Intracavity trace molecular detection with a broadband mid-IR frequency comb source

Abstract

Ultrasensitive detection of methane, isotopic carbon dioxide, carbon monoxide, formaldehyde, acetylene and ethylene is performed in the spectral range 2.5 - 5 μm using intracavity spectroscopy in broadband optical parametric oscillators (OPOs). The OPOs were operated near degeneracy and synchronously pumped either by a mode-locked erbium (1560 nm) or thulium (2050 nm) fiber laser. A large instantaneous bandwidth of up to 800 cm${}^{-1}$ allows for simultaneous detection of several gases. We observe an effective path length enhancement due to coherent interaction inside the OPO cavity and achieve part-per-billion sensitivity levels. The measured spectral shapes are in good agreement with a model that takes into account group delay dispersion across the broad OPO frequency band.

25 pages, 17 figures

References in corpus (6)

• Mid-Infrared Frequency Comb Fourier Transform Spectrometer
• Quantum-noise-limited optical frequency comb spectroscopy
• Cavity-enhanced optical frequency comb spectroscopy in the mid-infrared - application to trace detection of H2O2
• Cavity-enhanced direct frequency comb spectroscopy
• Sensitive multiplex spectroscopy in the molecular fingerprint 2.4 $\mu$m region with a Cr^{2+}:ZnSe femtosecond laser
• Soliton absorption spectroscopy

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• Massively parallel dual-comb molecular detection with subharmonic optical parametric oscillators