Faraday Rotation of Dy₂O₃, CeF₃ and Y₃Fe₅O₁₂ at the Mid-Infrared Wavelengths

The relatively narrow choice of magneto-active materials that could be used to construct Faraday devices (such as rotators or isolators) for the mid-infrared wavelengths arguably represents a pressing issue that is currently limiting the development of the mid-infrared lasers. Furthermore, the knowledge of the magneto-optical properties of the yet-reported mid-infrared magneto-active materials is usually restricted to a single wavelength only. To address this issue, we have dedicated this work to a comprehensive investigation of the magneto-optical properties of both the emerging (Dy${}_2$O${}_3$ ceramics and CeF${}_3$ crystal) and established (Y${}_3$Fe${}_5$O${}_{12}$ crystal) mid-infrared magneto-active materials. A broadband radiation source was used in a combination with an advanced polarization-stepping method, enabling an in-depth analysis of the wavelength dependence of the investigated materials’ Faraday rotation. We were able to derive approximate models for the examined dependence, which, as we believe, may be conveniently used for designing the needed mid-infrared Faraday devices for lasers with the emission wavelengths in the 2-$\mathsf{\mu }\mathrm{m}$ spectral region. In the case of Y${}_3$Fe${}_5$O${}_{12}$ crystal, the derived model may be used as a rough approximation of the material’s saturated Faraday rotation even beyond the 2-$\mathsf{\mu }\mathrm{m}$ wavelengths.