Efficient Cross-talk Reduction of Nanophotonic Circuits Enabled by Fabrication Friendly Periodic Silicon Strip Arrays

Yusheng Bian,Lei Kang,Pingjuan L. Werner,Yifeng Qin,Douglas H. Werner,Qiang Ren

doi:10.1038/s41598-017-16096-9

Yusheng Bian, Lei Kang + Show 4 more

Open Access

https://doi.org/10.1038/s41598-017-16096-9

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Abstract

Reduction of the crosstalk between adjacent photonic components has been regarded as one of the most effective, yet most challenging approaches for increasing the packing density of photonic integrated circuits. Recently, extensive efforts have been devoted to this field, leading to a number of elaborate designs, such as waveguide supperlattice and nanophotonic cloaking, among others. Here we develop a simple and efficient crosstalk reduction approach for silicon-based nanophotonic circuits by introducing a periodic array of silicon strips between adjacent waveguides. Studies indicate that the coupling lengths can be extended by more than two orders of magnitude for a waveguide pair with an edge-to-edge distance of ~λ/3 at the telecommunication wavelength. Further investigations reveal that our method is effective for both strongly and weakly confined silicon photonic modes, and works well over a broad band of operational wavelengths. In addition, the crosstalk reduction technique is shown to be capable of improving the coupling lengths of other elements as well, such as vertical silicon slot waveguides. Our approach offers a promising platform for creating ultra-compact functional components that is fabrication friendly, thereby providing a feasible route toward the realization of photonic integrated circuits with ultra-high packing densities.

Highlights

Nanophotonic cloaking[17] represent highly efficient approaches capable of enabling half-wavelength-scale waveguide spacing with negligible crosstalk at telecommunication wavelengths, which is a significant improvement relative to the state-of-the-art technology
To further simplify the design process, here we develop an alternative and much simpler approach to reduce the crosstalk in nanophotonic circuits by introducing a periodic array of silicon strips between adjacent waveguides
As revealed in recent work[18,19], the penetration depth of the evanescent fields into the surrounding medium is governed by the ratio of the permittivity components along different directions. This finding enables us to flexibly control the spatial field distribution of waveguides through tuning the permittivity ratios, leading to unprecedented confinement capabilities that are otherwise difficult to achieve using all-dielectric configurations[18]. We apply such a concept to reduce the overlap between the evanescent waves of the guided modes and minimize the crosstalk between neighboring silicon-based nanophotonic waveguides

Summary

Introduction

Nanophotonic cloaking[17] represent highly efficient approaches capable of enabling half-wavelength-scale waveguide spacing with negligible crosstalk at telecommunication wavelengths, which is a significant improvement relative to the state-of-the-art technology. In these studies, elaborate design schemes based on the interlacing-recombination supercell principle or inverse-design techniques for discrete binary pixels were exploited in order to obtain optimized configurations. Our design is straightforward, such that it neither requires a complex algorithm for structure optimization nor a sophisticated process in device fabrication This approach can be applied to various types of photonic devices as well and enables efficient crosstalk reduction across a broad band of operation wavelengths

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