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230 results on '"Houlihan J"'

9. Ultrafast gain and refractive index dynamics in GaInNAsSb semiconductor optical amplifiers.

Author

Piwonski, T., Pulka, J., Madden, G., Huyet, G., Houlihan, J., Pozo, J., Vogiatzis, N., Ivanov, P., Rorison, J. M., Barrios, P. J., and Gupta, J. A.

Subjects
OPTICAL amplifiers, SEMICONDUCTORS, ABSORPTION, LIGHT amplifiers, STATICS, SOLID state electronics
Abstract

The gain and refractive index dynamics of dilute nitride antimonide semiconductor optical amplifiers are studied using heterodyne pump probe spectroscopy, both in forward and reverse bias regimes. In the forward biased absorption regime, both gain and refractive index relax on the same timescale indicating that both quantities are linked to the same relaxation process, interband recombination. Above transparency, in the forward biased gain regime, the gain and phase exhibit differing timescales resulting in a dynamical alpha factor that varies strongly with time. Reversed bias measurements suggest a recombination dominated absorption recovery where the recovery timescale increases with increasing reversed bias, possibly due to charge separation effects. [ABSTRACT FROM AUTHOR]

Published
2009
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13. Interconnection between ground state and excited state gain in InAs/GaAs quantum dot semiconductor optical amplifiers

Author

Crowley, M. T., Andreev, A. D., Piwonski, T., Houlihan, J., O'Reilly, E. P., and Huyet, G.

Subjects
Optics Research Group
Abstract

Different energy levels are generally assumed to be associated with ground state (GS) and excited state (ES) gain in semiconductor qunatum dot lasers and amplifiers. We present calculations based on 8 band k.p Hamiltonian which show that this is not the case. Two distinct absorption bands are calculated due to transitions between the GS electrons and all dot hole states. In additon to the peak due to transitions between GS electron and GS hole levels, a higher energy band is also calculated due ot transistions between GS electrons and highly excited dot hole states. We demonstrate that the removal of electron-hole pairs through simulated emission at the ES gain maximum can result in an amplitude reduction for a probe pulse tuned to the GS gain maximum, due to the existence of these higher energy transitions, and also due to the effects of two photon absorption. We also find that the instatneous phase change at the ES gain maximum due to dot to dot interband transistions is small compared to the measured value. (c) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Published
2009

14. Electron and Hole Dynamics of InAs∕GaAsInAs∕GaAs Quantum Dot Semiconductor Optical Amplifiers

Author

O'Driscoll, I., Piwonski, T., Schleussner, C. F., Houlihan, J., Huyet, G., and Manning, R. J.

Subjects
Physics, scattering, article, chemical reactions, quantum dots, tyndall institute of photonics, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, openaire, pdf, 1.3 PHYSICAL SCIENCES, equilibrium thermodynamics, amplified spontaneous emission, Condensed Matter::Materials Science, department of physical sciences, quantum wells, electronic transport, optical coatings, Physical Sciences and Mathematics, electron capture, semiconductor optical amplifiers
Abstract

Single-color and two-color pump-probe measurements are used to analyze carrier dynamics in InAs∕GaAs quantum dot amplifiers. The study reveals that hole recovery and intradot electron relaxation occur on a picosecond time scale, while the electron capture time is on the order of 10ps. A longer time scale of hundreds of picoseconds is associated with carrier recovery in the wetting layer, similar to that observed in quantum well semiconductor amplifiers.

Published
2007

21. Experimental investigation of a bistable system in the presence of noise and delay

Author

Universitat Politècnica de Catalunya. Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya. DONLL - Dinàmica no Lineal, Òptica no Lineal i Làsers, Houlihan, J., Goulding, D., Busch, T., Masoller Alonso, Cristina, Huyet, G., Universitat Politècnica de Catalunya. Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya. DONLL - Dinàmica no Lineal, Òptica no Lineal i Làsers, Houlihan, J., Goulding, D., Busch, T., Masoller Alonso, Cristina, and Huyet, G.

Abstract

We experimentally analyze the behavior of a non-Markovian bistable system with noise, using a vertical cavity surface emitting laser with time-delayed optoelectronic feedback. The effects of the delayed feedback are observed in the probability distribution of the residence times of the two orthogonal polarization states, and in the polarization-resolved power spectrum. They agree well with recent theoretical predictions based on a two-state model with transition rates depending on an earlier state of the system. We also observe experimentally and explain theoretically that the residence time probability distribution deviates from exponential decay for residence times close to (and smaller than) the delay time., Peer Reviewed, Postprint (published version)

Published
2004

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