On‐Chip All‐Optical Nonreciprocal Device for Short‐Pulse Isolator Based on Free Carrier Dispersion Effect

Abstract Chip‐scale nonreciprocal devices such as isolators and circulators are essential for optical communications, all‐optical signal processing, and LiDAR systems, owing to their compact footprint, manufacturability, and portability. Devices capable of handling short optical pulses are particularly desirable, as they enable reduced energy consumption, higher processing speed and improved ranging resolution and accuracy. In this work, a novel all‐optical, passive, bias‐free nonreciprocal silicon chip leveraging the high‐speed free carrier dispersion effect is introduced, pioneering new prospects of short‐pulse nonreciprocal silicon devices. An asymmetric and scalable silicon resonator is fabricated using standard CMOS techniques with a footprint of merely 100 µm 2 , achieving a nonreciprocal transmission ratio of 25 dB and an insertion loss as low as 1.65 dB. A noticeable blueshift of 0.05 nm is observed under a 1 ns pulse with incident peak power ranging from 9.3 to 234.4 mW. Furthermore, it is applied as a chip‐based isolator in LiDAR, exhibiting isolation and measuring consistency. This nonreciprocal device, optimized for short pulses, can significantly enhance the spatial resolution of LiDAR or increase on‐chip integration density by reducing the reflecting‐safe distance. Consequently, this work lays the foundation for high‐performance chip‐scale LiDAR and high‐density optical processing and communication devices.