Graphene decorated twin-core fiber Michelson interferometer for all-optical phase shifter and switch

We investigated an all-optical phase shifter and switch based on a graphene decorated side-polished twin-core fiber (TCF) Michelson interferometer (MI). The MI was fabricated by tapering the splicing point between the TCF and single-mode fiber. The flat surface of exposed polished core in the TCF was coated with monolayer graphene. A 980 nm pump laser is used to produce a photothermal effect. The graphene’s ohmic heating changes the effective refractive index of the exposed core, resulting in the phase shift of the MI. The MI with a polished length of 5 mm has a significant modulation phase shift with a nearly linear slope of 0.0102 π / m W near the wavelength of 1550 nm and can obtain an extinction ratio of 7 dB for optical switching with a rise (fall) time of 55.8 ms (15.5 ms). The high-density integration and all-optical control enable the proposed device to have great potential in the miniaturization of optical devices and all-optical signal processing.