Abstract

We report a new technique for probing femtosecond dephasing processes in solids, requiring only low excitation intensities. The method is based on measurement of the spontaneous emission spectrum of a thin sample (~2 μm) in front of a mirror, excited by 40-fs pulses from a colliding pulse mode- locked (CPM) laser. Figure 1(A) shows the simplified level scheme of a prototype molecule, and Fig. 1(B) gives the schematics of the experimental arrangement. The presence of a mirror has two effects. First, it leads to the creation of a transient Wiener fringe pattern¹; second, it leads to an interference effect in spontaneous emission.

© 1990 Optical Society of America