960 research outputs found
One- and two-photon pumped organic semiconductor lasers
No full textThis thesis describes a number of studies on organic semiconductors focused around using them as gain media for lasers. The photophysical properties of organic semiconductors are studied using a wide range of experimental techniques, allowing the evaluation of new materials and novel excitation schemes for use in organic semiconductor lasers.
Polyfluorene is a well-established conjugated polymer laser gain medium and in this thesis its excellent lasing properties are combined with its two photon absorption properties to demonstrate a tunable two-photon pumped solid-state laser based on a commercially available organic semiconductor.
A family of bisfluorene dendrimers was studied using a number of photophysical techniques to evaluate their potential as laser materials. Distributed feedback lasers based on one of the dendrimers are demonstrated with lasing thresholds comparable to polyfluorene. The same materials were found to have enhanced two-photon absorption properties in comparison to polyfluorene, leading to the fabrication of tunable two-photon pumped dendrimer lasers.
A member of a novel family of star-shaped oligofluorene truxenes was evaluated as a laser gain material and the distributed feedback lasers made from them show some of the lowest lasing thresholds reported for organic semiconductors, partly as a consequence of exceptionally low waveguide losses in comparison to other single-material thin films.
Finally, an organic laser dye is blended with a conjugated polymer, where the dye molecules harvest the excitation light of a GaN laser diode and transfer its energy to the polymer molecules. This is the first time such a scheme is used in an organic laser and in combination with a novel surface-emitting distributed Bragg reflector resonator allows the demonstration of a diode-pumped organic laser, a significant step towards simplifying organic lasers
Measuring nitroaromatic explosives using polymer-coated microstructured optical fibers
No full textOral presentation in Technical Session 3- Chemical and material sensing. Tuesday 10 December 1400–1230Fenghong Chu, Georgios Tsiminis, Catherine E. Lang, Nigel A. Spooner and Tanya M. Monr
Novel imaging tools for investigating the role of immune signalling in the brain
No full textAbstract not availableJonathan Henry W. Jacobsen, Lindsay M. Parker, Arun V. Everest-Dass, Erik P. Schartner, Georgios Tsiminis, Vasiliki Staikopoulos, Mark R. Hutchinson, Sanam Mustaf
Extruded soft glass single-ring hollow core fibres
No full textOral presentation in Technical Session 2 - Fibre and Waveguide Technologies. Wednesday 11 December 1400-1530Kristopher J. Rowland, Heike Ebendorff-Heidepriem, Shahraam Afshar, Georgios Tsiminis and Tanya M. Monr
Explosives sensing based on suspended core fiber coated with conjugated polymer
No full textSuspended core fibers with voids surrounding the core coated with conjugate polymer were used to detect nitroaromatic explosives based on the fluorescence quenching technique. The background Raman signal from a suspended core fiber was used as reference to optimize coupled into the core of the fiber. The fluorescence spectra were integrated across all wavelengths to extract the integrated fluorescence intensity at regular time intervals. Fluorescence decay lifetimes were obtained by fitting a single exponential decay and were used to detect 1,4-dinitrobenzene (DNB), a member of the nitroaromatics family of explosives, in acetone solutions at concentrations as low as 6.3 ppm.Fenghong Chu, Georgios Tsiminis, Nigel A. Spooner and Tanya M. Monr
Quantification of the fluorescence sensing performance of microstructured optical fibers compared to multi-mode fiber tips
No full textPublished 3 Aug 2016Microstructured optical fibers, particularly those with a suspended-core geometry, have frequently been argued as efficient evanescent-field fluorescence-based sensors. However, to date there has not been a systematic comparison between such fibers and the more common geometry of a multi-mode fiber tip sensor. In this paper we make a direct comparison between these two fiber sensor geometries both theoretically and experimentally. Our results confirm that suspended-core fibers provide a significant advantage in terms of total collected fluorescence signal compared to multi-mode fibers using an equivalent experimental configuration.Erik P. Schartner, Georgios Tsiminis, Matthew R. Henderson, Stephen C. Warren-Smith, and Tanya M. Monr
A two-photon pumped polyfluorene laser
No full textAbstract not availableGeorgios Tsiminis, Arvydas Ruseckas, Ifor D. W. Samuel, and Graham A. Turnbul
Explosives detection by fluorescence quenching of conjugated polymers in suspended core optical fibers
No full textIn this work we demonstrate a suspended core microstructured optical fiber-based sensor platform forexplosives detection based on the fluorescence quenching of a surface-attached conjugated polymerpoly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV). These fibers allow for strongevanescent field interactions with the surrounding media because of their small core size, and can sam-ple minute liquid volumes. This is the first demonstration of a fluorescent conjugated polymer sensorcapable of measuring liquid explosives samples loaded within an optical fiber. This technique is used toidentify 1,4-dinitrobenzene (DNB), a member of the nitroaromatics family of explosives, in acetone forconcentrations as low as 6.3 ppm in a total sampling volume of 27 nl and to quantify its concentrationusing the fluorescence decay lifetime, requiring an analysis time of only a few minutes.Fenghong Chu, Georgios Tsiminis, Nigel A. Spooner, Tanya M. Monr
Portable optical fiber probe for in vivo brain temperature measurements
No full textThis work reports on the development of an optical fiber based probe for in vivo measurements of brain temperature. By utilizing a thin layer of rare-earth doped tellurite glass on the tip of a conventional silica optical fiber a robust probe, suitable for long-term in vivo measurements of temperature can be fabricated. This probe can be interrogated using a portable optical measurement setup, allowing for measurements to be performed outside of standard optical laboratories.Stefan Musolino, Erik P. Schartner, Georgios Tsiminis, Abdallah Salem, Tanya M. Monro, and Mark R. Hutchinso
Identification and quantification of explosives in nanolitre solution volumes by Raman spectroscopy in suspended core optical fibers
No full textA novel approach for identifying explosive species is reported, using Raman spectroscopy in suspended core optical fibers. Numerical simulations are presented that predict the strength of the observed signal as a function of fiber geometry, with the calculated trends verified experimentally and used to optimize the sensors. This technique is used to identify hydrogen peroxide in water solutions at volumes less than 60 nL and to quantify microgram amounts of material using the solvent’s Raman signature as an internal calibration standard. The same system, without further modifications, is also used to detect 1,4-dinitrobenzene, a model molecule for nitrobenzene-based explosives such as 2,4,6-trinitrotoluene (TNT).Georgios Tsiminis, Fenghong Chu, Stephen C. Warren-Smith, Nigel A. Spooner and Tanya M. Monr
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