Dark-Fringe Interferometry for Infrared Sensing

Achieving sensitive absorption detection using optical frequency comb spectroscopy requires increasing interaction length with the sample, using multipass cells or optical cavities, or cancelling the laser envelope contribution. Optical cavities enable orders of magnitude gain in sensitivity, but at the expense of a reduced spectral coverage. On the other hand, background suppression techniques using destructive interference, or dark fringe (DF), open up for absorption spectroscopy with a signal-to-noise ratio limited by the quantum noise of the absorbed photons only. A few approaches have exploited this technique for absorption spectroscopy. They rely on a stabilized interferometer at zero-path difference and measure the residual interference when a sample is placed in one of the arms, using optical spectrum analyzer [1], dual-comb spectroscopy [2], or correlation spectroscopy [3].