Ring-down binning in FSR hopping mode

摘要

For cavity enhanced optical spectroscopy, the cavity modes are used as a frequency reference. Data analysis methods are employed that assume the data points are at equally spaced frequencies. Parameters of interest such as line width, integrated absorption etc. can be determined from such data without knowledge of the frequencies of any of the data points. Methods for determining the FSR index of each ring-down event are also provided.

主权项

1. A method for performing cavity enhanced optical spectroscopy, the method comprising:
providing an optical resonator that defines a first set of cavity modes having a free spectral range (FSR) and which is configured to include a sample for analysis, wherein the optical resonator is configured to passively provide relative frequency stability of the first set of cavity modes of 10% or less of the FSR in a time period of about 1 second; providing an optical source configured to deliver optical radiation to the optical resonator; providing a detector configured to receive an absorbance signal from the optical resonator that is responsive to optical absorption in the sample; collecting spectrograms from the sample by sweeping a frequency of the optical source through two or more frequencies of the first set of cavity modes and recording the absorbance signal; computing an analysis output from the spectrogram by assuming that data points in the spectrogram are evenly spaced in frequency; and providing an FSR calibration between one or more optical source parameters and an FSR index.