Experimental study of quantum dot and dash lasers

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dc.contributor.advisor Osborne, Simon en
dc.contributor.advisor O'Reilly, Eoin P. en
dc.contributor.author Heck, Susannah C.
dc.date.accessioned 2013-04-09T09:17:53Z
dc.date.available 2013-04-09T09:17:53Z
dc.date.issued 2009
dc.date.submitted 2009
dc.identifier.citation Heck, S. C. 2009. Experimental study of quantum dot and dash lasers. PhD Thesis, University College Cork. en
dc.identifier.uri http://hdl.handle.net/10468/1036
dc.description.abstract Quantum dashes are elongated quantum dots. Polarized edge-photovoltage and spontaneous emission spectroscopy are used to study the anisotropy of optical properties in 1.5μm InGaAsP and AlGaInAs-based quantum dash lasers. Strain, which causes TM-polarized transitions to be suppressed at the band edge, coupled with carrier confinement and dash shape leads to an enhancement of the optical properties for light polarized along the dash long axis, in excellent agreement with theoretical results. An analysis of the integrated facet and spontaneous emission rate with total current and temperature reveals that, in both undoped and p-doped InGaAsP-based quantum dash lasers at room temperature, the threshold current and its temperature dependence remain dominated by Auger recombination. We also identify two processes which can limit the output power and propose that the effects of the dopant in p-doped InGaAsP-based lasers dominate at low temperature but decrease with increasing temperature. A high threshold current density in undoped AlGaInAs-based quantum dash laser samples studied, which degrade rapidly at low temperature, is not due to intrinsic carrier recombination processes. 1.3μm GaAs-based quantum dots lasers have been widely studied, but there remains issues as to the nature of the electronic structure. Polarized edge-photovoltage spectroscopy is used to investigate the energy distribution and nature of the energy states in InAs/GaAs quantum dot material. A non-negligible TM-polarized transition, which is often neglected in calculations and analyses, is measured close to the main TE-polarized ground state transition. Theory is in very good agreement with the experimental results and indicates that the measured low-energy TM-polarized transition is due to the strong spatial overlap between the ground state electron and the light-hole component of a low-lying excited hole state. Further calculations suggest that the TM-polarized transition reduces at the band edge as the quantum dot aspect ratio decreases. en
dc.description.sponsorship European Commission (FP6-NMP 017140 ZODIAC (Zero Order Dimension based Industrial components Applied to teleCommunications) ) en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.relation.uri http://library.ucc.ie/record=b1894212
dc.rights © 2009, Susannah C. Heck en
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/3.0/ en
dc.subject Diode Laser en
dc.subject Quantum dashes en
dc.subject Spontaneous emission spectroscopy en
dc.subject TM-polarized transitions en
dc.subject InGaAsP en
dc.subject AlGaInAs en
dc.subject Auger recombination en
dc.subject GaAs en
dc.subject Polarized edge-photovoltage spectroscopy en
dc.subject TE-polarized ground state transition en
dc.subject Quantum dot en
dc.subject.lcsh Quantum dots en
dc.subject.lcsh Lasers en
dc.title Experimental study of quantum dot and dash lasers en
dc.type Doctoral thesis en
dc.type.qualificationlevel Doctoral en
dc.type.qualificationname PhD (Science) en
dc.internal.availability Full text available en
dc.check.info No embargo required en
dc.description.version Accepted Version
dc.contributor.funder Science Foundation Ireland en
dc.contributor.funder European Commission en
dc.description.status Not peer reviewed en
dc.internal.school Physics en
dc.check.type No Embargo Required
dc.check.reason No embargo required en
dc.check.opt-out Not applicable en
dc.thesis.opt-out false *
dc.check.embargoformat Not applicable en
ucc.workflow.supervisor alancollins@ucc.ie *

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