TITLE:
Interferometry Analysis of Cellophane Birefringence
AUTHORS:
Dickson M. Kinyua, Geoffrey K. Rurimo, Patrick M. Karimi, Stephen N. Maina, Calvin F. Ominde
KEYWORDS:
Cellophane Sheet; Birefrigence; Interferrogram; Polarization
JOURNAL NAME:
Optics and Photonics Journal,
Vol.3 No.6,
October
22,
2013
ABSTRACT: This paper reports on a simple approach of determining the
ability of a transparent material, such as cellophane to rotate the direction of
polarization of a light beam. In order to determine the birefringence of such a
material, a Mach-Zehnder interferometer is used to generate interference patterns
when the cellophane sheet is mounted on one arm such as to intercept a portion of
the laser beam. The recorded interferograms show a phase shift which is calculated
to be 0.98π radians. By rotating the cellophane sheet on the
object beam, the fringe separation is measured for different angles and the values
used to calculate the ordinary and extraordinary refractive indices as 1.4721 ± 0.0002 and
1.4680 ± 0.0002 respectively at 632.8 nm wavelength. A surface error of approximately λ/16 (peak to valley) is measured from
the recorded interferograms. Because of its sufficient birefringence and small thickness
of 24 μm, cellophane can be used to fabricate special polarization pupil masks by
cutting and aligning different cellophane structures appropriately.