Abstract

We have made what we believe to be the first observation of two-photon absorption in Cr-phthalocyanine. The wavelenth dependence is consistent with the two-photon excitations to B_g energy levels calculated by Ho et al.(1)The strength of acoustic grating formed by intersecting 30 ps pulses in 2microns thick polycarbonate film doped with 3×10⁻⁴ mol per gram of polymer Cr-phthalocyanine was monitored by Bragg scattering of a delayed pulse from acoustic pattern. The scattered signal intensity varied as the square of intensities of intersecting 1.06 micron pulses in the range of 0.5 to 2.4 GW/cm² . The scattered signal was unobservable and at least lowered by factor of 10⁻² at the other wavelength studied: 0.532, and 0.59-0.62 micron. This is consistent with the existence of two-photon excitable levels estimated to be near 20,000 cm⁻¹ by Ho, et al.(1) No two-photon transition would be expected at the other wavelengths we used based on energy levels estimated by them.

© 1989 Optical Society of America