Fringe pattern suppression in intracavity laser spectroscopy

Absorption spectra obtained by intracavity laser spectroscopy (ILS) often contain fringe patterns that significantly mask absorption features and hamper the quantitative analysis of ILS data. Both the parasitic etalon fringes and the fringes that originate from spatially localized losses can be suppressed by a low-amplitude audio-frequency vibration of a folding mirror in the laser cavity. Using this methodology, we show that ILS spectra recorded with multimode lasers that contain nonideal intracavity surfaces have essentially no fringe contamination. The elimination of fringe contamination improves the detection sensitivity of ILS under normal experimental conditions and thus expands the potential for ILS applications.