Search for Alternative Two‐Step‐Absorption Photoinitiators for 3D Laser Nanoprinting
N. Maximilian Bojanowski, Aleksandra Vranic, Vincent Hahn, Pascal Rietz, Tobias Messer, Julian Brückel, Christopher Barner‐Kowollik, Eva Blasco, Stefan Bräse, Martin Wegener
Abstract
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.