Ultra-broadband on-chip power splitters for arbitrary ratios on silicon-on-insulator.

We propose and demonstrate on-chip power splitters based on adiabatic rib waveguide enabling arbitrary splitting ratios on a monolithic silicon photonic platform. The devices are elaborately engineered based on adiabatic directional couplers with a trapezoid-structure in the longitudinal direction in the mode evolution region. The measurement results indicate that the proposed devices can achieve over 150 nm bandwidth for arbitrary splitting ratios of 50%:50%, 70%:30% and 90%:10%.

X-Intersected Silicon Modulator of Well-Rounded Performance.

In silicon modulator design, implantation is always a key factor, significantly influencing the doping profile and carrier distribution. As waveguide doping is limited by the compact footprint of the modulator rib, three-dimensional complex optimization is a viable option to improve performance. This work proposes an X-intersected modulator based on two inversely slanted junctions using the effective 3D Monte Carlo method for junction generation.

Compact, ultrabroadband and temperature-insensitive arbitrary ratio power splitter based on adiabatic rib waveguides.

We propose a compact, ultrabroadband and temperature-insensitive adiabatic directional coupler based on rib silicon waveguide-enabling arbitrary splitting ratios. Simulation results show that the device can achieve arbitrary splitting ratios from 1400 to 1600 nm, equal to 50%:50%, 60%:40%, 70%:30%, 80%:20%, and 90%:10% for the fundamental transverse electric mode. The designed device has an excess loss of less than 0.

Silicon modulator based on omni junctions by effective 3D Monte-Carlo method.

3D doping structure has significant advantages in modulation efficiency and loss compared with 2D modulator doping profiles. However, to the best of our knowledge, previous work on 3D simulation methods for interdigitated doping designs applied simplified models, which prohibited complex 3D doping. In this work, innovative omni junctions, based on the effective 3D Monte-Carlo method, are believed to be the first proposed for high-performance modulators.

Broadband and CMOS compatible polarization splitter-rotator based on a bi-level taper.

A silicon-on-insulator polarization diversity scheme is proposed. Based on an asymmetrical evanescent coupler, a broadband and compact polarization splitter-rotator comprising mode conversion tapers and mode sorting asymmetric Y junctions is optimized with silicon dioxide upper cladding and a silicon nitride waveguide. The simulation results show mode conversion loss is less than 0.

Wafer-Scale and Full-Coverage Two-Dimensional Molecular Monolayers Strained by Solvent Surface Tension Balance.

Inspired by the outstanding properties discovered in two-dimensional materials, the bottom-up generation of molecular monolayers is becoming again extremely popular as a route to develop novel functional materials and devices with tailored characteristics and minimal materials consumption. However, achieving a full-coverage over a large-area still represents a grand challenge. Here we report a molecular self-assembly protocol at the water surface in which the monolayers are strained by a novel solvent surface tension balance (SSTB) instead of a physical film balance as in the conventional Langmuir-Blodgett (LB) method.

Compact, broadband, and low-loss silicon photonic arbitrary ratio power splitter using adiabatic taper.

The arbitrary ratio power splitter is widely used in photonic integrated circuits (PICs), for signal monitoring, power equalization, signal feedback, and so on. Here we designed a fabrication-tolerant, compact, broadband, and low-loss arbitrary ratio power splitter. The proposed arbitrary ratio power splitter was realized with an adiabatically tapered silicon rib waveguide with 70 nm shallow etches and an waveguide.

Compact multimode waveguide based temperature-insensitive Mach-Zehnder interferometer.

A novel multimode waveguide based Mach-Zehnder interferometer (MZI) is demonstrated on an SOI platform with the properties of compact footprint and temperature-insensitive operation. The device can achieve a thermal dependence around 13pm/°C in a wavelength range of 40nm. Owing to the utilization of one single straight multimode waveguide, the device is naturally immune to local temperature distributions.

Stepwise Fabrication of Co-Embedded Porous Multichannel Carbon Nanofibers for High-Efficiency Oxygen Reduction.

A novel nonprecious metal material consisting of Co-embedded porous interconnected multichannel carbon nanofibers (Co/IMCCNFs) was rationally designed for oxygen reduction reaction (ORR) electrocatalysis. In the synthesis, ZnCoO was employed to form interconnected mesoporous channels and provide highly active CoO/Co core-shell nanoparticle-based sites for the ORR. The IMC structure with a large synergistic effect of the N and Co active sites provided fast ORR electrocatalysis kinetics.

Controllable Construction of Core-Shell Polymer@Zeolitic Imidazolate Frameworks Fiber Derived Heteroatom-Doped Carbon Nanofiber Network for Efficient Oxygen Electrocatalysis.

Designing rational nanostructures of metal-organic frameworks based carbon materials to promote the bifunctional catalytic activity of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is highly desired but still remains a great challenge. Herein, an in situ growth method to achieve 1D structure-controllable zeolitic imidazolate frameworks (ZIFs)/polyacrylonitrile (PAN) core/shell fiber (PAN@ZIFs) is developed. Subsequent pyrolysis of this precursor can obtain a heteroatom-doped carbon nanofiber network as an efficient bifunctional oxygen electrocatalyst.

MOF-Based Metal-Doping-Induced Synthesis of Hierarchical Porous CuN/C Oxygen Reduction Electrocatalysts for Zn-Air Batteries.

A transition-metal-nitrogen/carbon (TM-N/C, TM = Fe, Co, Ni, etc.) system is a popular, nonprecious-metal oxygen reduction reaction (ORR) electrocatalyst for fuel cell and metal-air battery applications. However, there remains a lack of comprehensive understanding about the ORR electrocatalytic mechanism on these catalysts, especially the roles of different forms of metal species on electrocatalytic performance.

Interconnected Hierarchically Porous Fe, N-Codoped Carbon Nanofibers as Efficient Oxygen Reduction Catalysts for Zn-Air Batteries.

Developing porous carbon-based non-precious-metal catalysts for an oxygen reduction reaction (ORR) is a suitable approach to significantly reduce the costs of fuel cells or metal-air batteries. Herein, interconnected hierarchically porous carbon nanofibers simultaneously doped with nitrogen and iron (HP-Fe-N/CNFs) were fabricated by facile pyrolysis of polypyrrole-coated electrospun polystyrene/FeCl fibers. The obtained carbon nanofibers have a high specific surface area (569.