Femtosecond laser-induced damage threshold of nematic liquid crystals at 1030  nm

The laser-induced damage threshold (LIDT) of nematic liquid crystals is investigated in the femtosecond regime at ≃ 1030 n m . The thickness and breakdown of freely suspended thin films ( ≃ 100 n m ) of different mixtures (MLC2073, MLC2132, and E7) is monitored in real time by spectral-domain interferometry. The duration of laser pulses was varied from 180 fs to 1.8 ps for repetition rates ranging from single shot to 1 MHz. The dependence of the LIDT with pulse duration suggests a damage mechanism dominated by ionization mechanisms at low repetition rate and by linear absorption at high repetition rate. In the single-shot regime, LIDTs exceeding 1 J / c m 2 are found for the three investigated mixtures. The LIDT of polyvinyl alcohol is also investigated by the same method.