Research on measuring polarization state of light by Stokes parameters based on electro-optic effect

Abstract

The polarization information of light can be used to improve the possibility of target recognition. Stokes parameters can express all kinds of polarization states compared with the Jones matrix. Many ways have been developed to measure light polarization state by Stokes parameters. But traditional systems meet challenges in stability and velocity. A new method was proposed in this paper to apply two cascaded LiNbO3 crystals as a phase retarder in replacing the wave plate. It has the merits of static without moving elements and rapid measurement. The transversal electro-optic effect is exploited to avoid the high voltage loaded on a LiNbO3 crystal. Four different voltages were loaded on eight LiNbO3 crystals respectively to obtain four values of related phase difference and four intensity values recorded on the detector one time, from which the Stokes parameters of the detected light can be obtained to express the light polarization state. This system has the possibility to measure high speed changing polarized light even less than microseconds. The experiments were performed to prove the feasibility of this proposed method. The calculated polarization state is close to the expected Stokes parameters for the linearly and circularly polarized light. It is suitable for the fields demanding stable and real-time monitoring the changing of polarization state.