Investigation of novel optical and waveguide characteristics for an air-graphene-LiNbO₃system

The optical characteristics of a planar thin film waveguide system composed of air-graphene-LiNbO₃have been investigated. Monolayer or bilayer graphene of high quality are characterized by Raman spectroscopy, scanning electron microscopy and atomic force microscopy. The refractivity and reflectivity of the air-graphene-LiNbO₃system are measured experimentally and compared with those of a LiNbO₃waveguide by the prism coupling method. The reflectivity shows an overall decrease due to the lower transmittance for graphene on the LiNbO₃substrate. The refractivity increases significantly at the wavelength of 1540 nm, which may be attributed to the generation of graphene surface plasmons excited by infrared radiation. A shaped air-graphene-LiNbO₃waveguide is designed and simulated by Mode Solutions. The distribution of an optical field is performed and analyzed. The preparation of the proposed air-graphene-LiNbO₃structure incorporates the commonly used chemical vapor deposition and thin film transfer techniques, and is compatible with existing optoelectronic integration processes, which can be employed for building various optical integrated devices.