Manipulation of Nonlinear Optical Properties of Graphene Bonded Fiber Devices by Thermally Engineering Fermi-Dirac Distribution

Graphene's atomic thickness, gapless Dirac-Fermionic band structure, and large thermal conductivity make it a promising element for applications in photonic integrated devices. Importantly, actively tunable graphene-waveguide-integrated optoelectronic devices can potentially be utilized for the realization of reconfigurable photonic systems. Since electrical device control is always preferred, researchers have previously demonstrated gate-variable graphene devices; however, electrical control remains challenging, particularly in all-fiber systems because of the required complicated configuration and fabrication techniques along with additional signal loss. Here, a graphene-fiber-integrated platform is proposed and the manipulation of its nonlinear optical properties is demonstrated by engineering the Fermi-Dirac distribution of graphene based on a convenient electric heating method. For the first time, it is experimentally shown that the nonlinear optical absorption of graphene is correlated to temperature via the thermal relaxation process. In the experiments, the modulation depth variation exceeds 60%. The configuration is simple, cost-effective, and can be readily extended to other 2D materials. It is believed that this work can contribute to building miniature and compact graphene-fiber-integrated devices for actively tunable multifunctional applications.