A novel apparatus to measure small magnetic birefringences is described. It is based on a high-finesse Fabry–Perot cavity, to which a Nd:YAG laser is frequency locked, and on a 1.1-T permanent dipole magnet. We report the new measurement of the magnetic anisotropy of the refraction index (Cotton–Mouton effect) for molecular oxygen at λ=1064 nm, T=20 °C. Our result, Δn(O<sub>2</sub>)=(−2.29±0.08)10<sup>−12</sup>(B/1 T)<sup>2</sup>(P/1 atm), is consistent with the existing theoretical predictions and falls in line with the previous experimental results taken at different wavelengths.
© 1998 Optical Society of America
(120.2130) Instrumentation, measurement, and metrology : Ellipsometry and polarimetry
(120.2230) Instrumentation, measurement, and metrology : Fabry-Perot
(210.3820) Optical data storage : Magneto-optical materials
(260.1440) Physical optics : Birefringence
F. Brandi, F. Della Valle, P. Micossi, A. M. De Riva, G. Zavattini, F. Perrone, C. Rizzo, and G. Ruoso, "Cotton–Mouton effect of molecular oxygen: a novel measurement," J. Opt. Soc. Am. B 15, 1278-1281 (1998)