High speed cavity ringdown spectroscopy with increased spectral resolution by synchronous laser and cavity tuning

Non-intrusive optical sensing tools are needed to monitor trace molecular oxygen (O/sub 2/) in reactive flows generated in blow-down wind tunnels. Continuous-wave cavity ringdown spectroscopy (cw-CRDS) is a promising candidate to perform such analysis. However, those measurements impose strong constraints since flow generation is realized during short gusts (200 ms), characterized by low pressures and aerodynamic conditions changing rapidly. The crucial issue therefore consists in developing CRDS as a fast and high-resolution diagnostic method.