White-light versus discrete wavelength measurements of Faraday dispersion and the Verdet constant

The wavelength dependence of the Faraday effect may be measured either sequentially at particular wavelengths using narrow band sources, or simultaneously at many wavelengths using a white-light or broadband source. We apply both methods to measure the wavelength dependence of the Verdet constant of a terbium gallium garnet crystal. We show that although the white-light measurement offers the advantage of requiring only one source, it is more prone to systematic errors than using multiple laser sources.