The Faraday effect in diamagnetic glasses
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The Faraday effect in diamagnetic glasses Jianrong Qiu Hirao Active Glass Project, ERATO, JST-C, Keihanna Plaza, Seika-cho, Kyoto 61902, Japan
Kazuyuki Hirao Hirao Active Glass Project, ERATO, JST-C, 15 Morimoto-cho, Shimogamo, Sakyo-ku Kyoto 606, Japan, and Division of Material Chemistry, Faculty of Engineering, Kyoto University, Sakyo-ku, Kyoto 606-01, Japan (Received 30 March 1997; accepted 14 July 1997)
The wavelength dispersions of the Faraday effect in typical diamagnetic glasses, i.e., silica, borate, silicate, tellurite, lead-bismuth-gallate, and As2 S3 , have been examined. The Verdet constant of the glasses decreases with increasing wavelength in the longer wavelength region of the absorption edge of the glasses, while it increases with increasing optical bandgap of the glasses. These phenomena have been successfully explained based on the Becquerel theory. A guiding principle in designing a diamagnetic glass with a high Verdet constant is proposed.
I. INTRODUCTION
The Faraday effect is a phenomenon that the plane of polarization of a light beam transmitting through a material is rotated when the material is placed in a magnetic field. Glasses with a large Faraday effect are promising materials of magneto-optical switches, modulators, nonreciprocal elements in laser gyroscopes, optical circulators, laser isolators, and sensors of magnetic field and electric current,1–3 because glasses are homogeneous and can be easily fabricated in various forms such as fibers. Therefore, there have been many investigations on the Faraday effect in glasses up to now.4–9 The Faraday effect of diamagnetic glasses is temperature independent, while the Faraday effect of paramagnetic rare-earth-ions-containing glasses is affected by temperature.9 Therefore, diamagnetic glasses with a large Faraday effect are expected to be potential materials in the applications of optical switches and laser isolators, in which the temperature coefficient of the Verdet constant of glasses should be very small. Borrelli reported the Faraday effect in several oxide glasses in 1964.4 Glasses having Te41 as the glass former were observed to have relatively high Verdet constants. The large Verdet constant of the Tl1 -containing glasses was explained to be due to the larger oscillator strengths of the s 2 -sp transitions of Tl1 ion.4 However, to our knowledge, there are few systematic reports on the Faraday effect in the diamagnetic glasses. In this paper, we report the wavelength dispersions of the Faraday effect in typical diamagnetic glasses. The correlation between the magnitude of the Verdet constants and composition of the diamagnetic glasses is discussed. II. EXPERIMENTAL
Glass compositions used in this investigation are 100SiO2 (acronym SiO2 ), 20BaO ? 80B2 O3 (BaB), 1358
http://journals.cambridge.org
J. Mater. Res., Vol. 13, No. 5, May 1998
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20Na2 O ? 20CaO ? 60SiO2 (NaCaSi), 20Na2 O ? 80TeO2 (NaTe), 60PbO ? 20Bi2 O3 ? 20Ga2 O3 (PbBiGa), and 40As ? 60S (As2 S3 ) (m
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