Abstract

The transition metal poly-ynes, such as [Pt(PBu₃)₂C₂C₆H₄C₂]_n, have been shown to have high nonlinear optical susceptibilities according to the results of four-wave-mixing studies.¹ The fact that these materials also have low absorption in the visible (above 500 nm) and the near IR makes them interesting for many applications. Our direct measurement of two-photon absorption coefficients β of these materials gave high β values, ranging from 5 × 10^–48 to 20 × 10^–48 cm⁴s/ molecule/photon. Strong backscattering of light from solutions of the poly-ynes was also observed. Optical power-limiting studies, which employed nanosecond laser pulses, showed the solutions to be very efficient power limiters. The backscattering of light was the dominant mechanism contributing to the power limiting. The nonlinear refractive indices n₂ of the poly-ynes were measured at 532 and 1064 nm by the external self-action method using picosecond radiation. The n₂ values typically were more than 10 times that of CS₂. The large n₂ may be originating from a reorientational effect, arising from the long cylindrical structure of the molecules. Results of a study of the response time of the nonlinearity now in progress are reported.

© 1988 Optical Society of America