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Current ResearchWe research the dynamics of low-energy (~meV) physical processes in inorganic and organic systems on a femtosecond timescale. At present we are studying electronic (intersubband) processes in semiconductor nanostuctures, as well as conformational dynamics of organic semiconductors. We develop and use non-linear optical spectroscopic techniques to help us understand these systems. Time domain spectroscopy provides us with a sensitive and elegant technique for studying low-energy phenomena. In this technique short (~10fs) laser pulses are used to both generate and detect coherent pulses of mid or far-infrared light. The use of time-domain optical-pump / infrared-probe spectroscopy allows us to resolve the time evolution of optically triggered events. Single-optical-cycle pulses of mid-infrared and far-infrared (THz) light are required for our time domain spectroscopic studies. Therefore we are interested in developing more powerful and broader-band single-cycle light sources. Recently, our fundamental research on the electron dynamics and dielectric properties of photo-excited semiconductors has allowed us to develop a novel device which emits single-cycle THz pulses. Intersubband semiconductor devices such as quantum-well infrared photodetectors, quantum cascade lasers and resonant tunnelling diodes show promise for applications in high-speed communications and novel electronic devices. This is primarily because of the ultrafast electronic transition rates in these devices. We are studying the dynamics of electrons in these structures with the aim of designing future intersubband devices. 
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Current Research Support
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