Jpn. J. Appl. Phys. 21 (1982) pp. 1337-1341 |Next Article| |Table of Contents|
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Signal-to-Noise Ratio in Polarization Modulation Method for Magneto-Optical Measurement
Department of Physical Electronics, Tokyo Institute of Technology
(Received December 21, 1981; accepted for publication June 19, 1982)
The signal-to-shot-noise ratio (SNR) in the polarization modulation method using a photomultiplier for measuring a magneto-optic rotation angle \varPsi is calculated as a function or the modulation amplitude a0, taking the magneto-optic ellipticity angle χ, the extinction ratio of the polarizer, and the partial polarization of the light source into account. The SNR increases to a saturation value of (S/N)0 as a0 increases, in accordance with the formula S/N=(S/N)0 [1+(2\varPsi2+4\varGamma')/a02]-1/2. Here, \varGamma' is the `practical extinction ratio' of the polarizer, in which the influence of the ellipticity χ as well as the influence of the partial polarization of the light source are included. The SNR measurement was performed at λ=0.63 µm, using a monochromator and polarizers of the Glan-Thompson or dichroic-sheet type. The reult agrees with our calculation.
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