Two-photon recording of stable luminescent centers in chromone-doped polymer films

The study defines threshold values of energy density required for two-photon writing of stable fluorescent bit patterns within polymer layers containing chromones class chemical compounds by visual laser pulses in range of pulse widths from nanoseconds to femtoseconds. Photo-regrouping of non-luminescent chromones to fluorescent products is shown as the result of true type two-photon absorption (TPA) and stepwise TPA as well. In the latter case writing beam fluence can be reduced due to increase of the effective TPA coefficient, but laser-induced thermal damage of matrix becomes more probable too.