Tunable Polarized Microcavity Characterized by Magnetic CircularDichroism Spectrum

Tunable resonator is a powerful building block infields like colorfiltering andoptical sensing. The control of its polarization characteristics can significantly expand theapplications. Nevertheless, the methods for resonator dynamic tuning are limited. Here, amagnetically regulated circular polarized resonant microcavity is demonstrated with anultrathin ferrimagnetic composite metal layer Ta/CoTb. We successfully tuned the cavityresonant frequency and polarization performance. A huge magnetic circular dichroism (MCD)signal (similar to 3.41%) is observed, and the microcavity valley position shifts 5.41 nm when a smallmagneticfield is applied. This resonant cavity has two-stable states at 0 T due to the magneticremanence of CoTbfilm and can be switched using a tiny magneticfield (similar to 0.01 T). Our resultshows that the ferrimagneticfilm-based tunable microcavity can be a highly promisingcandidate for on-chip magneto-optical (MO) devices.