Active control of the Pound-Drever-Hall error signal offset in high-repetition-rate cavity ring-down spectroscopy

摘要

A new approach to realizing the Pound-Drever-Hall (PDH) error signal offset correction is presented. The proposed setup and correction procedure allow one to control not only the effect of amplitude modulation of the error signal, but also other sources of offsets that are present in the PDH feedback loop. This technique significantly improves laser frequency locking in high-repetition-rate cavity ring-down spectroscopy (CRDS) by allowing one to recover a tight PDH lock within 1 ms after switching off the probe laser beam. We apply the PDH error signal offset correction to CRDS measurements of the weak ~(16)O_(2) B-band R7 Q8 line. The resulting spectra taken at a pressure of 1.2 kPa had a signal-to-noise ratio of approx8000:1.