Electric-field-induced broadening of spectral holes in zinc phthalocyanine

The influence of an externally applied electric field on spectral holes burnt into the Q band of zinc phthalocyanine doped into polymethylmethacrylate has been investigated. The changes in hole shape as a function of electric field have been monitored and a linear Stark effect has been observed. The broadening has a strong dependence on the direction of polarisation of the burning and reading laser relative to the applied electric field. This dependence on polarisation indicates that not only is there a dipole induced in the plane of the chromophore by the host, but also that there are strong interactions with the chromophore perpendicular to the molecular plane. The magnitude of the Stark broadening depends strongly on the presence or absence of solvent in the sample.