Small magnetless integrated optical isolator using a magnetized cobalt ferrite film

Abstract

We experimentally demonstrated a silicon optical isolator using a monolithically integrated cobalt ferrite (CFO) film as magneto-optical material, achieving an isolation ratio of 9.6dB near 1550nm wavelength. By virtue of the large Faraday rotation coefficient of CFO, the device has a compact footprint comparing to the current yttrium iron garnet-based isolators. Furthermore, we demonstrated self-biased isolation by the strong remanence of CFO films, eliminating the tedious demand of an external magnet. Cobalt ferrite represents a potential alternative approach to yttrium iron garnets to realize a practical device for on-chip isolation in silicon photonic integrated circuits because of the small footprint.