The presence of residual low-level linear birefringence in an optical component affects its quality, especially when used in polarization related instruments. The PEM can be applied to the measurement of linear birefringence of transparent optical materials in several different ways.
ONE EXAMPLE OF THE COMMON SETUPS
B: linear birefringence of a sample
I1f: 1f signal
IDC: DC signal
A0: PEM’s retardation setting
J0(A0): the 0th order Bessel function
J1(A0): 1st order Bessel function
In practice, due to different amplification gains being used for the AC and DC signal channels, a calibration with a known birefringence is normally used.
In optical materials; laser optics; quality control of optics, glasses, and thin films
J. C. Kemp, Basic Laboratory set-up for various measurements possible with the photoelastic modulator, Application note, Hinds Instruments, Inc. (1975)
J. Schellman and H. P. Jensen, “Optical Spectroscopy of Oriented Molecules,” Chem. Rev. 87, 1359-1399 (1987)
S. J. Johnson, “Simultaneous dichroism and birefringence measurements of sheared colloidal suspension in polymeric liquids," Ph. D thesis, Stanford Univ. (1985).
T. C. Oakberg, “Measurement of Low-level Strain Birefringence in Optical Elements Using a Photoelastic Modulator,” SPIE, 2873, 17-20 (1996)
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