▎ 摘　　要

We propose a novel, to the best of our knowledge, tunable delay line based on high-performance three-dimensional (3-D) switches driven by graphene heaters. The 3-D switches, which are constructed with a vertical directional coupler (VDC), provide continuous tuning functionality of the proposed delay line by tuning the coupling ratio of the VDC. The use of the graphene electrode by placing it in direct contact with the upper waveguide core, combined with the air slots formed on both sides of the waveguides, causes the switch to have a quite low power consumption of 3.6 mW. Our designed device, which has a footprint of 20 mm x 6.8 mm, is capable of providing a continuous tunable delay from 0 to 150 ps with minimum operating bandwidth of >3.34 GHz, from 0 to 100 ps with minimum operating bandwidth of >5 GHz, and from 0 to 50 ps with minimum operating bandwidth of >10 GHz. The cross talk for different delay cases is less than -21.6 dB over the whole C-band and less than -45.2 dB at 1550 nm. (C) 2021 Optical Society of America