Frequency-stabilized cavity ring-down spectroscopy

► High precision cw-cavity ring-down spectrometer with stabilized frequency axis. ► Ultrastable, linear frequency axis with precisions down to 12 kHz. ► Stable, single mode operation gives minimum detectable absorption coefficient of 1.8 × 10−11 cm−1. ► Precise measurements of line parameters of O2, CO2 and H2O for remote sensing. ► Enhancements should give SNR > 200 000:1 and frequency uncertainties near 10 kHz.