Linear Birefringence

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

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

APPLICATIONS

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

PEMs

I/FS50 with NIO
I/FS50 with ARC

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)

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