Spectropolarimetric measurement based on a fast-axis-adjustable photoelastic modulator

A fast-axis-adjustable photoelastic modulator (Faa-PEM) is developed and studied, and a spectropolarimetric imaging method using the Faa-PEM and an acousto-optic tunable filter is presented. The Faa-PEM modulation retardation amplitude and fast-axis direction of the Faa-PEM can be adjusted by adjusting the two drives with no mechanical rotation. The I, Q, and U of the Stokes parameters of the incident light can be obtained by adjusting the retardation amplitude and fast-axis direction of the Faa-PEM. This measurement method does not require high-frequency components, and thus a general area array detector can realize the measurement. Theoretical simulation analyses show that the relative errors Delta I/I, Delta Q/Q, Delta U/U, and Delta DoLP/DoLP are less than 5.6% and that the deviation error Delta AoLP is less than 0.2 degrees (at I = 1.00, Q = 0.707, U = 0.707, V = 0.0, -0.1 degrees <= Delta theta(0) < 0.1 degrees, and -0.05 rad <= Delta delta(0) <= 0.05 rad). A prototype was developed and tested. The test results show that the average absolute relative error of the degree of linear polarization is 0.36%, and the average absolute deviation error of the angle of linear polarization is 0.048 degrees. The method has potential application value in spectropolarimetric imaging technology. (C) 2019 Optical Society of America