Imparting memory functionality to planar waveguide structures with photo-magnetic materials

A waveguide-type Mach-Zehnder interferometer (WG-MZI) incorporating a magnetic layer on each of two WG branches is proposed for use in an all-optical memory cell. The key concept is switching the relative magnetization configuration between parallel and anti-parallel with photonic or electronic excitation, which alters the interference condition of the WG-MZI and thus varies the intensity of its output light. In the present work, photo-excited precession of magnetization is assumed as a trigger for magnetization switching. The magnitude of changes in the effective refractive index (Delta n(M)) in the WG region optically coupled with magnetization and the output light intensity (Delta I) are studied theoretically by model calculation based on magneto-optical (MO) phase delay, through which target and practical values of Delta n(M) and Delta I are examined. Experimental works on the preparation and characterization of ultra-thin Co/Pd multi-layers are described as a prototype magnetic system for the proposed optical memory due to their large photo-induced precession angle. (C) 2020 The Japan Society of Applied Physics