Direct determination of azimuth angles in photoelastic modulator system

Abstract

Instead of the nulling method, a high-level intensity technique is proposed to determine the relative azimuth orientation of a photoelastic modulator and an analyzer. In a photoelastic modulating system, one can obtain a DC intensity distribution by varying the phase modulation amplitude at two azimuth angles of the analyzer, which are pi/4 apart from each other. The relative azimuth orientation can be determined by taking the ratio of the slopes of these two intensity distributions around the linear region of the zero point of the zero-order Bessel function. A similar technique is also applicable to wave plates for aligning their optical axes with the system.