▎ 摘　　要

Optically controlled phase shifters are desirable for optical communication, sensors, and signal processing due to their simple implementation and low cost. We propose an all-fiber phase shifter assisted by graphene's photothermal effect. In a graphene-coated microfiber, graphene's ohmic heating promises efficient fiber index change and phase shift via the thermo-optic effect. On a fabricated device with a length of 5 mm, we obtain a phase shift exceeding 21 pi with a nearly linear slope of 0.091 pi/mW (0.192 pi/mW) when pumped by 980 nm (1540 nm) light, which enables all-optical switching with an extinction ratio of 20 dB and a rise (fall) time of 9.1 ms (3.2 ms) following the 10%-90% rule. This graphene-assisted index change and phase shifter featured with all-in-fiber, low power requirement, and ease of fabrication may open the door for graphene's realistic applications in all-optical signal processing. (C) 2015 Optical Society of America