MODULATORS :: APPLICATIONS :: Low-level Linear Birefringence 

The residual 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



EQUATION



B: linear birefringence of a sample
I_1f: 1f signal
I_DC: DC signal
A₀: PEM’s retardation setting
J₀(A₀): the 0th order Bessel function
J₁(A₀): 1st order Bessel function


In reality, due to different amplification gains being used for the AC and DC signal channels, a calibration with a known birefringence is normally used.



APPLICATIONS

RESOURCES

Linear Birefringence Application Note

In optical materials; laser optics; quality control of optics, glasses, and thin films


TYPICAL PEM
I/FS50w/NIO

OTHER INSTRUMENTATION
Exicor^® Birefringence Measurement Systems

FURTHER READING

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).