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Coherent optical communications provides the largest data transmission capacity with the highest spectral efficiency and therefore has a remarkable potential to satisfy today’s ever-growing bandwidth demands. It relies on so-called in-phase/quadrature (IQ) electro-optic modulators that encode information on both the amplitude and the phase of light. Ideally, such IQ modulators should offer energy-efficient operation and a most compact footprint, which would allow high-density integration and high spatial parallelism. Here, we present compact IQ modulators with an active section occupying a footprint of 4 × 25 µm × 3 µm, fabricated on the silicon platform and operated with sub-1-V driving electronics. The devices exhibit low electrical energy consumptions of only 0.07 fJ bit −1 at 50 Gbit s −1 , 0.3 fJ bit −1 at 200 Gbit s −1 , and 2 fJ bit −1 at 400 Gbit s −1 . Such IQ modulators may pave the way for application of IQ modulators in long-haul and short-haul communications alike.

Integrated ferroelectric plasmonic modulators featuring large bandwidths, broad optical operation range, resilience to high temperature and ultracompact footprint are introduced. Measurements show a modulation bandwidth of 70 GHz and a temperature stability up to 250°C. Mach-Zehnder interferometer modulators with 10-µm-long phase shifters were operated at 116 Gbit/s PAM-4 and 72 Gbit/s NRZ. Wide and open eye diagrams with extinction ratios beyond 15 dB were found. The fast and robust devices are apt to an employment in industrial environments.

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The perovskite compounds La 0.33 Sr 0.67 Cr 1−x−yFe x Ru y O 3−δ (LSCrFeRu, x = 0.62, 0.57, and 0.47; y = 0.05, 0.14, and 0.2, respectively) were synthesized and assessed as a new type of solid oxide fuel cell (SOFC) anode in composite with Gd 0.1 Ce 0.9 O 2-β (GDC) in La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-ε / La 0.4 Ce 0.6 O 2 bilayer electrolyte-supported cells. By comparing anode polarization resistance R P,A values for the LSCrFeRu compounds to the either exclusively Fe-or Ru-substituted (La,Sr)CrO 3−δ perovskites, the present results demonstrate that the two substituent cations work synergistically to provide further reduction in R P,A from 0.290 Ω·cm 2 for La 0.33 Sr 0.67 Cr 0.33 -F e 0 . 6 7 O 3 − δ ( L S C r F e ) a n d 0 . 2 3 5 Ω · c m 2 f o r La 0.8 Sr 0.2 Cr 0.8 Ru 0.2 O 3−δ (LSCrRu) to 0.195 Ω·cm 2 for LSCrFeRu (all measured in humidified hydrogen at 800°C). These impedance results also strongly suggest that hydrogen dissociative adsorption was the rate-limiting step in the hydrogen oxidation reaction sequence for LSCrFe anodes at some of the pH 2 and temperatures measured. However, the formation of Ru nanoparticles on LSCrFeRu and LSCrRu surfaces, observed by scanning and transmission electron microscopy, appears to promote hydrogen dissociation. Substituting even small amounts of Ru into (La,Sr)(Cr,Fe)O 3−δ perovskites is thus sufficient to make hydrogen electrochemical oxidation the rate-limiting step, resulting in anodes with significantly reduced R P,A .