Determination of complex refractive index of graphene waveguide by microfiber knot sensor

Abstract

In this paper, a novel method to sensing the complex refractive index (CRI) of graphene waveguide (GW) is demonstrated. Theoretical analysis and simulated results indicate the spectral properties of evanescent wave guided by microfiber would be modulated by the GW nearby. In experiment, evanescent waves with wavelength from 1510nm to 1590nm transimitting on the surface of the GW for a few centimeters, which are launched and collected by specially designed microfiber knot sensors (MFKSs). Repeated experiments and statistic results verifie that the CRI of the GW varies from 2.59-i2.66 to 2.51-i2.84 for 1510nm-1590nm band. Such an application of MFKS is suitable not only for the GW, but also for other thin films, which would be significant for the design and research of state-of-art optical devices.