Large-Angle, Multifunctional Metagratings Based on Freeform Multimode Geometries

TLDR

These silicon‑based metagratings use nonintuitive nanoscale patterns that support many overlapping optical modes, providing the degrees of freedom needed for high‑efficiency devices and representing a new paradigm in nano‑optical mode engineering distinct from current waveguide‑stitching approaches. The authors aim to demonstrate the versatility of inverse design by fabricating metagratings that deflect light to 75° and steer beams to different diffraction orders, envisioning new high‑performance photonic systems and nanoscale light‑field control. The study uses inverse freeform design and theoretical Bloch‑mode analysis to fabricate metagratings that deflect light to 75° and steer beams to different diffraction orders, revealing the mode profiles and coupling dynamics enabling high‑performance beam deflection. The authors demonstrate that silicon‑based metagratings designed via inverse freeform methods achieve large‑angle, multifunctional performance.

Abstract

We show that silicon-based metagratings capable of large-angle, multifunctional performance can be realized using inverse freeform design. These devices consist of nonintuitive nanoscale patterns and support a large number of spatially overlapping optical modes per unit area. The quantity of modes, in combination with their optimized responses, provides the degrees of freedom required to produce high-efficiency devices. To demonstrate the power and versatility of our approach, we fabricate metagratings that can efficiently deflect light to 75° angles and multifunctional devices that can steer beams to different diffraction orders based on wavelength. A theoretical analysis of the Bloch modes supported by these devices elucidates the spatial mode profiles and coupling dynamics that make high-performance beam deflection possible. This approach represents a new paradigm in nano-optical mode engineering and utilizes different physics from the current state-of-the-art, which is based on the stitching of noninteracting waveguide structures. We envision that inverse design will enable new classes of high-performance photonic systems and new strategies toward the nanoscale control of light fields.