Documentation

Technical documentation and specifics 

Published Date: January 13, 2020

Ultrahigh Electro-Optic Coefficients, High Index of Refraction, and Long-Term Stability from Diels–Alder Cross-Linkable Binary Molecular Glasses

Abstract: The development of organic electro-optic (EO) materials that concurrently possess a high electro-optic coefficient (r33), high index of refraction, and long-term or high-temperature stability of chromophore alignment has been a crucial goal. To address this challenge, we developed a crosslinkable EO system consisting of two chromophores, HLD1 and HLD2, which can be electric field poled and then thermally crosslinked in situ to form a stable EO material. This approach avoids the necessity for nonlinear optically inactive materials such as polymers or small molecule cross-linkers, thus resulting in high chromophore density (>5 × 1020 molecules/cm3) and high index of refraction (n = 1.89 at 1310 nm) for HLD1/HLD2. Different ratios of HLD1 and HLD2 were evaluated to optimize poling efficiency and thermal stability of the poling-induced order. With 2:1 HLD1/HLD2 (wt/wt), a maximum r33 of 290 ± 30 pm/V was achieved in a cross-linked film. Thermal stability tests showed that after heating to 85 °C for 500 h, greater than 99% of the initial r33 value was maintained. This combination of large EO activity, high index of refraction, and long-term alignment stability is an important breakthrough in EO materials. HLD1/HLD2 can also be poled without the subsequent cross-linking step, and even larger maximum r33 (460 ± 30 pm/V) and n3r33 figure of merit (3100 ± 200 pm/V) were achieved. Hyperpolarizabilities of HLD and control molecules were analyzed by hyper-Rayleigh scattering and computational modeling with good agreement, and they help explain the high acentric order achieved during poling.

Citations:

Published Date: June 1, 2020

A monolithic bipolar CMOS electronic–plasmonic high-speed transmitter

Abstract: To address the challenge of increasing data rates, next-generation optical communication networks will require the co-integration of electronics and photonics. Heterogeneous integration of these technologies has shown promise, but will eventually become bandwidth-limited. Faster monolithic approaches will therefore be needed, but monolithic approaches using complementary metal–oxide–semiconductor (CMOS) electronics and silicon photonics are typically limited by their underlying electronic or photonic technologies. Here, we report a monolithically integrated electro-optical transmitter that can achieve symbol rates beyond 100 GBd. Our approach combines advanced bipolar CMOS with silicon plasmonics, and addresses key challenges in monolithic integration through co-design of the electronic and plasmonic layers, including thermal design, packaging and a nonlinear organic electro-optic material. To illustrate the potential of our technology, we develop two modulator concepts—an ultra-compact plasmonic modulator and a silicon-plasmonic modulator with photonic routing—both directly processed onto the bipolar CMOS electronics.

Citations:

  • Koch, U.; Uhl, C.; Hettrich, H.; Fedoryshyn, Y.; Hoessbacher, C.; Heni, W.; Baeuerle, B.; Bitachon, B. I.; Josten, A.; Ayata, M.; Xu, H.; Elder, D. L.; Dalton, L. R.; Mentovich, E.; Bakopoulos, P.; Lischke, S.; Krüger, A.; Zimmermann, L.; Tsiokos, D.; Pleros, N.; Möller, M.; Leuthold, J.. Nature Electronics. 2020, 3, 338–345. Doi: https://doi.org/10.1038/s41928-020-0417-9

Published Date: June 20, 2014

Benzocyclobutene barrier layer for suppressing conductance in nonlinear optical devices during electric field poling

Abstract: We measured the electro-optic (EO) coefficients (r33) of thin-film devices made from several monolithic, high number density organic EO chromophores with and without additional charge barrier layers. We found that a cross-linkable benzocyclobutene layer was very effective in suppressing unwanted, leakage current, keeping the effective poling voltage nearly identical to the applied voltage. This barrier layer proved to be superior to a titanium dioxide (TiO2) barrier layer. The suppression of the leakage current in combination with a new chromophore enabled the construction of EO devices that had r33 values in the range of 400–500 pm V−1 with poling fields ≥ 85 V μm−1.

Citations:

  • Jin, W.; Johnston, P. V.; Elder, D. L.; Tillack, A. F.; Olbricht, B. C.; Song, J.; Reid, P. J.; Xu, R.; Robinson, B. H.; Dalton, L. R.. Applied Physics Letters. 2014, 104, 243304. Doi: https://doi.org/10.1063/1.4884829

Published Date: March 18, 2016

Structure–function relationship exploration for enhanced thermal stability and electro-optic activity in monolithic organic NLO chromophores

Abstract: We have developed a series of novel monolithic materials based on molecules previously explored as dopants in guest–host systems to study intrinsic structure–function relationships in organic electro-optic (EO) materials. In a library of EO molecules with varied bridge segments, molecular modification of the donor with bis(tert-butyldiphenylsilyl) groups led to improvement in formation of amorphous films and led to enhanced poling efficiency. Further modification to include a carbazole site-isolation group on the bridge effectively reduced intermolecular dipole–dipole interactions, led to a material with poling efficiency of approximately 3 (nm V−1)2, and an increased glass transition temperature to 20–40 °C higher than similar reported monolithic materials. This level of thermal stability is comparable to common guest/host systems, which incorporated poly(methyl methacrylate) (PMMA) as the host. Our research showed that π-bridge length and type impacted first molecular hyperpolarizability β of a chromophore, which is accordingly reflected in the EO response. These findings further promote the utility of monolithic materials for their increased EO behavior and improved thermal stability, making this material system a competitor of guest–host systems in commercial applications.

Citations:

  • Jin, W.; Johnston, P. V.; Elder, D. L.; Manner, K. T.; Garrett, K. E.; Kaminsky, W.; Xu, R.; Robinson, B. H.; Dalton, L. R.. Journal of Materials Chemistry C. 2016, 4, 3119-3124. Doi: https://doi.org/10.1039/C6TC00358C

Published Date: June 7, 2018

Ultra-high electro-optic activity demonstrated in a silicon-organic hybrid modulator

Abstract: Efficient electro-optic (EO) modulators crucially rely on advanced materials that exhibit strong electro-optic activity and that can be integrated into high-speed and efficient phase shifter structures. In this paper, we demonstrate ultra-high in-device EO figures of merit of up to n3r33=2300  pm/V achieved in a silicon-organic hybrid (SOH) Mach–Zehnder modulator (MZM) using the EO chromophore JRD1. This is the highest material-related in-device EO figure of merit hitherto achieved in a high-speed modulator at any operating wavelength. The π-voltage of the 1.5-mm-long device amounts to 210 mV, leading to a voltage-length product of UπL=320  Vμm—the lowest value reported for MZM that are based on low-loss dielectric waveguides. The viability of the devices is demonstrated by generating high-quality on-off-keying signals at 40 Gbit/s with Q factors in excess of 8 at a drive voltage as low as 140  mVpp. We expect that efficient high-speed EO modulators will not only have a major impact in the field of optical communications, but will also open new avenues towards ultrafast photonic-electronic signal processing.

Citations:

  • Kieninger, C.; Kutuvantavida, Y.; Wolf, S.; Zwichel, H.; Blaicher, M.; Kemal, J.; Elder, D. L.; Lauermann, M.; Dalton, L. R.; Freude, W.; Randel, S.; Koos, C.. Optica. 2018, 5 (6) , 739-748. Doi: https://doi.org/10.1364/OPTICA.5.000739