Femtosecond laser-induced damage threshold of nematic liquid crystals at 1030 nm
Loïc Ramousse, G. Chériaux, Cyrille Claudet, Aurélie Jullien
Abstract
The laser-induced damage threshold (LIDT) of nematic liquid crystals is investigated in the femtosecond regime at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mo>≃</mml:mo> <mml:mn>1030</mml:mn> <mml:mspace width="thickmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">n</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:math> . The thickness and breakdown of freely suspended thin films ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mo>≃</mml:mo> <mml:mn>100</mml:mn> <mml:mspace width="thickmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">n</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:math> ) 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mn>1</mml:mn> <mml:mspace width="thickmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">J</mml:mi> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>/</mml:mo> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">c</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msup> </mml:mrow> </mml:math> are found for the three investigated mixtures. The LIDT of polyvinyl alcohol is also investigated by the same method.