Indexed on: 22 Dec '17Published on: 22 Dec '17Published in: ACS Applied Materials & Interfaces
We propose a graphene-based optical modulator and comprehensively investigate its photonic characteristics by electrically controlling the device with an ion-gel top-gate dielectric. The density of the electrically driven charge-carriers in the ion-gel gate dielectric plays a key role in tuning the optical output power of the device. The charge density at the ion-gel-graphene interface is tuned electrically, and the chemical potential of graphene is then changed to control its light absorption strength. The optical behavior by the ion-gel gate dielectric exhibits a large hysteresis which originates from the inherent nature of the ionic gel and the graphene-ion-gel interface, slow polarization response time of ions. The photonic device is applicable to both TE- and TM-polarized light waves, covering two entire optical communication bands, the O-band (1.26-1.36 μm) and C-band (1.52-1.565 μm). The experimental results are in good agreement with theoretically simulated predictions. The temporal behavior of the ion-gel-graphene-integrated optical modulator reveals a long-term modulation state due to the relatively low mobility of the ions in the ion-gel solution and formation of the electric double layer in the graphene-ion-gel interface. Fast dynamic recovery is observed by applying an opposite voltage gate pulse. This study paves the way to understanding the operational principles and future applications of ion-gel-gated graphene optical devices in photonics.