High-contrast Brillouin spectrometer based on a hybrid VIPA-etalon cascade scheme

Brillouin spectroscopy is increasingly employed for biomedical research and recent advances such as line-scanning configurations further widen the scope of possible measurements. Current spectrometer technologies have limitations which are prohibitive for certain applications. We propose a novel hybrid VIPA-etalon cascade scheme compatible with both confocal and line-scanning geometries. A single VIPA is followed immediately with one or multiple essentially parallel-oriented standard Fabry-Perot etalons of approximately matching thickness. The cascaded etalons preserve near-unity throughput while increasing the contrast by more than 20 dB per stage. Other advantages include simplicity, compactness, and wavelength flexibility. We present simulations of the hybrid VIPA-etalon scheme and an experimental proof-of-concept measurement.