This letter presents a polarimetric interferometer(PI) that can measure the ellipsometric parameter θ with an accuracy of 0.01 leading to a potential accuracy of 17 pm.The PI is constructed and compared with a commercial heterodyne interferometer(HI).Given its low nonlinearity,the PI is used to measure the residual nonlinearity of a heterodyne interferometric displacement system.A rotating half-wave plate is used to compensate for a part of the nonlinearity error caused by the misalignment of the axis between input polarizing states and beamsplitter.
