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Updated: Jun 13, 2026

Characterizing Far-infrared Laser Emissions and the Measurement of Their Frequencies
Published on: December 18, 2015
Time-domain spectroscopy of molecular free-induction decay in the infrared
Ian Coddington1, William C Swann, Nathan R Newbury
1National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305, USA. ian@boulder.nist.gov
Abstract:
Time-domain spectroscopy using dual, coherent frequency combs is used to measure free-induction decay from a molecular gas sample in the near-IR with a time-domain signal-to-noise ratio of approximately 10(6) over a approximately 6 ns window at 55 fs time resolution (corresponding to the 9 THz source bandwidth) and a frequency/timing accuracy set by the frequency combs. The free-induction decay exhibits the expected periodic pulses from the rephasing of the multiply excited rovibrational levels. This demonstration represents the first high-resolution, high-accuracy, broadband measurement of optical free-induction decay, to our knowledge.
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