Pulse propagation experiments are performed with coherent picosecond laser pulses in resonance with the donor bound A-exciton (I<sub>2</sub>) state in CdS. Using bandwidth-limited time-resolved spectroscopy, we investigate the intensity of the transmitted laser pulse as a function of monochromator energy position and time. This method permits the determination of both the amplitude and the phase of the complex electricfield amplitude. Studying the dependence of pulse propagation on the input intensity, for small-area pulses we found at the rear of the sample the spectral hole formation and beating characteristic of a 0π pulse. At large pulse areas close to 2π the pulse propagates nearly unperturbed, showing no oscillatory reshaping or significant absorption losses. This provides clear evidence for self-induced transparency at an excitonic state in solids. Our interpretation is substantiated by an analysis within the framework of the combined Maxwell and optical Bloch equations.
© 1996 Optical Society of AmericaPDF Article