High-finesse sub-GHz-resolution spectrometer employing VIPA etalons of different dispersion

We report a novel configuration of a two-stage virtually imaged phased array spectrometer that enables high-throughput sub-GHz spectroscopy at a high finesse (>750). Two etalons with different free spectral range and different dispersion are arranged in an orthogonal direction and spread the spectrum across two dimensions, with a greatly improved rejection ratio of white-light background noise. A proof-of-concept application for Brillouin spectroscopy is demonstrated. (C) 2015 Optical Society of America