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113 results on '"Glynn, T. J."'

8. Population dynamics of the three-micron emitting level of Er3+ in YAlO3.

Author

Georgescu, S., Lupei, V., Trifan, M., Sherlock, R. J., and Glynn, T. J.

Subjects
DYNAMICS, LASERS, ERBIUM, CRYSTALS, ENERGY transfer
Abstract

Analyzes the nonexponential behavior of the kinetics of the initial laser level for three-micron generation in an erbium&sup3+;:YAlO[sub3] crystal under intense pump in the [sup4]S[sub3/2] level. Models used to explain the absence of self-saturation for three-micron room-temperature laser emission; Factor that contributes to the energy transfer to accidental impurities; Type of impurities.

Published
1996
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10. Identifications and quantitative measurements of narcotics in solid mixtures using near-IR Raman spectroscopy and multivariate analysis

Author

Alan Ryder, O Connor, G. M., Glynn, T. J., and ~|Enterprise Ireland |~

Subjects
Narcotics, Raman spectroscopy, Quantitative Analysis, Chemometrics, Forensics
Abstract

Raman spectroscopy offers the potential for the identification of illegal narcotics in seconds by inelastic scattering of light from molecular vibrations. In this study cocaine, heroin, and MDMA were analyzed using near-IR (785 nm excitation) micro-Raman spectroscopy. Narcotics were dispersed in solid dilutants of different concentrations by weight. The dilutants investigated were foodstuffs (flour, baby milk formula), sugars (glucose, lactose, maltose, mannitol), and inorganic materials (Talc powder, NaHCO3,MgSO4 .7H2O). In most cases it was possible to detect the presence of drugs at levels down to ~10% by weight. The detection sensitivity of the Raman technique was found to be dependent on a numberof factors such as the scattering cross-sections of drug and dilutant, fluorescence of matrix or drug, complexity of dilutant Raman spectrum, and spectrometer resolution. Raman spectra from a series of 20 mixtures of cocaine and glucose (0 100% by weight cocaine) were collected and analyzed using multivariate analysis methods. An accurate prediction model was generated using a Partial Least Squares (PLS) algorithm that can predict the concentration of cocaine in solid glucose from a single Raman spectrum with a root mean standard error of prediction of 2.3%. Science & Technology Against Drugs Programme (Forbairt) peer-reviewed

Published
1999

30. STEM (scanning transmission electron microscopy) analysis of femtosecond laser pulse induced damage to bulk silicon.

Author

Coyne, E., Magee, J. P., Mannion, P., O'Connor, G. M., and Glynn, T. J.

Subjects
SCANNING transmission electron microscopy, SCANNING electron microscopy, SILICON, ULTRASHORT laser pulses, STRAINS & stresses (Mechanics), PHYSICS
Abstract

This work reports on the structural changes that take place in wafer grade silicon when it is micro-machined with ultra-short laser pulses of 150 fs duration. A Chirped Pulse Amplification (CPA) Ti:Sapphire laser was used, with an operating wavelength centered on 775 nm and a maximum repetition rate of 1 KHz. The laser induced damage was characterized over the fluence range 0.43-14 J?cm-2, and for each fluence a progressively increasing number of pulses was used. The analytical tools used to characterize the samples were all based upon electron microscopy. A 30 KeV scanning transmission electron microscope (STEM) imaging technique was developed to observe defects in the crystal lattice and the thermal-mechanical damage in the area surrounding the laser machined region. Mechanical cross sectioning (in conjunction with Scanning Electron Microscope (SEM) surface imaging) was also used to reveal the internal structure, composition, and dimensions of the laser machined structures. Based on this analysis, it will be shown that laser machining of silicon with femtosecond pulses can produce features with minimal thermal damage, although lattice damage created by mechanical stresses and the deposition of ablated material both limit the extent to which this can be achieved, particularly with high aspect ratios. A key feature of the work presented here is the high-resolution STEM images of the laser-machined structures. [ABSTRACT FROM AUTHOR]

Published
2005
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33. Electrical analysis of femtosecond laser pulse absorption in silicon

Author

Coyne, E., O'Connor, G. M., and Glynn, T. J.

Abstract

We report a study of femtosecond laser pulse absorption of wafer grade silicon with an average pulse duration of 150 fs, centred on a wavelength of 775 nm. The electrical response of the laser excited carriers, over a range of fluences up to the ablation threshold for silicon is analysed. The silicon used for the experiments is a uniformly doped P-type wafer with a concentration of 1 × 1012cm−3throughout its volume. The purpose of this work is to use the electrical properties of the excited carriers as a method for analysing the interaction between femtosecond pulses and the silicon lattice below the ablation threshold, and to determine the evolution of the excited carriers after the femtosecond pulse is absorbed in silicon. This paper uses simulation software to solve the ambipolar continuity equation for the evolution of the excited carrier group given the initial values and boundary conditions of the experimental system. The paper derives results for the total number of excited carriers created as a function of laser fluence, in addition to the bulk excited carrier dynamics and lifetime after femtosecond laser excitation. Based on the results for the total number of excited carriers as a function of the average laser fluence, a value of 0.09 J cm−2is measured as the fluence where lattice defects started to reduce the effective quantity of carriers that could be detected and hence indicated incubation lattice damage.

Published
2006
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40. New Materials for Tunable Lasers in the Near Infrared

Author

Donegan, J. F., Morgan, G. P., Glynn, T. J., and Walker, G.

Abstract

There has been considerable recent effort aimed at realising tunable near-infrared laser action in solid-state media. Beyond 1 μm Ni2+ and Co2+ emissions have been mainly studied, and laser action has been achieved in several materials doped with these ions although usually only at low temperatures. Luminescence from Co2+ and Ni2+ in the host material LiGa5O8 is described and evidence is presented for a high quantum efficiency, even up to room temperature. We describe also the results of our lifetime and luminescence measurements on the various active centres in the Mg2SiO4: Cr laser system.

Published
1990
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