DETECTION OF MAGNETO-OPTIC EFFECT OF THE VACUUM-HIGH-SENSITIVITY POLARIZATION SPECTROSCOPY

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We investigated high-sensitivity polarization spectroscopy for detection of the magneto-optic effect of the vacuum.1) For detection of the ultra-small birefringence induced in the vacuum. Optical cavities are used to enhance the polarization signal. We proposed a polarization detection system in which a single cavity served two functions : signal enhancement and locking of a laser frequency. Using this system with a low finesse cavity we obtained the ' signal enhancement of 32 for the Faraday effect measurement. Meanwhile, we constructed a high-finesse cavity (F= 6 x 10^4 ), and investigated the optical anisotroy of the cavity mirrors using the polarization dependence cavity ring down method. We presented to minimize the anisotropy by optimization of the optical axes of the mirrors.2) We developed the high-sensitivity detection of the polarization signal for a single-pass arrangement. In order to reduce background noise we improved the extinction ratio of the polarization analyzer system to 10^<-10> so that the noise caused by intensity fluctuation of the light source was reduced to a level below that of shot noise. The minimum value that could be detected for the ellipticity change was 10^<-10> rad. We could detect the off-resonant Voigt effect of He gas that had the smallest value of the magnetically induced birefringence.The results thus obtained in the present study are useful for development of the polarization spectroscopic system to detect the magneto-optic effect of the vacuum