Electro-optic effect in epsilon-near-zero organic thin films

Third-order nonlinear optical response is shown to be enhanced near epsilon near zero (ENZ) spectral position. Regarding the materials exhibiting ENZ property, examples are reported such as hyperbolic metamaterial, inorganic oxides, nitrides, and organic monolithic hyperbolic thin film. By adopting series of organic thin films possessing ENZ property, we investigated second-order nonlinear optical process of electro-optic effect. When organic films are prepared in the order of several tens of nanometers thickness, a symmetry breaking takes place at the interface of organic thin film and substrate, allowing for second-order nonlinear optical responses of second harmonic generation and electro-optic (EO) effect. The presence of epsilon near pole (ENP) leads to an enhanced EO effect. The experimental results showed that the EO response is strongly enhanced in the spectral region of ENP associated with the existence of ENZ.