N.M. Bojanowski, A. Vranic, V. Hahn, P. Rietz, T. Messer, J. Brückel, C. Barner-Kowollik, E. Blasco, S. Bräse, and M. Wegener

Adv. Funct. Mater. 2212482 (2022)

Abstract:

Recent studies have opened the door to a new generation of photoinitiators for 3D laser nanoprinting. Therein, the simultaneous absorption of two photons, commonly referred to as two-photon absorption, is replaced by the sequential absorption of two photons in two consecutive one-photon absorption processes. This process has been termed two-step absorption. Importantly, two-step absorption can be accomplished by inexpensive compact low-power continuous-wave blue laser diodes instead of femtosecond laser systems in the red spectral region. Red-shifting the second absorption step with respect to the first one results in an and-type optical nonlinearity based on two-color two-step absorption. Herein, alternatives are systematically explored to the few already reported one- and two-color two-step-absorption photoinitiators, including the search for photoinitiators that can be excited by one-color two-step absorption and be de-excited by a disparate laser color.