Longhai Liu

Simultaneous measurement of birefringence magnitude and direction using Wollaston prism

Simultaneous measurement of the birefringence magnitude and direction using Wollaston prism is presented. The sinusoidally modulated laser beam passes through a circular polarizer, the birefringence sample and is split by a Wollaston prism. The measuring beam is then detected by a bi-cell detector and two alternating current signals are detected. Then the Wollaston prism is rotated by 45°, and another two alternating current signals are obtained. By processing the four signals, the birefringence magnitude and direction is resolved simultaneously. In experiments, a wedge waveplate was laterally moved and measured at different birefringence magnitude. The measured birefringence magnitude linearly increased as the wedge waveplate was laterally moved. The maximum standard deviation of the birefringence magnitude and direction is 0.11° and 0.05°The usefulness of this method is verified.

Real-time Measurement of Full Field Retardation near Quarter Wavelength

A real-time method to measure full field retardation near quarter wavelength is proposed. The circularly polarized beam passes through a sample with a large aperture. The measuring beam then goes through a quarter-wave plate and is then split by a Wollaston prism. An image with two sub-images is then detected by a high-speed image sensor. The full field retardation near quarter wavelength can be obtained in real time by processing the image. The measured retardation is independent of the fast axis angle of the sample and the fluctuation of the initial intensity. In experiments, a wedge waveplate is measured with different fast axis angle and initial intensity, and the full field retardations are acquired. The maximum and standard deviation of the full field retardation is 1.5° and 0.4°. The validity of the method is verified.