Monolithically integrated optical isolator chips with sputter-coated Ce:YIG films on silicon waveguides

This paper presents an experimental demonstration of monolithically integrated optical isolator chips with sputter-coated Ce:YIG films on silicon waveguides, using the nonreciprocal phase shift effect of a Mach-Zehnder-type interferometer. A fully CMOS-compatible optical isolator chip has been developed, achieving 27.7 dB of optical isolation and 6.4 dB of insertion loss at an input wavelength of 1550 nm. The isolator chip has an area of 220 × 1310 µm 2 and can be readily integrated with other silicon photonic devices to enable complete photonic integrated-circuit applications. This initial result indicates that monolithically integrated optical isolators, produced via mass-producible sputtering to deposit MO films directly on silicon waveguides, are feasible for large-scale manufacturing. Additionally, chip performance can be further enhanced by optimizing waveguide structures and magneto-optic film-coating conditions. The high-temperature annealing processes commonly used to crystallize MO films can be replaced by localized laser annealing.