Browsing by Author "DONEGAN, JOHN FRANCIS"
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6 x 6 Effective Mass Hamiltonian for Heterostructures grown on (11N)-oriented substrates
DONEGAN, JOHN FRANCIS (American Physical Society, 2003)The 6?6 effective mass Hamiltonian for semiconductor heterostructures grown on (11N)-oriented substrates is derived and is compared with the 4?4 model. The hole subbands of InGaAs/InP single quantum wells grown on ... -
Analysis of slot characteristics in single mode semiconductor lasers using the 2D scattering matrix method
DONEGAN, JOHN FRANCIS (IEEE, 2006)We use the two-dimensional (2-D) scattering matrix method (SMM) to analyze the slot characteristics in slotted single-mode semiconductor lasers and compare the results with those calculated by the one-dimensional transfer ... -
Calculation of gain?current characteristics in ZnCdSe?ZnSe quantum well structures including many body effects.
DONEGAN, JOHN FRANCIS; HEGARTY, JOHN (American Institute of Physics, 1996)The gain-spontaneous recombination characteristics have been calculated for a 40 ? Zn0.8Cd0.2Se-ZnSe quantum well including many body effects. We examine the effect of the inclusion of the Coulomb enhancement on the gain ... -
Confined optical modes and amplified spontaneous emission from a microtube cavity formed by vacumm assisted filtration
GOUNKO, IOURI; DONEGAN, JOHN FRANCIS; PEROVA, TANIA; RAKOVICH, YURY (American Physical Society, 2006)The authors demonstrate a new route to the fabrication of individual aluminosilicate microtubes that can act as micron-scale optical cylindrical resonators. The microtubes were prepared using a simple vacuum assisted wetting ... -
Determination of internal loss and quasi-fermi level separation from the amplified spontaneous emission (ASE) spectrum of Fabry-Perot (FP) semiconductor lasers
DONEGAN, JOHN FRANCIS (IEEE, 2006)The net modal gain and the un-amplified spontaneous emission (ASE) coupled into the laser waveguide mode are extracted from the ASE spectrum of Fabry?PErot semiconductor lasers by the Fourier transform method with a ... -
Determination of the PIn antisite structure in InP by optically detected electron-nuclear double resonance
DONEGAN, JOHN FRANCIS (American Physical Society, 1987)Optically detected electron-nuclear double resonance (ODENDOR) is reported for the PIn antisite in p-type InP. In both electron-irradiated and as-grown samples, ENDOR signals from the four nearest P neighbors and the next ... -
Device design of 1.3?m AlGaInAs-InP narrow strip structure for self-pulsation operation
DONEGAN, JOHN FRANCIS (SPIE, 2005)A complete design of 1.3 ?m AlGaInAs/InP narrow stripe semiconductor lasers for self-pulsating operation is realised by using a 2?1D simulation model. This numerical model is based on the effective index method and ... -
Direct measurement of exchange as a function of separation for discrete donor-acceptor pairs in ZnSe
DONEGAN, JOHN FRANCIS (American Physical Society, 1988)We describe optical detection of magnetic resonance for 17 well-resolved discrete zinc interstitial donor-zinc vacancy acceptor pairs of varying separation in ZnSe. For most of the pairs, microwave transitions are detected ... -
Effect of Coulomb enhancement on optical gain in (Zn,Cd)Se/ZnSe multiple quantum wells
DONEGAN, JOHN FRANCIS; HEGARTY, JOHN (American Physical Society, 1997)The optical-gain spectra of a 40-? (Zn,Cd)Se/ZnSe multiple quantum well has been measured at various temperatures using a variable-stripe method. By comparison with a gain calculation including many-body effects, we have ... -
Effect of ZnS Shell Thickness on the Phonon Spectra in CdSe Quantum Dots
DONEGAN, JOHN FRANCIS; RAKOVICH, YURY; MOORE, ALAN; PEROVA, TANIA (The American Physical Society, 2003)The evolution of the optical phonon spectra of colloidal core/shell CdSe/ZnS quantum dots with an increase of the shell thickness from 0.5 to 3.4 monolayers has been studied by resonant Raman spectroscopy. The results ... -
Electron paramagnetic resonance and photoluminescence study of Er-impurity complexes in Si
BARKLIE, ROBERT CHARLES; DONEGAN, JOHN FRANCIS (American Physical Society, 1999)Electron paramagnetic resonance (EPR) and photoluminescence (PL) spectroscopy have been used to examine the structure and optical properties of erbium-impurity complexes formed in float-zone Si by multiple-energy implants ... -
Electron paramagnetic resonance of erbium doped silicon
DONEGAN, JOHN FRANCIS; BARKLIE, ROBERT CHARLES (American Institute of Physcis, 1996)Electron paramagnetic resonance measurements have been made on samples of float zone silicon, implanted with 1015 Er/cm2. One sample was coimplanted with oxygen to give an impurity concentration of 1020 O/cm3 and 1019 ... -
Engineering the exciton linewidth in II-VI quantum well structures
DONEGAN, JOHN FRANCIS; HEGARTY, JOHN (SPIE, 1994)The excitonic transition in Il-VI quantum well materials has recently been used as the basis for optical modulators and also as the lasing transition at low temperatures. The central aspect in the use of the exciton ... -
Enhancement of quality factor for TE whispering-gallery modes in microcylinder resonators
GUO, WEI-HUA; LU, QIAOYIN; DONEGAN, JOHN FRANCIS (2010)The enhancement of quality factor for TE whispering-gallery modes is analyzed for three-dimensional microcylinder resonators based on the destructive interference between vertical leakage modes. In the microcylinder ... -
Measuring the lateral size of liquid-exfoliated nanosheets with dynamic light scattering
COLEMAN, JONATHAN NESBIT; DONEGAN, JOHN FRANCIS (2013)We have developed an in-situ method to estimate the lateral size of exfoliated nanosheets dispersed in a liquid. Using standard liquid exfoliation and size-selection techniques, we prepared a range of dispersions of graphene, ... -
Metal surface enhanced emission from CdTe quantum dots
BRADLEY, LOUISE; DONEGAN, JOHN FRANCIS; RAKOVICH, YURY (IEEE, 2005)In this paper the enhancement in emission from CdTe quantum dots (QDs) on Au island film as a function of CdTe-Au distance is reported. The observed enhancement can be partially explained by increased absorption cross ... -
Microtube cavities from templated filtering: confined optical modes and amplified spontaneous emission
MOORE, ALAN; GOUNKO, IOURI; DONEGAN, JOHN FRANCIS; PEROVA, TANIA; RAKOVICH, YURY (American Institute of Physics, 2006)The authors demonstrate a new route to the fabrication of individual aluminosilicate microtubes that can act as micron-scale optical cylindrical resonators. The microtubes were prepared using a simple vacuum assisted ... -
Microwave-assisted synthesis of icosahedral nickel nanocrystals
HOLMES, JUSTIN DEREK; DONEGAN, JOHN FRANCIS (2011)Nickel nanocrystals with icosahedral morphologies have been successfully synthesised using a microwave-assisted irradiation method. Nickel acetylacetonate was used as the metal precursor, while sodium formate and ... -
Multi-species gas sensing using monolithic widely tuneable laser diodes
DONEGAN, JOHN FRANCIS (SPIE, 2005)Widely tuneable laser diodes operating in the 1520 ? ? ? 1570 nm are characterised and compared for use as sources for tuneable laser diode gas absorption spectroscopy. Three gases hydrogen cyanide, ammonia and acetylene ... -
Observation of nonradiative energy transfer in the excitation of Nd3+ in GaP
DONEGAN, JOHN FRANCIS (American Physical Society, 1990)We have carried out luminescence-excitation measurements on a Nd3+ complex in GaP in the range 1.5?2.2 eV to determine the mechanisms by which the internal Nd3+ luminescence is generated. At low temperatures we observe ...