Title: New paradigms in materials and devices for hybrid electro-optics and optical rectification
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. more »« less
Hammond, Scott R.; O'Malley, Kevin M.; Xu, Huajun; Elder, Delwin L.; Johnson, Lewis E.(
, 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.
Johnson, Lewis E.; Elder, Delwin L.; Benight, Stephanie J.; Tillack, Andreas F.; Hammond, Scott R.; Heni, Wolfgang; Dalton, Larry R.; Robinson, Bruce H.(
, Physical Chemistry of Semiconductor Materials and Interfaces XX)
Congreve, Daniel; Nielsen, Christian; Musser, Andrew J.; Baran, Derya
(Ed.)
Hybrid organic electro-optic (OEO) devices 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 exceptional electro-optic switching 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. However, optimization of device performance requires both understanding and improving the degree to which chromophores can be acentrically ordered near a metal or semiconductor interface. Applying bulk and/or isotropic models of OEO materials to nanophotonic device architectures often lead to overly optimistic translation of materials performance to device performance. Prior work has identified influences of high centrosymmetric order (birefringence), altered relations between acentric and centrosymmetric order (dimensionality), and surface electrostatics on chromophore ordering. We combine these models into a representation that can be used to understand the influences of these phenomena on device performance, how some prior OEO materials exhibited unusually high performance under confinement, how ordering close to surfaces may be improved, and implications for future electro-optic device design.
Xu, Huajun; Johnson, Lewis E.; de Coene, Yovan; Elder, Delwin L.; Hammond, Scott. R.; Clays, Koen; Dalton, Larry R.; Robinson, Bruce H.(
, 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.
BACKGROUND Electromagnetic (EM) waves underpin modern society in profound ways. They are used to carry information, enabling broadcast radio and television, mobile telecommunications, and ubiquitous access to data networks through Wi-Fi and form the backbone of our modern broadband internet through optical fibers. In fundamental physics, EM waves serve as an invaluable tool to probe objects from cosmic to atomic scales. For example, the Laser Interferometer Gravitational-Wave Observatory and atomic clocks, which are some of the most precise human-made instruments in the world, rely on EM waves to reach unprecedented accuracies. This has motivated decades of research to develop coherent EM sources over broad spectral ranges with impressive results: Frequencies in the range of tens of gigahertz (radio and microwave regimes) can readily be generated by electronic oscillators. Resonant tunneling diodes enable the generation of millimeter (mm) and terahertz (THz) waves, which span from tens of gigahertz to a few terahertz. At even higher frequencies, up to the petahertz level, which are usually defined as optical frequencies, coherent waves can be generated by solid-state and gas lasers. However, these approaches often suffer from narrow spectral bandwidths, because they usually rely on well-defined energy states of specific materials, which results in a rather limited spectral coverage. To overcome this limitation, nonlinear frequency-mixing strategies have been developed. These approaches shift the complexity from the EM source to nonresonant-based material effects. Particularly in the optical regime, a wealth of materials exist that support effects that are suitable for frequency mixing. Over the past two decades, the idea of manipulating these materials to form guiding structures (waveguides) has provided improvements in efficiency, miniaturization, and production scale and cost and has been widely implemented for diverse applications. ADVANCES Lithium niobate, a crystal that was first grown in 1949, is a particularly attractive photonic material for frequency mixing because of its favorable material properties. Bulk lithium niobate crystals and weakly confining waveguides have been used for decades for accessing different parts of the EM spectrum, from gigahertz to petahertz frequencies. Now, this material is experiencing renewed interest owing to the commercial availability of thin-film lithium niobate (TFLN). This integrated photonic material platform enables tight mode confinement, which results in frequency-mixing efficiency improvements by orders of magnitude while at the same time offering additional degrees of freedom for engineering the optical properties by using approaches such as dispersion engineering. Importantly, the large refractive index contrast of TFLN enables, for the first time, the realization of lithium niobate–based photonic integrated circuits on a wafer scale. OUTLOOK The broad spectral coverage, ultralow power requirements, and flexibilities of lithium niobate photonics in EM wave generation provides a large toolset to explore new device functionalities. Furthermore, the adoption of lithium niobate–integrated photonics in foundries is a promising approach to miniaturize essential bench-top optical systems using wafer scale production. Heterogeneous integration of active materials with lithium niobate has the potential to create integrated photonic circuits with rich functionalities. Applications such as high-speed communications, scalable quantum computing, artificial intelligence and neuromorphic computing, and compact optical clocks for satellites and precision sensing are expected to particularly benefit from these advances and provide a wealth of opportunities for commercial exploration. Also, bulk crystals and weakly confining waveguides in lithium niobate are expected to keep playing a crucial role in the near future because of their advantages in high-power and loss-sensitive quantum optics applications. As such, lithium niobate photonics holds great promise for unlocking the EM spectrum and reshaping information technologies for our society in the future. Lithium niobate spectral coverage. The EM spectral range and processes for generating EM frequencies when using lithium niobate (LN) for frequency mixing. AO, acousto-optic; AOM, acousto-optic modulation; χ (2) , second-order nonlinearity; χ (3) , third-order nonlinearity; EO, electro-optic; EOM, electro-optic modulation; HHG, high-harmonic generation; IR, infrared; OFC, optical frequency comb; OPO, optical paramedic oscillator; OR, optical rectification; SCG, supercontinuum generation; SHG, second-harmonic generation; UV, ultraviolet.
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.(
, Advanced Materials)
Abstract
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/Ep, Epis 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.
Johnson, Lewis E., Elder, Delwin L., Xu, Huajun, Hammond, Scott W., Benight, Stephanie J., O'Malley, Kevin, Robinson, Bruce H., and Dalton, Larry R. New paradigms in materials and devices for hybrid electro-optics and optical rectification. Retrieved from https://par.nsf.gov/biblio/10378642. Molecular and Nano Machines IV . Web. doi: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. New paradigms in materials and devices for hybrid electro-optics and optical rectification. Molecular and Nano Machines IV, (). Retrieved from https://par.nsf.gov/biblio/10378642. 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., and Dalton, Larry R.
"New paradigms in materials and devices for hybrid electro-optics and optical rectification". Molecular and Nano Machines IV (). Country unknown/Code not available. https://doi.org/10.1117/12.2595638.https://par.nsf.gov/biblio/10378642.
@article{osti_10378642,
place = {Country unknown/Code not available},
title = {New paradigms in materials and devices for hybrid electro-optics and optical rectification},
url = {https://par.nsf.gov/biblio/10378642},
DOI = {10.1117/12.2595638},
abstractNote = {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.},
journal = {Molecular and Nano Machines IV},
author = {Johnson, Lewis E. and Elder, Delwin L. and Xu, Huajun and Hammond, Scott W. and Benight, Stephanie J. and O'Malley, Kevin and Robinson, Bruce H. and Dalton, Larry R.},
editor = {Sekkat, Zouheir and Omatsu, Takashige}
}
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