Wave-plates are an important optical component for light polarization-related measurements. The PEM can be employed to determine both the amplitude and orientation of the retardation of a wave-plate.
I1f: 1f signal
I2f: 2f signal
A0: PEM’s retardation setting
J2(A0): 2nd order Bessel function
J1(A0): 1st order Bessel function
In this set-up, either the fast axis or the slow axis of the quarter-wave plate is required to be parallel to the PEM’s optical axis. The positive and negative signs of I2f, after calibration, indicate which axis (slow or fast) it is.
Wave-plate inspection and characterization
J. C. Kemp, Basic Laboratory set-up for various measurements possible with the photoelastic modulator, Application note, Hinds Instruments, Inc. (1975)
T. C. Oakberg, “Measurement of Wave-plate Retardation Using a Photoelastic Modulator,” SPIE, 3121, 19-22 (1997)
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