Improved common-path optical heterodyne interferometer for measuring small optical rotation angle of chiral medium

An improved common-path optical heterodyne interferometry for measuring small optical rotation angle of chiral liquid is presented. The optical rotation angle can be determined by the phase difference between the test and reference signals. By means of inserting a phase retarder behind the test sample, the measuring resolution of optical rotation angle is greatly enhanced. The theoretical prediction indicates the resolution is better than 3.5 × 10−5 degree.