Abstract
An electro-optic modulated circular heterodyne interferometer using the phase-lock technique for measuring the circular birefringence in chiral medium is proposed. The validity of the proposed design is demonstrated by the measurement of rotation angle of the chiral medium such as a half-wave plate and the glucose sample. The average relative error in rotation angle level of 0.00284° has been obtained for a solid half-wave plate, with a correlation coefficient of 0.9999975 indicates a good linear response. Moreover, the standard deviation in rotation angle level of 0.005275° has been obtained for glucose solutions with concentrations ranging from 0-1.2 g/dl in 0.2 g/dl increments, with a correlation coefficient of 0.99915 between the reference and the measured values. Consequently, the proposed apparatus has advantages of a simpler structure, fewer optical elements, tunable heterodyne frequency, and easy signal processing. The linearity and resolution characteristics of this system are comparable to those previous studies adopting phase sensitive techniques. This apparatus enables not only the measurement of the circular birefringence successfully in the phase-lock technique, but also the integration with previously developed linear birefringence measurement system.
