Nanophotonic supercontinuum-based mid-infrared dual-comb spectroscopy
Hairun Guo, Wenle Weng, Junqiu Liu, Fan Yang, Wolfgang Hänsel, Camille Sophie Brès, Luc Thévenaz, Ronald Holzwarth, Tobias J. Kippenberg
Abstract
High resolution and fast detection of molecular vibrational absorption is important for organic synthesis, pharmaceutical processes, and environmental monitoring, and is enabled by mid-infrared (mid-IR) laser frequency combs via dual-comb spectroscopy. Here, we demonstrate a novel and highly simplified approach to broadband mid-IR dual-comb spectroscopy via supercontinuum generation, achieved using unprecedented nanophotonic dispersion engineering that allows for ultra-broadband and flat-envelope mid-IR frequency combs. Our mid-IR dual-comb spectrometer has an instantaneous bandwidth covering the functional group region from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mn>2800</mml:mn> </mml:math> – <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mn>3600</mml:mn> <mml:mspace width="thickmathspace"/> <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:mrow class="MJX-TeXAtom-ORD"> <mml:mo>−</mml:mo> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>1</mml:mn> </mml:mrow> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> , comprising more than 100,000 comb lines, enabling parallel gas-phase detection with a high sensitivity, sub-Doppler spectral resolution, and a high speed. In addition to the traditional functional groups, their isotopologues are also resolved in this supercontinuum-based dual-comb spectroscopy. Our approach combines well established fiber laser combs, digital coherent data averaging, and integrated nonlinear photonics, each in itself a state-of-the-art technology, signaling the emergence of mid-IR dual-comb spectroscopy for use outside of the protected laboratory environment.