# Detector bandwidth and polarisation switching rates: spectrophotometric observations of the Sun by the Birmingham Solar Oscillations Network (BiSON)

## TL;DR

This study evaluates a commercial liquid crystal retarder as a cost-effective alternative to custom Pockels-effect cells for polarisation switching in solar oscillation observations, potentially simplifying instrumentation.

## Contribution

It demonstrates that off-the-shelf liquid crystal retarders can replace bespoke Pockels-effect cells, maintaining performance while enabling easier and faster deployment.

## Key findings

- Liquid crystal retarder is a viable replacement for Pockels-effect cells.
- Slower switching rate of LCD retarder is acceptable for the application.
- Simplified instrumentation deployment is achievable with off-the-shelf components.

## Abstract

The Birmingham Solar Oscillations Network (BiSON) observes acoustic oscillations of the Sun. The dominant noise source is caused by fluctuations of Earth's atmosphere, and BiSON seeks to mitigate this effect by combining multiple rapid observations in alternating polarisation states. Current instrumentation uses bespoke Pockels-effect cells to select the polarisation state. Here, we investigate an alternative off-the-shelf solution, a liquid crystal retarder, and discuss the potential impact of differences in performance. We show through electrical simulation of the photodiode-based detectors, and assessment of both types of polarisation device, that although the switching rate is slower the off-the-shelf LCD retarder is a viable replacement for a bespoke Pockels-effect cell. The simplifications arising from the use of off-the-shelf components allows easier and quicker instrumentation deployment.