Dual frequency comb Fourier transform spectroscopy
Ian R. Coddington, William C. Swann, Nathan R. Newbury
Dual coherent frequency combs can be used in Fourier transform spectroscopy (FTS) to generate the full optical response of a sample with high frequency, and time, accuracy and resolution. The approach can be viewed equally well as a multiheterodyne, coherent Fourier transform, or time-domain spectroscopy. We discuss the performance and design of a coherent dual-comb FTS system in the near infrared that uses two coherent fiber frequency combs phase-locked to each other and to an underyling cw optical reference. We measure the fully normalized, complex response of a gas sample over 9 THz of spectrum at 200 MHz frequency resolution yielding 45,000 resolution elements. The average spectral signal-to-noise ratio (SNR) is 2,500 for both the fractional absorption and the phase in radians, with a peak SNR of 4,000. The corresponding time-domain SNR is 0.6×10^6. We describe the overall experimental system and provide example data illustrating the performance.
Physical Review A (Atomic, Molecular and Optical Physics)
Fourier transform spectroscopy, frequency comb, FTS, Spectroscopy