Terahertz gas phase spectroscopy using a high finesse Fabry-Pérot cavity

Francis Hindle (1) , Robin Bocquet (1) , Anastasiia Pienkina , Arnaud Cuisset (1) , Gaël Mouret (1)

1 LPCA - Laboratoire de Physico-Chimie de l'Atmosphère

The achievable instrument sensitivity is a critical parameter for the continued development of THz applications. Techniques such as Cavity-Enhanced Techniques and Cavity Ring Down Spectroscopy have not yet been employed at THz frequency due to the difficulties to construct a high finesse Fabry-P\'erot cavity. Here, we describe such a THz resonator based on a low-loss oversized corrugated waveguide with highly reflective photonic mirrors obtaining a finesse above 3000 around 620 GHz. These components enable a Fabry-Perot THz Absorption Spectrometer with an equivalent interaction length of one kilometer giving access to line intensities as low as 10-27cm- 1/(molecule/cm2) with a S/N ratio of 3. In addition, the intracavity optical power have allowed the Lamb-Dip effect to be studied with a low-power emitter, an absolute frequency accuracy better than 5 kHz can be easily obtained providing an additional solution for rotational spectroscopy.

Domaines: Physique Générale [physics.gen-ph]; Instrumentations et Détecteurs [physics.ins-det]

Francis Hindle, Robin Bocquet, Anastasiia Pienkina, Arnaud Cuisset, Gaël Mouret. Terahertz gas phase spectroscopy using a high finesse Fabry-Pérot cavity. Optica, 2019, 6 (12), pp.1449-1454. ⟨10.1364/OPTICA.6.001449⟩. ⟨hal-02188287⟩