Two-octave-wide (3–12 µm) subharmonic produced in a minimally dispersive optical parametric oscillator cavity
Qitian Ru, Taiki Kawamori, Peter G. Schunemann, Sergey Vasilyev, Sergey Mirov, Konstantin L. Vodopyanov
Abstract
We report a subharmonic (frequency-divide-by-2) optical parametric oscillator (OPO) with a continuous wavelength span of 3 to 12 µm ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>−</mml:mo> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>37</mml:mn> </mml:mrow> <mml:mspace width="thickmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">d</mml:mi> <mml:mi mathvariant="normal">B</mml:mi> </mml:mrow> </mml:math> level) that covers most of the molecular rovibrational “signature” region. The key to obtaining such a wide spectral span is the use of an OPO with a minimal dispersion—through the choice of intracavity elements, the use of all gold-coated mirrors, and a special “injector” mirror. The system delivers up to 245 mW of the average power with the conversion efficiency exceeding 20% from a 2.35 µm Kerr-lens mode-locked pump laser.