Exciton free induction in II-VI thin films observed by transient Brewster-angle reflectance spectroscopy
Takashi Kuroda, Kuon Inoue, Ikuo Suemune +2 more
The coherent emission process at excitonic resonance was first investigated in short-period ZnSe/ZnSxSe1-x (x equals 0.18) superlattices with one period of 50 A/50 A and 19 A/19 A by observing a temporal profile with subpicosecond time resolution, of reflected pulses in the Brewster-angle configuration. As a result, an almost background-free signal with nonresonant contribution reduced greatly, was observed reflecting free induction decay (FID) of coherently driven exciton polarization. In particular, a beat signal of FID was clearly observed for the first time, which arises from interference effect between a few split spectral lines of the relevant exciton. Further, it was confirmed that the decay spread of FID becomes faster as the power density of incident pulse was increased for the SL sample with a thicker well. The results may be explained qualitatively by a simple model with the knowledge of the exciton structure as well as a preliminary data of the phase relaxation time obtained by four- wave-mixing measurement. The present results have provided a basis for that the transient Brewster-angle reflection spectroscopy serves as a powerful tool for exploring coherent interaction of exciton with light.
Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Feb 9, 1995•1 citation