Doppler-free two-photon cavity ring-down spectroscopy of a nitrous oxide (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi mathvariant="normal">N</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi mathvariant="normal">O</mml:mi></mml:mrow></mml:math>) vibrational overtone transition
Gang Zhao, D. Michelle Bailey, Adam J. Fleisher, Joseph Hodges, Kevin K. Lehmann
Abstract
We report Doppler-free two-photon absorption of ${\mathrm{N}}_{2}\mathrm{O}$ at $\ensuremath{\lambda}=4.53\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{m}$, measured by cavity ring-down spectroscopy. High power was achieved by optical self-locking of a quantum cascade laser to a linear resonator of finesse $\mathcal{F}=22730$, and accurate laser detuning over a 400-MHz range was measured relative to an optical frequency comb. At a sample pressure of $p=0.13\phantom{\rule{0.16em}{0ex}}\mathrm{kPa}$, we report a large two-photon cross section per molecule of ${\ensuremath{\sigma}}_{13}^{(2)}=8.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}41}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{4}\phantom{\rule{0.16em}{0ex}}\mathrm{s}$ for the $Q(18)$ rovibrational transition at a resonant frequency of ${\ensuremath{\nu}}_{0}=66179400.8\phantom{\rule{0.16em}{0ex}}\mathrm{MHz}$.