Femtosecond history of free carriers in the conduction band of a wide-bandgap oxide

We present a number of methods using ultra-short laser pulses to investigate the short time behaviour of an electron gas injected in the conduction band of a wide-bandgap oxide. Electron relaxation and trapping can be observed in this way, as well as time-resolved defect creation. The achievable time resolution is at present about 10/sup -13/ s. Strong differences between apparently similar oxides are observed, which correlate with their ability to endure other types of ionising radiation. A detailed study of point defect creation in /spl alpha/-SiO/sub 2/ is presented.