Nanomagnetic route to bias-magnet-free, on-chip Faraday rotators

The miniaturization of Faraday rotator elements is of interest in optical telecommunications for the production of small isolator components. Here we discuss the fabrication of bias-magnet-free-waveguide Faraday rotators for ultrasmall planar device applications. Photonic-crystal structures on magnetic films can yield a significant enhancement in magneto-optic rotation efficiency and an overall reduction in device dimensions. By introducing single-domain magnetic nanoparticles as defects in the photonic bandgap, we show that one can maintain a high degree of coercivity in the Faraday rotator, thus obviating the need for external magnets. We present a theoretical discussion of the formation of single-domain particles in magnetic garnet films, their reversal field characteristics, and the waveguide properties and magneto-optic response of photonic crystals with single-domain defects.