the dispersion bands and therefore provide use with greater reduction of group velocity, also the greater isotropy of the device would increase the beam uniformity for out-coupling applications.
Various highly symmetric geometries were investigated, Fibonacci spirals were biometrically inspired from seed heads of plants such as the sunflower and show quasi-infinite rotational symmetry; another quasi-infinitely symmetric pattern is the pinwheel tiling of the plane invented by John Conway, this uses a right angled triangle with side lengths of 1,2 and √5 as the proto-tile which can then be iteratively dissected into 5 identical triangles, each triangle is rotated by an irrational angle with respect to π. Also, a totally new breed of quasicrystal pattern was developed using an inverse Fourier transform method where it is possible to obtain any number of even symmetries. The symmetry of all these PQCs was confirmed by the simulation of their diffraction pattern. Also, the finite different time domain method allowed the modelling of the transmission and reflection properties of the devices, which showed that they have highly isotropic properties.
Both pinwheel and Fibonacci spiral devices were fabricated by etching nanometre scale air holes into planar waveguides using standard micro-fabrication techniques, the fabrication process is described in detail. The fabricated devices were designed to operate in the visible and near infrared part of the electromagnetic spectrum. They were subsequently optically tested for their transmission and out-coupling properties. The isotropy of the PBG was confirmed and it was also shown that the ultra high symmetry allows light out-coupling with unprecedented uniformity. The pinwheel PQCs also showed properties which are indicative of Anderson localisation.
University of Southampton
Lee, Thomas David Matthew
2006
Lee, Thomas David Matthew
Lee, Thomas David Matthew
(2006)
Investigation of highly symmetric photonic quasi-crystals.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Photonic band gap (PBG) devices have many optical applications including filtering, wave guiding, optical time delay and light extraction. 2D Periodic photonic crystals (PC) are limited to six-fold rotational symmetry (hexagonal lattice) this in turn limits the isotropy of the PBG. Most applications would benefit from more isotropic properties allowed by photonic quasi-crystals (PQC): for waveguide bends a high symmetry allows a greater choice of bend angle; it is expected that increasing the order of symmetry will flatten the dispersion bands and therefore provide use with greater reduction of group velocity, also the greater isotropy of the device would increase the beam uniformity for out-coupling applications.
Various highly symmetric geometries were investigated, Fibonacci spirals were biometrically inspired from seed heads of plants such as the sunflower and show quasi-infinite rotational symmetry; another quasi-infinitely symmetric pattern is the pinwheel tiling of the plane invented by John Conway, this uses a right angled triangle with side lengths of 1,2 and √5 as the proto-tile which can then be iteratively dissected into 5 identical triangles, each triangle is rotated by an irrational angle with respect to π. Also, a totally new breed of quasicrystal pattern was developed using an inverse Fourier transform method where it is possible to obtain any number of even symmetries. The symmetry of all these PQCs was confirmed by the simulation of their diffraction pattern. Also, the finite different time domain method allowed the modelling of the transmission and reflection properties of the devices, which showed that they have highly isotropic properties.
Both pinwheel and Fibonacci spiral devices were fabricated by etching nanometre scale air holes into planar waveguides using standard micro-fabrication techniques, the fabrication process is described in detail. The fabricated devices were designed to operate in the visible and near infrared part of the electromagnetic spectrum. They were subsequently optically tested for their transmission and out-coupling properties. The isotropy of the PBG was confirmed and it was also shown that the ultra high symmetry allows light out-coupling with unprecedented uniformity. The pinwheel PQCs also showed properties which are indicative of Anderson localisation.
This record has no associated files available for download.
More information
Published date: 2006
Identifiers
Local EPrints ID: 465913
URI: http://eprints.soton.ac.uk/id/eprint/465913
PURE UUID: 55f377fd-2581-4bc7-96bb-2d1dcd87d36d
Catalogue record
Date deposited: 05 Jul 2022 03:32
Last modified: 05 Jul 2022 03:32
Export record
Contributors
Author:
Thomas David Matthew Lee
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