Investigation of transient nonlinear optical mechanisms using a variable pulselength laser

We show a variable pulselength laser to be extremely useful when investigat ing the dynamics and parameters of optomechanical nonlinarities in optical materials. Pulselength variability allows observation of the transient nonl inear behavior using nanosecond pulses and determination of the underlying physical mechanisms using subnanosecond pulses. It also enables observation elf the transition response between the two time regimes where intrinsic p olarizabilities compete with optomechanical effects. We examine the transie nt nonlinear scattering properties of an optical power limiter, platinum et hynyl, and compare it to carbon disulfide using degenerate four-wave mixing . Intensity, polarization, and pulselength control allow us to measure acou stic scattering and decay parameters, chi((3)) magnitudes, and the transien t laser-induced grating behavior.