An effective method for improving linear and circular birefringence sensitivity

Reflection linear birefringence (RLB) and Magneto-optical Kerr effect (MOKE) measurement are powerful linear optical tools to study materials’ symmetry properties, i.e., rotational and time-reversal symmetry breaking, respectively. In principle, RLB and MOKE only require a simple balanced detection setup that could detect polarization change of the light after being reflected by the sample. However, building a sensitive and powerful setup, especially for wavelength and polarization dependent measurements, is a nontrivial task due to the difficulty in removing inevitable, and often not-so-weak, artifacts generated by the optical components along the light path. Here, an artifact elimination method is introduced and tested. We will compensate the artifacts by fine tuning the balancing in a systematic and reproducible way for each measurement parameters, i.e., wavelength and polarization. We will show that we can successfully suppress the RLB artificial background by two order magnitude and verify that this method is effective for a wide tunable wavelength range. We will finally show its demonstration on atomically thin van der Waals films, with a comparison to numerical simulations.