Faraday Rotation of Rare-Earth (III) Phosphate Glasses

The optical Faraday rotation of trivalent rare-earth phosphate glasses has been investigated at room temperature. The rotation is ascribed primarily to strong electric dipole transitions involving the rare-earth $4f$ electrons and is described as a function of the incident light wavelength by a simplified equation involving an effective transition wavelength. The linear dependence of the rotation on the concentration is experimentally demonstrated. The relative magnitudes of the magnetic rotation of the rare-earth ions are compared to the quantity $\frac{p^2}{g}$, where $p$ is the effective magneton number and $g$ is the spectroscopic splitting factor. This comparison demonstrates the importance of the other parameters, especially the transition wavelengths and electric dipole matrix elements. It also indicates that a prediction of relative rotations of ions, molecules, etc., on the basis of relative magnitudes of magnetic susceptibility and concentration alone is not meaningful.