Description:
<jats:p>The laser-induced damage threshold (LIDT) of nematic liquid crystals is
investigated in the femtosecond regime at <jats:inline-formula>
<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>
</jats:inline-formula>. The thickness and breakdown of
freely suspended thin films (<jats:inline-formula>
<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>
</jats:inline-formula>) 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 <jats:inline-formula>
<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>
</jats:inline-formula> are found for the three investigated
mixtures. The LIDT of polyvinyl alcohol is also investigated by the
same method.</jats:p>