Surachai Nopparatjamjomras, Rachapakaya Chitaree, and Choenchok Soankwan

pp. 285 - 294

Abstract

Stokes parameters are used to describe the polarization state of the beam. The Stokes parameters can
be used to analyze the properties of a sample in terms of retardation and specific rotation. As several conventional instruments for measuring the Stokes parameters involve many procedures and a lot of time is required, the application area is limited. Therefore, to lessen the measuring period and widen the application
area, in this research, an automatic instrument for determining the state of polarization based on a technique
employing Fourier analysis coupled with some simple computer controlled electronic circuits are proposed.
The technique of this measurement is called “Fourier analysis using a rotating quarter wave plate”. This
system is composed of a rotating quarter wave plate controlled by a stepping motor, a fixed linear horizontal
polarizer and a detector. The intensities obtained from the receiving detector are analyzed with Simpson 's
method and Fourier Analysis to calculate the Stokes parameters. The performance of the instrument was
preliminary examined by measuring several known polarized beams. In addition, the instrument was used as
a tool to determine the specific rotation of D-glucose and phase shift of known retardances. The experimental
results were found to be in agreement with theoretical results.