L.E. Johnson, D.L. Elder, H. Xu, L.R. Dalton, B.H. Robinson
Nonlinear Materials Corporation,
United States
Keywords: electro-optics, nonlinear optics, optical computing, materials design
Summary:
Computing and telecommunications are presently undergoing a massive transformation. Semiconductor circuit density (Moore’s law) is approaching physical limits, computing is consuming a rapidly growing fraction of the world’s electricity supply (predicted at 20% by 2025), and systems are becoming far more distributed (cloud computing), driving needs for high-speed, power-efficient components and connections at many different length scales. Interconnect needs range from connecting modules in CPU/GPU cores to long-distance optical networks. 5G telecom buildout is also driving a need for electronically steerable antenna systems capable of high frequency (30GHz-THz) operation. Optical and electro-optic technologies provide a high-speed, low-power solution to this problem. Cost-efficient implementation requires components at similar scales to electronic components and materials that can be integrated with conventional silicon CMOS technologies. Organic materials have previously been considered for high-speed electro-optic technologies due to exceptional electro-optic activity and THz intrinsic bandwidth, but were limited by the need for polymer binders, high optical loss, and limited device lifetimes. Hybrid device architectures, such as plasmonic-organic hybrid (POH) and silicon-organic hybrid (SOH) photonics systems present a promising approach that leverages the best aspects of organic electro-optic (OEO) materials and conventional semiconductor manufacturing processes. The refractive index of the organic layer in hybrid devices is incredibly sensitive to electric fields ( > 10X the electro-optic response of standard EO material lithium niobate), enabling signal detection and modulation within micro/nano-scale devices. Integration with silicon or plasmonic systems provides a platform for deployment of standard nanofabrication techniques and integration with electronics. Plasmonic components can further concentrate electric fields into the EO material, enabling smaller and more sensitive devices. Smaller device sizes also minimize issues with optical loss in the organic layer, allowing use of materials with stronger EO activity than in bulk devices. Research milestones realized using previous generation materials include > 1 THz bandwidth in antenna applications, > 170 GHz bandwidth in modulator applications, power consumption on the order of 1 fJ/bit, and device footprints < 10 μm2. As hybrid systems have different design constraints than bulk polymer devices, we have applied a variety of theoretical and computational tools to develop the next generation of electro-optic materials, intended to be deployed within these device architectures. We have designed and synthesized novel OEO materials with high glass transition temperatures that have been demonstrated in hybrid devices developed by academic partners, as well as designing and synthesizing a new generation of OEO materials with large refractive indices and exceptional hyperpolarizabilities, potentially enabling realization of electro-optic activities > 1000 pm/V and device voltage-length parameters of < 10 V-μm.