Abstract

Liquid dynamics and optical multi-wave mixing processes form two well established areas of research that are currently attracting much interest — both theoretically and experimentally. In this paper we draw together these two subjects and describe our recent work in the laboratory and our theoretical interpretation of the results so far obtained. We describe a phase-conjugated six-wave mixing technique and present results obtained from samples comprising thin liquid films of donor-acceptor substituted stilbene dyes. Our experiment utilises a pump-probe arrangement in which a transient anisotropic grating is created within the sample and then probed after a variable time delay by recording the second-harmonic radiation generated from the grating. The arrangement used follows that of the earlier work of Fiorini et al¹ but our experiment is performed using a femtosecond Ti:Sapphire laser which gives us a temporal resolution of the order of 100 fs. This has allowed us to observe for the first time using this multi-wave mixing process the ultrafast dynamics of liquid reorientation, Fig. 1.

© 1998 IEEE