Optically Induced Magnetization in Ruby

Abstract

A time varying macroscopic magnetization of ruby is observed at room temperature by selectively exciting the Cr³⁺ ions with a right- and a left circularly polarized light of a Q-switched ruby laser from one of the ground ⁴A₂ multiplets to a proper component of the upper \barE(²E) multiplets. Dependence of such a magnetization in the Z-direction on the irradiation power, the ellipticity and the magnetic field was measured with a pick-up coil. The signal had a value of 1.7×10⁻⁴ emu/g at the irradiation of 67 mJ. The relaxation time of the ground state was estimated from the decay to be about 180 ns in zero magnetic field. The signal changed with the ellipticity of the exciting light, and the amplitude of the signal was always proportional to the intensity of the excitation. These experimental results were quantitatively explained by a theoretical analysis for the time varying optically induced magnetization.