Integration of spectral coronagraphy within VIPA-based spectrometers for high extinction Brillouin imaging

TL;DR

This paper presents a novel integration of spectral coronagraphy into VIPA-based spectrometers, significantly enhancing their ability to perform high-extinction Brillouin imaging in scattering media and near reflective interfaces.

Contribution

The authors adapt coronagraph design from exosolar imaging to spectral domain, achieving up to 20dB extinction increase in VIPA spectrometers without additional insertion loss.

Findings

Achieved up to 20dB spectral extinction enhancement.

Enabled Brillouin imaging near reflective interfaces without index matching.

Demonstrated improved performance in scattering media.

Abstract

VIPA-based spectrometers have enabled rapid Brillouin spectrum measurements and current designs of multi-stage VIPA spectrometers offer enough spectral extinction to probe transparent tissue, cells and biomaterials. However, in highly scattering media or in the presence of strong back-reflections, such as at interfaces between materials of different refractive indices, VIPA-based Brillouin spectral measurements are limited. While several approaches to address this issue have recently been pursued, important challenges remain. Here we have adapted the design of coronagraphs used for exosolar planet imaging to the spectral domain and integrated it in a double-stage VIPA spectrometer. We demonstrate that this yields an increase in extinction up to 20dB, with nearly no added insertion loss. The power of this improvement is vividly demonstrated by Brillouin imaging close to reflecting interfaces without need of index matching or sample tilting