Materials issues in the layers required for integrated magneto-optical isolators

The development of integrated optical isolators is critical to the functional integration of optical devices and systems. This work will primarily elucidate a methodology to grow, by a semiconductor compatible process, the critical active material in monolithically integrated magneto-optical isolators; yttrium iron garnet (YIG: Y₃Fe₅O₁₂). Reactive radio frequency (RF) sputtering was used to grow YIG on MgO, which is a promising buffer layer material for optical devices. The chemical, structural, optical, magneto-optical and magnetic properties of the resulting films have been studied by various techniques including energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Faraday rotation measurements and vibrating sample magnetometry (VSM). Low forward powers (lower limit of 12.3 W/cm²) grew YIG nuclei in an amorphous matrix and the number of these nuclei increased with increasing forward power. At powers exceeding 19W/cm² film cracking occurred. The films with YIG had strong in-plane magnetizations with small coercive fields. Optical cladding layers compatible with YIG films have been grown through plasma enhanced chemical vapor deposition (PECVD) and thin film permanent magnets for biasing have been grown and optimized.