Silicon-Based TM0-to-TM3 Mode-Order Converter Using On-Chip Shallowly Etched Slot Metasurface

Abstract

Mode-order converters drive the on-chip applications of multimode silicon photonics. Here, we propose a TM0-to-TM3 mode-order converter by leveraging a shallowly etched slot metasurface pattern atop the silicon waveguide, rather than as some previously reported TE-polarized ones. With a shallowly etched pattern on the silicon waveguide, the whole waveguide refractive index distribution and the corresponding field evolution will be changed. Through further analyses, we have found the required slot metasurface pattern for generating the TM3 mode with high conversion efficiency of 92.9% and low modal crosstalk <−19 dB in a length of 17.73 μm. Moreover, the device’s working bandwidth and the fabrication tolerance of the key structural parameters are analyzed in detail. With these features, such devices would be beneficial for the on-chip multimode applications such as mode-division multiplexing transmission.

Optical mode conversion via modulated atomic samples

“…Thus, mode-converting devices have been designed to modify light in environments such as waveguides, cavities, and photonic crystals that limit the occupiable spatial modes to enhance conversion to a single target mode. Among these devices are a HG↔LG mode converter using an astigmatic microcavity [52], an arbitrary HG mode-order converter utilizing the impedance mismatches between coupled Fabry-Pérot resonators [53], design-by-specification converters based on computational methods [54], and an assortment of silicon photonic converters that harness refractive index variation to smoothly modify a propagating spatial mode [55][56][57][58][59][60][61][62][63][64][65][66][67].…”