Optical Isolation Based on Nonreciprocal Micro-Ring Resonator

We propose a nonreciprocal waveguide with different wavevectors for forward and backward propagations. Utilizing this nonreciprocal waveguide, we further compose a nonreciprocal micro-ring resonator, which possesses different phase shifts for clockwise and anticlockwise circulatings. Using this nonreciprocal resonator, more than 20 dB optical isolation can be achieved. This work demonstrates that on-chip optical isolations can be accomplished with simple nonreciprocal resonator components, which can show promising applications for integrated optoelectronic systems.