title: Grating-cavity continuous-wave optical parametric oscillators for high-resolution mid-infrared spectroscopy.
abstract: The use of grating as a spectral filter provides a simple way of improving wavelength tuning and stability of continuous-wave optical parametric oscillators (cw OPOs). In this paper, we discuss how to design and use such grating-cavity cw OPOs for high-resolution spectroscopy in the molecular fingerprint region at ∼3μm. The first design presented in the paper is based on a metal-coated diffraction grating, which produces fast and broad wavelength tuning and high wavelength stability. The second design uses a bulk Bragg grating for high optical power and good spectral purity. We report a new Bragg-grating OPO and demonstrate its use in a Doppler-free absorption spectroscopy of CH4 at ∼3.22μm. In addition, we describe a new balanced detection scheme, which can be used to improve the signal-to-noise ratio of absorption measurements if the measurement noise is limited by the intensity noise of the mid-infrared OPO.
authors.affiliation: Department of Chemistry, University of Helsinki, Helsinki, Finland.
authors.forename: Markku
authors.initials: M
authors.lastname: Vainio
authors.forename: Mikael
authors.initials: M
authors.lastname: Siltanen
authors.forename: Jari
authors.initials: J
authors.lastname: Peltola
authors.forename: Lauri
authors.initials: L
authors.lastname: Halonen