Abstract

Active modulation of light with large optical bandwidths (~100 nm [1]) is required in photonic devices, such as modulators for fiber communications [1] and saturable absorbers for ultrafast pulse generation [2,3]. Present modulators use expensive materials, (e.g. LiNbO₃ [4], III-V semiconductors [5], and Ge on silicon-on-insulator (SOI) [6]), and are limited by narrowband operation (~20 nm for quantum-confined Stark effect devices [7], or <0.1 nm for resonators [8]), or high loss (~80% in Si Mach-Zehnder modulators [9]). Single layer graphene (SLG) can be transferred and integrated on a variety of waveguide systems (e.g. a-Si, Si₃N₄) while offering a full-band operation [10]. In all-fiber platforms, including ultrafast lasers [2,3], high coupling losses (~60% from fiber to SOI waveguide [6]) are driving development of fiber-based modulators. Ref. 3 reported an electrically controllable all-fiber optical modulator with a SLG transistor on a side-polished fiber. However, its gating speed was limited to~300 Hz [11] due to the low mobility of the ionic liquid used for gating. Here, we report a graphene-microfiber modulator by integrating a microfiber onto a graphene (SLG plated) capacitor (GC). By varying the microfiber size and length we control the light interaction with the biased SLG plates. This can be used for active control of ultrafast laser working in continuous wave, Q-switching and mode-locking operations.

© 2017 IEEE