Abstract
Using high repitition rate femtosecond pump-probe techniques we examine the thermalization of carriers injected a few LO phonon energies above the band in a CdS0.24Se0.76 microcrystallite doped glass. The ouput of a balanced CPM ring dye laser is amplified with a copper vapor laser at 7.3 kHz to 2-μJ energy and 200-fs duration. A fraction of the amplified pulse at 6200 Å is used as a pump pulse while the remainder is focused to 1013 W cm-2 on an ethylene glycol jet producing a broad-bandwidth probe pulse. For various pump-probe delays the transmission of a 750-μm thick sample is measured. As shown in fig 1a., a red shift of the absorption edge is observed in < 100 fs at wavelengths in the vicinity of the band gap. This is due to the combined effects of band gap renormalization and tail state broadening. After +300 fs a prominent shift of the absorption edge toward higher energies is observed. This suggests that carriers have relaxed to the bottom of the band in a few hundred femtoseconds and initiated bandfilling. The blue shift of the absorption spectrum is in agreement with a steady state measurement reported previously.1 Finally, after a few picoseconds the band-edge shift begins to recover via electron-hole recombination with nearly complete recovery after +40 ps. We observe a small residual shift which persists for > 500 ps, attributed to carriers confined to traps.
© 1986 Optical Society of America
PDF ArticleMore Like This
Greg R. Olbright, B. D. Fluegel, and N. Peyghambarian
THB5 OSA Annual Meeting (FIO) 1986
M.C. Nuss, W. Zinth, and W. Kaiser
ME2 International Conference on Ultrafast Phenomena (UP) 1986
M. C. NUSS, W. ZINTH, and W. KAISER
MBB2 International Quantum Electronics Conference (IQEC) 1986