On-chip all-optical nonreciprocal device for short-pulse isolator based on free carrier dispersion effect

Abstract

Chip-scale nonreciprocal devices, including isolators and circulators, are indispensable in the application of optical communications, all-optical signal processing and LiDAR, holding the advantages of small-size, mass-production and portability. Approaches that involve the integration of magnetooptical materials and spatiotemporal modulation have been demonstrated, yet with a high insertionloss or requiring additional bias. Here, we proposed a novel all-optical, passive, bias-free nonreciprocal silicon chip based on free carrier dispersion effect for short pulse application scenarios. An asymmetric and scalable silicon resonator is fabricated using a standard CMOS technique with the footprint of only 100 μm2, showing a nonreciprocal transmission ratio of 25 dB, with an insertion loss as low as 1.65 dB under CW laser conditions. A clear blue shift with 0.03 nm is observed under 1 ns pulse with the incident operated peak power ranging from 13 mW to 105 mW. Furthermore, we apply it for chip-based isolator with a high isolation ratio and LiDAR with a spatial resolution down to 15 cm. Such short-pulse suitable nonreciprocal devices can greatly enhance the spatial resolution of LiDAR or increase the on-chip integration density since the reflecting-safe distance is greatly shortened. Therefore, this work provides a building block for high-performance chip-scale LiDAR and high integration density optical processing and communication devices.