About the systematic errors of the retrieved linear depolarisation ratio due to rotated laser polarisation and rotated polarisation calibrator

Ludwig-Maximilians-Universität, Meteorologisches Institut, Theresienstr. 37, 80333 München, Germany Lead Author e-mail address: This email address is being protected from spambots. You need JavaScript enabled to view it.

Published online: 9 April 2026

Abstract

The optical elements of lidar systems can induce polarisation effects in the laser beam passing through them, depending on the state of polarisation of the laser beam before them. Therefore, an unaccounted for rotation α of the polarisation of the emitted laser beam can introduce a systematic error to the measured linear depolarisation ratio δ. An experimental method to correct δ for this misalignment is to compensate it by the half-wave plate (HWP) that is placed as a polarisation calibrator before the polarising beam-splitter cube (PBS) of the lidar receiver. But in this way a new systematic error in δ can be introduced. In this study we investigate with a simulation for which lidar systems this error could be significant. Our results indicate the need to determine the rotation angle of the linear polarisation of the laser beam and to keep it smaller than 5^o. If this angle is unknown, a systematic error of the volume linear depolarisation ratio of up to 0.07 can result - and should be considered.