A Mueller matrix approach to flat gold mirror analysis and polarization balancing for use in retinal birefringence scanning systems

In a polarization-sensitive optical system, it is important to understand the effects that mirrors have on polarization at a specific wavelength of interest, angle of incidence, reflective material, coating, etc. When modeling reflection, the optical designer oftentimes needs to know the Mueller matrix for the particular mirror, in order to assess its overall impact on polarization and possibly reduce the mirror-related effects in the entire system's performance. Based on an example of a protected gold flat mirror, we investigated two methods, one analytical and one experimental, for determining the Mueller matrix of a noble metallic mirror. The measured Mueller matrix was shown to be nondepolarizing. Then, using polar decomposition, the measured matrix was interpreted as a combination of a pure retarder and a diattenuator. Further investigation showed that the diattenuation property was very weak, which offered the opportunity of largely balancing the introduced polarization deviation by means of a linear compensating retarder. The results of this work were used successfully for improving the design of a diagnostic device for ophthalmology based on retinal birefringence scanning. The described approach also greatly improves the precision of Mueller-matrix-based computer modeling of polarization sensitive systems.