Broadband cavity-enhanced molecular spectra from Vernier filtering of a complete frequency comb

We present a new approach to cavity enhanced-direct frequency comb spectroscopy where the full emission bandwidth of a titanium: sapphire laser is exploited, currently at gigahertz resolution. The technique is based on lowresolution Vernier filtering obtained with an appreciable actively stabilized mismatch between the cavity-free spectral range and the laser repetition rate, using a diffraction grating and a split-photodiode. Spectra covering 1300 cm(-1) (40 THz) are acquired in less than 100 ms, and a baseline noise of 1.7 x 10(-8) cm(-1) is reached with a cavity finesse of only 300, providing an absorption figure of merit M = 6 x 10(-11) cm(-1) . Hz(-1/2). (C) 2014 Optical Society of America