Small molecules for integrated electro-optic modulators in nanophotonics

We discuss electrically poled small molecule assemblies that can serve as the active electro-optic material in nano-scale guided-wave circuits such as those of the silicon photonics platform. These monolithic organic materials can be assembled using physical vapor deposition in vacuum, making it possible to homogeneously fill nanometer-size integrated-optics structures. In addition, after deposition they can be electrically poled at higher temperatures to impart an orientational non-centrosymmetric order that remains stable at room temperature. As an example, using the "DDMEBT" molecule and corona poling delivers a material with the required high optical quality, an effective glass transition temperature of the order of ∼80°C, and an electro-optic coefficient of 20 pm/V. While this value is smaller than what can be achieved with poled polymers, it is comparable to LiNbO3, and the ability of small molecules to consistently and easily create a very homogenous filling in sub-100nm gaps is a unique advantage.