Stephen A Lynch
Research interest My main interest is far-infrared (THz) laser development in impurity-doped semiconductors such as n-type silicon. There are many potential applications for new THz laser sources of radiation. These include medical diagnostics such as the early detection of skin cancer, and making our world safer by detecting bio-weapons and explosives in airports. The UK is currently a world leader in this field. I am also involved in a number of projects looking at the physics behind quantum computing in silicon. I am a regular UK user of FELIX, the free-electron laser facility in Utrecht. Here I study the relaxation dynamics of Rydberg-like impurities in silicon. These impurity levels could be used as the basis of a Qubit. My THz laser work also feeds directly into this research because it could be used in the future to optically address these Qubits in a silicon-based quantum computer. I am still active in the research field of my PhD, pulsed semiconductor laser dynamics. My most recent paper on this topic was in 2006. Some of this work has recently lead to a patent 'A self-pulsating laser diode and a method for causing a laser diode to output light pulses', which I am a co-author. Other activitiesThrough the generous funding of EPSRC I am lucky enough to be able to spend the majority of my time on full-time research. I am, however, currently attached to the Physics Department at UCL and I have some teaching duties. I am one of the staff members working in the 3rd year undergraduate laboratory and I run a number of specialised undergraduate laser experiments and mini-projects. Recent publications(A) “Intersubband electroluminescence from Si/SiGe cascade emitters at terahertz frequencies” A world first. This paper reports on the first demonstration of electroluminescence from a Si/SiGe multi-quantum well heterostructure. The paper has been cited 39 times including in a review on silicon based laser research in Science (2005). (B)“Interwell intersubband electroluminescence from Si/SiGe quantum cascade emitters”
Another world first. This paper reports on electroluminescence from a Si/SiGe true cascade superlattice structure. (C) “Towards Silicon-Based Lasers for Terahertz Sources” This paper describes current progress in silicon-based THz lasers. It contains discussions on SiGe quantum cascades and some silicon impurity work. (D) “Temperature dependence of terahertz optical transitions from boron and phosphoros dopant impurities in silicon” This paper describes the temperature dependence of electroluminescent THz transitions in n-doped silicon. (E) ““Self-Pulsation Dynamics in Narrow Stripe Semiconductor Lasers”P. Landais, S.A. Lynch, J. O’Gorman, I. Fischer, and W. Elsäßer IEEE J. Quantum Electron. Vol. 42(4), pp. 381-387, April 2006 [PDF File] A paper describing some of the physics behind self-pulsating semiconductor lasers. These lasers are commonly used in data storage devices such CD and DVD players. There are a host of new applications emerging for these interesting laser diodes. Biography • Awarded EPSRC Advanced Research Fellowship at the LCN summer 2007 Research
“Towards a Silicon Quantum Computer”: This image shows how a future silicon-impurity based quantum computer might work. The silicon substrate is implanted with both phosphorus (green) and bismuth atoms (red). The Qubit is formed from pairs of neighbouring bismuth atoms and a close-by phosphorus control atom. The spins of the bismuth atoms are then initialised (red arrows). Illumination with THz laser light of different wavelengths changes the quantum entanglement between the neighbouring bismuth pairs via the phosphorus control atom. |
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