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1. Organic electro-optic materials combining extraordinary nonlinearity with exceptional stability to enable commercial applications

   https://doi.org/10.1117/12.2622099  

   Hammond, Scott R. ; O'Malley, Kevin M. ; Xu, Huajun ; Elder, Delwin L. ; Johnson, Lewis E. ( March 2022 , Organic Photonic Materials and Devices XXIV)

   Rau, Ileana ; Sugihara, Okihiro ; Shensky, William M. (Ed.)

   Hybrid organic electro-optic (OEO) modulators consist of a layer of ordered organic chromophores confined between layers of metals or semiconductors, enabling optical fields to be tightly confined within the OEO material. The combination of tight confinement with the high electro-optic (EO) performance of state-of-the-art OEO materials enables extraordinary EO modulation performance in silicon-organic hybrid (SOH) and plasmonic-organic hybrid (POH) device architectures. Recent records in POH devices include bandwidths >500 GHz and energy efficiency <100 aJ/bit. To enable commercial applications of these materials and devices, however, they must withstand demanding thermal and environmental conditions, both during manufacture and operation. To address these concerns, we examined the long-term thermal and environmental shelf storage stability of state-of-the-art commercial and developmental OEO materials under a variety of conditions relevant to Telecordia GR-468-CORE standards. We examined the shelf storage of poled OEO materials under a nitrogen atmosphere at a range of temperatures from 85 ̊C up to 150 ̊C to understand the kinetics of the thermally activated de-poling of the OEO materials. We also examined the shelf storage of OEO materials under a variety of atmospheres, including the aggressive 85 ̊C and 85% relative humidity damp heat condition, to understand the relative sensitivities of the materials to water and oxygen at different temperatures. We analyze the results of these studies and discuss their implications for commercial application of these materials and devices, including manufacturing, encapsulation requirements, and expected operational lifetimes. 

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2. New paradigms in materials and devices for hybrid electro-optics and optical rectification

   https://doi.org/10.1117/12.2595638  

   Johnson, Lewis E. ; Elder, Delwin L. ; Xu, Huajun ; Hammond, Scott W. ; Benight, Stephanie J. ; O'Malley, Kevin ; Robinson, Bruce H. ; Dalton, Larry R. ( August 2021 , Molecular and Nano Machines IV)

   Sekkat, Zouheir ; Omatsu, Takashige (Ed.)

   We review recent transformative advances in materials design, synthesis, and processing as well as device engineering for the utilization of organic materials in hybrid electro-optic (EO) and optical rectification (OR) technologies relevant to telecommunications, sensing, and computing. End-to-end (from molecules to systems) modeling methods utilizing multi-scale computation and theory permit prediction of the performance of novel materials in nanoscale device architectures including those involving plasmonic phenomena and architectures in which interfacial effects play a dominant role. Both EO and OR phenomenon require acentric organization of constituent active molecules. The incumbent methodology for achieving such organization is electric field poling, where chromophore shape, dipole moment, and conformational flexibility play dominant roles. Optimized chromophore design and control of the poling process has already led to record-setting advances in electro-optic performance, e.g., voltage-length performance of < 50 volt-micrometer, bandwidths > 500 GHz, and energy efficiency < 70 attojoule/bit. They have also led to increased thermal stability, low insertion loss and high signal quality (BER and SFDR). However, the limits of poling in the smallest nanophotonic devices—in which extraordinary optical field densities can be achieved—has stimulated development of alternatives based on covalent coupling of modern high-performance chromophores into ordered nanostructures. Covalent coupling enables higher performance, greater scalability, and greater stability and is especially suited for the latest nanoscale architectures. Recent developments in materials also facilitate a new technology—transparent photodetection based on optical rectification. OR does not involve electronic excitation, as is the case with conventional photodiodes, and as such represents a novel detection mechanism with a greatly reduced noise floor. OR already dominates at THz frequencies and recent advances will enable superior performance at GHz frequencies as well. 

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3. Electro‐Optic Activity in Excess of 1000 pm V −1 Achieved via Theory‐Guided Organic Chromophore Design

   https://doi.org/10.1002/adma.202104174  

   Xu, Huajun ; Elder, Delwin L. ; Johnson, Lewis E. ; de Coene, Yovan ; Hammond, Scott R. ; Vander Ghinst, Wouter ; Clays, Koen ; Dalton, Larry R. ; Robinson, Bruce H. ( September 2021 , Advanced Materials)

   High performance organic electro‐optic (OEO) materials enable ultrahigh bandwidth, small footprint, and extremely low drive voltage in silicon‐organic hybrid and plasmonic‐organic hybrid photonic devices. However, practical OEO materials under device‐relevant conditions are generally limited to performance of≈300 pm V⁻¹(10× the EO response of lithium niobate). By means of theory‐guided design, a new series of OEO chromophores is demonstrated, based on strong bis(4‐dialkylaminophenyl)phenylamino electron donating groups, capable of EO coefficients (r₃₃) in excess of 1000 pm V⁻¹. Density functional theory modeling and hyper‐Rayleigh scattering measurements are performed and confirm the large improvement in hyperpolarizability due to the stronger donor. The EO performance of the exemplar chromophore in the series, BAY1, is evaluated neat and at various concentrations in polymer host and shows a nearly linear increase inr₃₃and poling efficiency (r₃₃/E_p, E_pis poling field) with increasing chromophore concentration. 25 wt% BAY1/polymer composite shows a higher poling efficiency (3.9 ±0.1 nm²V⁻²) than state‐of‐the‐art neat chromophores. Using a high‐ε charge blocking layer with BAY1, a record‐highr₃₃(1100 ±100 pm V⁻¹) and poling efficiency (17.8 ±0.8 nm²V⁻²) at 1310 nm are achieved. This is the first reported OEO material with electro‐optic response larger than thin‐film barium titanate.

    

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4. Bis(4-dialkylaminophenyl)heteroarylamino donor chromophores exhibiting exceptional hyperpolarizabilities

   https://doi.org/10.1039/d0tc05700b  

   Xu, Huajun ; Johnson, Lewis E. ; de Coene, Yovan ; Elder, Delwin L. ; Hammond, Scott. R. ; Clays, Koen ; Dalton, Larry R. ; Robinson, Bruce H. ( March 2021 , Journal of Materials Chemistry C)

   Organic electro-optic (EO) materials incorporated into silicon-organic hybrid and plasmonic-organic hybrid devices have enabled new records in EO modulation performance. We report a new series of nonlinear optical chromophores engineered by theory-guided design, utilizing bis(4-dialkylaminophenyl)heteroarylamino donor moieties to greatly enhance molecular hyperpolarizabilities. Hyperpolarizabilities predicted using density functional theory were validated by hyper-Rayleigh scattering measurements, showing strong prediction/experiment agreement and >2-fold advancement in static hyperpolarizability over the best prior chromophores. Electric field poled thin films of these chromophores showed significantly enhanced EO coefficients ( r 33 ) and poling efficiencies ( r 33 / E p ) at low chromophore concentrations compared with state-of-the-art chromophores such as JRD1 . The highest performing blend, containing just 10 wt% of the novel chromophore BTP7 , showed a 12-fold enhancement in poling efficiency per unit concentration vs. JRD1 . Our results suggest that further improvement in chromophore hyperpolarizability is feasible without unacceptable tradeoffs with optical loss or stability. 

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5. Engineering Multi‐Scale Organization for Biotic and Organic Abiotic Electroactive Systems

   https://doi.org/10.1002/advs.202205381  

   Yao, Ze‐Fan ; Lundqvist, Emil ; Kuang, Yuyao ; Ardoña, Herdeline Ann M. ( January 2023 , Advanced Science)

   Multi‐scale organization of molecular and living components is one of the most critical parameters that regulate charge transport in electroactive systems—whether abiotic, biotic, or hybrid interfaces. In this article, an overview of the current state‐of‐the‐art for controlling molecular order, nanoscale assembly, microstructure domains, and macroscale architectures of electroactive organic interfaces used for biomedical applications is provided. Discussed herein are the leading strategies and challenges to date for engineering the multi‐scale organization of electroactive organic materials, including biomolecule‐based materials, synthetic conjugated molecules, polymers, and their biohybrid analogs. Importantly, this review provides a unique discussion on how the dependence of conduction phenomena on structural organization is observed for electroactive organic materials, as well as for their living counterparts in electrogenic tissues and biotic‐abiotic interfaces. Expansion of fabrication capabilities that enable higher resolution and throughput for the engineering of ordered, patterned, and architecture electroactive systems will significantly impact the future of bioelectronic technologies for medical devices, bioinspired harvesting platforms, and in vitro models of electroactive tissues. In summary, this article presents how ordering at multiple scales is important for modulating transport in both the electroactive organic, abiotic, and living components of bioelectronic systems.

    

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