Details of Grant 

EPSRC Reference:	GR/R74161/01
Title:	Two colour investigations of coherent and correlated processes in low dimensional semiconductor structures with FELIX
Principal Investigator:	Pidgeon, Professor C
Other Investigators:	Galbraith, Professor I
Researcher Co-Investigators:
Project Partners:
Department:	Sch of Engineering and Physical Science
Organisation:	Heriot-Watt University
Scheme:	Standard Research (Pre-FEC)
Starts:	01 January 2002	Ends:	30 June 2005	Value (£):	157,323
EPSRC Research Topic Classifications:	Materials Characterisation
EPSRC Industrial Sector Classifications:	Electronics
Related Grants:	GR/R74178/01
Panel History:
Summary on Grant Application Form
Describe the proposed research in about 200 words.Pump-probe spectroscopy has long been a powerful tool in semiconductor investigations, but is usually performed using two pulses of similar wavelgength. The recent addition of a synchronised near-IR laser system at the Dutch free electron laser facility (FELIX) provides a unique opportunity to perform new pump-probe investigations with widely different wavelengths in each pulse. We shall excite quantum wells with intense THz pulses, and measure the reflectivity spectrum of the interband pulses as a function of phase, intensity, THz frequency and applied magnetic field. This spectrum will be interpreted with the (magneto-) excitonic dynamical Franz-Keldysh effect. The same system will resonantly pump electrons from the ground state to the first excited subband in doped quantum wells. Using the interband probe we shall measure the transmission spectrum as a function of time and thus obtain the temporal k-space occupation. This will allow direct measurement of both intersubband and intrasubband electon-electron scattering. Using instead the interband pulse as the pump and the intraband (THz) pulse as the probe, we propose to measure the excited 1 s-2p transition energy spectrum as a function of resonant and nonresonant interband excitation and time. This will enable us to determine the mechanism by which excitons form and whether they are geminate. Finally the THz transient generation system at Surrey will be used for complementary experiments, specifically to perform interband pump-THz probe measurement of the lifetime of coherent collective intraband excitations.
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Organisation Website:	http://www.hw.ac.uk