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Abstract: We measure the infrared wavelength 11 - 0.8 microns; energy E = 0.1 - 1.5eV Faraday rotation and ellipticity in GaAs, BaF2, LaSrGaO4, LaSrAlO4, andZnSe. Since these materials are commonly used as substrates and windows ininfrared magneto-optical measurements, it is important to measure their Faradaysignals for background subtraction. These measurement also provide a rigoroustest of the accuracy and sensitivity of our unique magneto-polarimetry system.The light sources used in these measurements consist of gas and semiconductorlasers, which cover 0.1 - 1.3 eV, as well as a custom-modified prismmonochromator with a Xe lamp, which allows continuous broadband measurements inthe 0.28 - 1.5 eV energy range. The sensitivity of this broad-band system isapproximately 10 micro-rad. Our measurements reveal that the Verdetcoefficients of these materials are proportional to $1-\lambda^2$, which isexpected when probing with radiation energies below the band gap. Reproducibleellipticity signals are also seen, which is unexpected since the radiation iswell below the absorption edge of these materials, where no magnetic circulardichroism or magnetic linear birefringence should occur. We suggest that theFaraday ellipticity is produced by the static retardance Rs of thephotoelastic modulator PEM and other optical elements such as windows, whichconvert the polarization rotation produced by the sample into ellipticity. Thisstatic retardance is experimentally determined by the ratio of the Faradayrotation and ellipticity signals, which are induced by either applying amagnetic field to a sample or mechanically rotating the polarization of lightincident on the PEM and-or other optical components.



Author: M.-H. Kim, V. Kurz, G. Acbas, C. T. Ellis, J. Cerne

Source: https://arxiv.org/



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