Quantum-noise-limited Optical Frequency Comb Spectroscopy

Phys Rev Lett. 2011 Dec 2;107(23):233002. doi: 10.1103/PhysRevLett.107.233002. Epub 2011 Nov 28.


We achieve a quantum-noise-limited absorption sensitivity of 1.7×10(-12) cm(-1) per spectral element at 400 s of acquisition time with cavity-enhanced frequency comb spectroscopy, the highest demonstrated for a comb-based technique. The system comprises a frequency comb locked to a high-finesse cavity and a fast-scanning Fourier transform spectrometer with an ultralow-noise autobalancing detector. Spectra with a signal-to-noise ratio above 1000 and a resolution of 380 MHz are acquired within a few seconds. The measured absorption line shapes are in excellent agreement with theoretical predictions.