High-resolution Doppler-free molecular spectroscopy with a continuous-wave optical parametric oscillator

Summary form only given. A new generation of continuous-wave optical parametric oscillators (OPOs) has appeared in the last few years as a coherent source that possesses an unique combination of advantages. After considerable development efforts, such OPOs can now provide powerful (10-250 mW) coherent radiation over a very wide range of infrared wavelengths (0.8-4.0 /spl mu/m), featuring extremely narrow line-width (<50 kHz), continuous tunability (several GHz), and good long-term stability (<100 MHz frequency drift per hour, <5% power drift per hour) (Schneider et al, 1997; Stro/spl szlig/ner et al, 1999; Weise et al, 2000). A particularly valuable feature of the CW OPOs is that their tuning range covers the mid-infrared region around 3 /spl mu/m where fundamental vibrational modes of molecular bonds containing hydrogen occur. To demonstrate the capabilities of our new OPO design, in which we have sacrificed some of the compactness of previous OPO designs in favor of an extended cavity setup with a specially designed intracavity etalon, we have performed Doppler-free spectroscopy on methane.