Temperature independent Faraday rotation near the band gap in Cd1−xMnxTe

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Abstract
Faraday rotation spectra have been measured for Cd1−xMnxTe, 0.10≤x≤0.20, for temperatures from 213 to 373 K. At wavelengths well above the fundamental absorption edge the rotation decreases with increasing temperature. The opposite temperature dependence is found for shorter wavelengths since the rotation increases strongly when the wavelength approaches the edge and the edge moves towards longer wavelengths with increasing temperature. For each x a wavelength with temperature independent rotation can be found due to a cancellation of these effects. The large and temperature independent rotation is of great interest for optical devices such as magnetic field sensors, isolators, and modulators. By choosing 0.10≤x≤0.25 these devices would be compatible with GaAlAs emitting diodes and lasers. Optical transmission was also measured and was found to be fairly high at wavelengths of interest. A sensor design is presented, allowing dc response and very small physical dimensions.