Coherent quantum control of two-photon absorption and polymerization by shaped ultrashort laser pulses

The polymerization and feature size in micro/nanofabrication are usually controlled by changing the femtosecond laser pulse energy and irradiation pulse number. In this paper, we present the coherent control of two-photon absorption (TPA) and polymerization in a polymer with a isopropyl thioxanthone (ITX) photoinitiator by modulating the phase of 800 nm femtosecond laser pulses. We demonstrate experimentally and theoretically that the TPA probability and polymerization can be efficiently controlled by shaped ultrashort laser pulses. By using this method, the volume of a fabricated microrod decreases to 1/125 of that induced by Fourier transform limit laser pulses, and it is less than 1/25 of the diffraction limit.