L.E. Johnson, D.L. Elder, S.R. Hammond, K.M. O’Malley
Keywords: electro-optic modulation, integrated photonics, hybrid photonics, silicon photonics, organic materials, datacom
Summary:Ubiquitous computing requires seamless, efficient, high-bandwidth communications across different length scales and network topologies. As present and near-future compute needs, particularly in AI/ML, strain datacenter network capacity and network equipment power requirements, a scalable path for improvement of bandwidth per watt is needed. A key requirement in providing this bandwidth is efficient electrical to optical signal conversion, operating at CMOS-level drive voltages. This would not only enable further scaling of datacenter network capacity, but enable closer integration of electronics with photonics and use of efficient photonic connections on shorter length scales. It would also enable integration of new computing modalities, such as optical neural networks that could substantially increase the performance of ML operations while reducing their energy use, and quantum computing—whether connecting superconducting Qubits or in photonic quantum computing. Organic materials have previously been considered for high-speed electro-optic modulation 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 organic electro-optic (EO) modulation technology, combining organic electro-optic (OEO) materials with conventional semiconductor (e.g. silicon photonics) or dielectric (e.g. SiN) photonics platforms, adds the exceptional Pockels effect modulation capabilities of these materials to the underlying semiconductor platforms in device architectures that maximize their performance through high optical mode confinement. Hybrid organic devices can achieve modulation efficiencies (VπL) 10-100x superior to typical silicon photonic modulators and thin-film lithium niobate modulators. NLM Photonics’ crosslinkable organic glass technology enables a combination of exceptional EO efficiency (up to 30x that of lithium niobate) and long-term thermal stability at temperatures up to 120°C for meeting the demanding requirements for datacenter applications. Hybrid EO capabilities can be added to photonics platforms using standard nanofabrication techniques and solution processing, with commercial demonstrations to date on silicon photonics (SOH) and plasmonic (POH) platforms. Along with our partners, we have integrated electro-optic materials with unprecedented performance in hybrid devices and developed materials with high stability combined with ultra-high electro-optic activity, optimized the processing of these materials, performed key studies related to environmental stability, mitigating optical loss, packaging needs, and back-end process flows, on the path to scaling hybrid OEO technology in integrated photonic devices.