Optimal multi-spectrum polarization detection with full-Stokes in a single channel by using standard retarders

• The implement of stable optimal full-Stokes multi-spectral polarization detection (MPD) is a challenging. • Any pair of standard retarders can generate required retardance at different wavelength. • Dual rotatable linear retarders can optimise MPD system by maintaining special retardance. • Dual-retarders MPD system has optimal performance and higher measurement accuracy. Polarization detection with full-Stokes is one of the important way to obtain spatial distribution and physical information on targets. However, the most full-Stokes multi-spectrum polarization detection system is relatively complex, as the traditional method is generally designed for multi-channel to adapt the different wavelength. In this paper, we propose an optimal polarization detection method to obtain the full-Stokes vector of the incident light in one channel for different wavelengths. This method utilizes two standard retarders for multi-spectrum full polarization modulation, which can obtain accurately the desired retardance to achieve optimal system performance at multi-wavelengths. The numeric analysis validates the feasibility of the dual-retarders detection system based on tunable polarization retardance method. Furthermore, in experiments, just two much more readily available quarter-wave plate (QWP) retarders are utilized, the various special retardance within 0.2° errors and high polarization measurement accuracy below 10 -2 level at multi-wavelengths are achieved. This method, with a simple structure, has excellent application prospects in high-precision polarization detection, such as solar magnetic field detection.