The Faraday effect and magneto-optical figure of merit in the visible region for lithium borate glasses containing

Faraday-effect measurements have been carried out at room temperature for -containing lithium borate glasses to evaluate the magneto-optical figure of merit in the wavelength range of 350-850 nm. The magneto-optical figure of merit tends to increase with decreasing wavelength except for the range within which absorption bands due to the 4f-4f transitions are observed. Glasses with low content and high concentration of exhibit fairly large magneto-optical figures of merit at around 400 nm which corresponds to the emission wavelength of the (Ga, In)N laser diode; the magneto-optical figure of merit of glass is more than at 400 nm under an external magnetic field of 15 kOe. The analyses of the wavelength dependence of the Verdet constant indicate that the magnitude of the Verdet constant is large because the effective transition probability is high, coincident with the early suggestion by Shafer and Suits [ J. Am. Ceram. Soc. 49 (1966) 261]. This suggests that the magnitude of the Verdet constant remains large even in the wavelength range far from the position of the optical absorption peak due to the 4f-5d transition which causes the Faraday effect. Because the absorbance due to the 4f-5d transition is low in such a wavelength range, the -containing glasses show large magneto-optical figures of merit.