Faraday Rotation of Semiconductors
Due to spin-orbit coupling, undoped GaAs single crystal exhibits much larger Faraday rotation than glass (SiO2). Considering the atomic arrangement is different along the (100) and (110) plane, one might think the Faraday rotation is polarization dependent. However, experimental work revealed an immeasurable anisotropy in the wavelength range from 880 to 1600 nm. Based on the large Faraday rotation, one might be able to use GaAs to calibrate the B field of the Tera Hertz electromagnetic wave which requires very fast response time. Around the band gap, the Faraday effect shows resonance behavior. More generally, (ferromagnetic) semiconductors return both electro-gyration and a Faraday response in the high frequency domain. The combination of the two is described by gyroelectromagnetic media, for which gyroelectricity and gyromagnetism (Faraday effect) may occur at the same time.
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