Thermo-optic coefficient of chemical vapor deposited graphene multilayers

Observation of strong inelastic light-matter interaction and large thermal conductivity of novel two-dimensional graphene has invigorated the present research. Herein, the thermo-optic coefficient of graphene multilayers is obtained from their nonlinear refraction coefficients calculated from Z-scan experiment in closed aperture geometry. The refractive optical nonlinearity was obtained employing a continuous wave He-Ne laser and occurs due to thermal lensing effect. The graphene multilayers behave as the diverging (concave) lens giving rise to self-defocusing effect leading to negative sign of refractive nonlinearity. Accordingly, a large negative thermo-optic coefficient (-2.43×10-3 K-1) inferred for the graphene multilayers suggests its utility for thermo-optic device applications. Keywords: Graphene, Optical Nonlinearity, Thermal lens, Self-defocusing, Thermo-optic coefficients