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 poly(vinyl-butyral) 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 can be analysed as having contributions from in-plane distortions of the chromophore that remove its nominal four-fold symmetry and thus the degeneracy of the Q band. Other contributions, perhaps associated with axial ligation of the chromophore, remove the plane of symmetry and contribute differently to the broadened profile.