ORCID Profile
0000-0001-6075-2587
Current Organisation
University of Oxford
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Publisher: SPIE
Date: 09-02-2012
DOI: 10.1117/12.909324
Publisher: The Optical Society
Date: 21-09-2011
DOI: 10.1364/OME.1.001127
Publisher: Springer Science and Business Media LLC
Date: 19-01-2015
DOI: 10.1038/NCOMMS6977
Abstract: Metamaterials are a promising new class of materials, in which sub-wavelength physical structures, rather than variations in chemical composition, can be used to modify the nature of their interaction with electromagnetic radiation. Here we show that a metamaterials approach, using a discrete physical geometry (conformation) of the segments of a polymer chain as the vector for a substantial refractive index change, can be used to enable visible wavelength, conjugated polymer photonic elements. In particular, we demonstrate that a novel form of dip-pen nanolithography provides an effective means to pattern the so-called β-phase conformation in poly(9,9-dioctylfluorene) thin films. This can be done on length scales ≤500 nm, as required to fabricate a variety of such elements, two of which are theoretically modelled using complex photonic dispersion calculations.
Publisher: SPIE
Date: 10-02-2011
DOI: 10.1117/12.875757
Publisher: IEEE
Date: 06-2016
Publisher: American Chemical Society (ACS)
Date: 25-02-2013
DOI: 10.1021/NL400134V
Abstract: We demonstrate the realization of confined surface plasmon polariton lifiers using a thin layer of the organic gain medium 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran dispersed in a tris(8-hydroxy-quinolinato)aluminum matrix. Complete loss compensation, which occurs at a pump fluence of approximately 200 μJ/cm(2), is directly observed in the time domain and studied for a range of waveguide lengths. The power dependence is also reported, and a significant net gain of 93 dB/mm is observed at the highest fluence.
Publisher: Wiley
Date: 19-01-2011
DOI: 10.1002/PIP.1069
Publisher: IOP Publishing
Date: 11-06-2013
Publisher: AIP Publishing
Date: 15-10-2005
DOI: 10.1063/1.2085311
Abstract: We report the solid-state optical gain characteristics of a spiroanthracenefluorene polymer, namely, poly(9-spiro(10,10-bis(2-ethylhexyl)-10H-anthracene)fluorene) (PEHSAF), specifically designed for thermal stability. An efficient stimulated emission occurs at λ=445nm under lified spontaneous emission conditions for asymmetric slab waveguide structures. The modal gain and propagation loss coefficients were found to be g⩽38cm−1 and α=0.8cm−1, respectively. The PEHSAF stimulated emission characteristics are shown to be thermally stable in vacuo for temperatures up to 250 °C. Surface-emitting distributed feedback lasers have been fabricated by spin-coating PEHSAF onto one-dimensional grating structures. The lasers operate in the blue spectral region and exhibit low oscillation thresholds (⩾18nJ) and relatively high slope efficiencies (⩽5%). Varying the PEHSAF film thickness allows the tuning of the emission wavelength within a 16 nm window.
Publisher: IOP Publishing
Date: 24-05-2016
Publisher: SPIE
Date: 16-03-2015
DOI: 10.1117/12.2077573
Publisher: American Chemical Society (ACS)
Date: 02-11-2011
DOI: 10.1021/NN203754V
Abstract: The use of plasmonic nanostructures for the removal of unwanted long-lived states is investigated. We show that the total decay rate of such a state can be increased by up to 4 orders of magnitude, as compared to its intrinsic radiative decay rate, while leaving other neighboring optical transitions unaffected. For the specific case of molecular triplet excited states, we show that the use of a "plasmonic sink" has the potential to reduce photobleaching and ground-state depletion by at least 2 orders of magnitude. We consider, in addition, the impact of such structures on the performance of organic semiconductor lasers and show that, under realistic device conditions, plasmonic sinks have the capacity to increase the achievable laser repetition rate by a factor equal to the triplet decay rate enhancement. We conclude by studying the effect of exciton diffusion on the triplet density in the presence of metallic nanoparticles.
Publisher: IEEE
Date: 06-2011
Publisher: SPIE
Date: 25-03-2013
DOI: 10.1117/12.2005332
Publisher: AIP Publishing
Date: 25-07-2011
DOI: 10.1063/1.3619169
Abstract: We demonstrate that coherent random lasing can occur in solid-state dispersions of laser dyes 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran and 4-dicyanomethylene-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran within a tris(8-hydroxy-quinolinato)aluminum matrix without the need for infiltrated scatterers. Random lasing thresholds as low as 90 μJ/cm2 are observed in 250 nm-thick films with 2-2.5% dye concentration. We find that the lasing threshold exhibits a power law decay with s le area, providing a simple test for the occurrence of random lasing. We discuss the implications of this result in the context of previous reports of lasing in these materials where feedback was provided by conventional optical resonators.
Publisher: IEEE
Date: 05-2011
Publisher: IEEE
Date: 06-2010
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Paul Stavrinou.