Direct-comb molecular spectroscopy with accurate, resolved comb teeth over 43 THz
Alexander M. Zolot, Fabrizio R. Giorgetta, Esther Baumann, Jeffrey W. Nicholson, William C. Swann, Ian R. Coddington, Nathan R. Newbury
We demonstrate a dual comb spectrometer using stabilized frequency combs spanning 176 THz to 219 THz (1370 nm to 1700 nm) in the near infrared. Measurements of amplitude and phase response at each individual comb tooth span the full 43 THz, generating ~430 000 individually resolved spectral elements at 100 MHz point spacing, each with kilohertz-level resolution and accuracy and signal-to-noise ratio of 100 to 6500. The SNR is within a factor of two of the shot-noise limit for direct-comb spectroscopy. Doppler-broadened phase and amplitude spectra of CO2, CH4, C2H2, and H2O in a 30 m multipass cell agree with established spectral parameters, emphasizing the dual-comb spectrometers ability to achieve high resolution measurements with optical bandwidth generally associated with blackbody sources.