Scalable Metasurface Building Blocks for Arbitrary On-chip High-order Mode Manipulation

Abstract

On-chip integrated mode-division multiplexing (MDM) has been emerging as a promising technology to further improve the link capacity and satisfy the continuously increasing bandwidth demand in data communications. One of the most important components in MDM and multimode photonics is a mode converter. While several configurations have been developed to realize on-chip mode converters, it is still very challenging to achieve versatile high-order mode converters with high performance in a generic way to reduce the R&D and prototyping costs. Here we initiate a breakthrough utilizing a simple yet universal generic building block concept with metasurface structures to implement programmable arbitrary highorder mode converters with competitive performance, high reliability and compact footprints. The building block, i.e., the TE0-TE2 mode converter is first introduced to illustrate the generic concept, which exhibits low insertion loss of 0.3 dB, low crosstalk of -10 dB across broad wavelength band of 250 nm with a footprint of 2.7×1.3 µ 2 m . All even-order and odd-order mode converters can be realized by directly programming multiple parallel basic building blocks and coarsely engineering the waveguide widths simply in a universal approach. The proposed mode converter building blocks for high-order mode conversion highlight features of uniform performance with broad bandwidth, low insertion loss, compact footprints and good fabrication tolerance, plus the uniquely simple and scalable generic fashion, making them extremely attractive for on-chip multimode optical interconnections.

Metamaterial-enabled arbitrary on-chip spatial mode manipulation

“…Previously, we have demonstrated that a single dielectric slot can function as a power splitter and a phase shifter simultaneously 33 , which inspires the implementation of beam shaping principle completely with metamaterial BBs consisting of fully etched dielectric slots (more information about the origin of metamaterial BBs is provided in Supplementary Note 1 ). Considering the symmetry property of electric field profiles of eigenmodes, the TE 0 -TE 2 metamaterial BB 38 is designed with a symmetric arrow-like shape, as depicted in Fig. 1c .…”