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

Masanori Abe, Keiji Shono and Manabu Gomi

(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.

URL: http://jjap.jsap.jp/link?JJAP/21/1337/
DOI: 10.1143/JJAP.21.1337

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