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.

High Speed Sub-GHz Spectrometer for Brillouin Scattering Analysis.

The goal of this protocol is to build a parallel high-extinction and high-resolution optical Brillouin spectrometer. Brillouin spectroscopy is a non-contact measurement method that can be used to obtain direct readouts of viscoelastic material properties. It has been a useful tool in material characterization, structural monitoring and environmental sensing. In the past, Brillouin spectroscopy has usually employed scanning Fabry-Perot etalons to perform spectral analysis. This process requires high illumination power and long acquisition times, making the technique unsuitable for biomedical applications. A recently introduced novel spectrometer overcomes this challenge by employing two VIPAs in a cross-axis configuration. This innovation enables sub-Gigahertz (GHz) resolution spectral analysis with sub-second acquisition time and illumination power within the safety limits of biological tissue. The multiple new applications facilitated by this improvement are currently being explored in biological research and clinical application.