Abstract

Ultrafast optical dephasing measurements were performed on thin films of the oxazine dye Nile Blue in poly- [vinyl alcohol] (PVOH). The experimental technique used two-beam, time-delayed degenerate four-wave mixing (DFWM) with incoherent light.¹⁻³ Small time delay oscillations in the DFWM signal were observed under the conditions that the sample was at relatively high temperatures (between 200° K and room temperature) and the measurements were made on the blue side of the Nile Blue inhomogeneous distribution. These conditions are consistent with relatively fast dephasing times.² A comparison between the measured oscillation depth and a numerical simulation of the DFWM scattered intensity yields an estimate of the phase relaxation time. This technique offers a new method of measuring femtosecond dephasing times with applications to samples of broad homogeneous linewidths, at high temperatures or in highly interacting environments.

© 1998 Optical Society of America