Investigation of parameters governing damage resistance of nematic liquid crystals for high-power or peak-intensity laser applications

Abstract

We investigate the damage resistance of saturated and unsaturated liquid crystals (LC’s) under a wide range of laser excitation conditions, including 1053-nm pulse durations between 600 fs and 1.5 ns and nanosecond pulse excitation at 351 nm and 532 nm. This study explores the relationship between the LC’s resistance to laser-induced breakdown (damage) and the electronic structure (π-electron delocalization) of the constituent molecules. The laser-induced damage threshold at all wavelengths and pulse durations was consistently higher in saturated materials than in their unsaturated counterparts. The wavelength’s dependence in the results suggests that the energy coupling process that leads to laser-induced breakdown is governed by the energy separation between the ground state and the first and second excited states, while the pulse duration’s dependence in the results reveals the important role of electron relaxation between the excited states. A qualitative description was developed to interpret the experimental observations.

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

“…Furthermore, it is found that LIDT for MLC2132 is nearly identical, while MLC2073 LIDT is 1.5 times higher. This is in good agreement with their bandgap energy ratio (Table I) and, following [19], it confirms that mixtures with higher bandgap present higher resistance to laser damage for single-shot exposure. Besides, MLC2132 has a more deterministic behavior than the two other mixtures, which is not understood at this stage.…”

“…We underline that our measurements nicely complete the study reported in [19], in which the minimum laser pulse duration was 600 fs. Values reported for E7, the common mixture to both studies, are in overall good agreement.…”

“…In contrast, at high repetition rate, the breakdown seems dominated by thermal accumulation induced by a residual linear absorption. In both cases, these values complete the formerly reported study [19] and strengthen applications of nematics to intense and/or ultrashort light shaping.…”

“…Thus, PVA is not a critical issue for most of LCbased laser shapers. However, for mixtures with higher LIDT (saturated compounds or glassy LC mixtures [19]), alternative anchoring techniques [34] might be preferred . LIDT results with single-shot exposure are shown in Fig.…”

“…Recently, Kosc and co-authors reported on a systematic study to determine LIDT in thick nematic cells, for pulse duration ranging from 600 fs to 1.5 ns at different laser wavelengths (351 nm, 532 nm and 1053 nm) [19]. One of the conclusion of [19] is that saturated materials (i.e. featuring a higher bandgap energy) invariably exhibit higher LIDT that unsaturated ones.…”