Large-Angle, Multifunctional Metagratings Based on Freeform Multimode Geometries

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.

Compounding Meta‐Atoms into Metamolecules with Hybrid Artificial Intelligence Techniques

“…However, photonic media with identical meta-atoms may offer only inadequate optimizing and designing nanophotonic devices. [15][16][17][18][19][20] To identify the optimized parameters of a device, the algorithm computes the gradient, or sensitivity, through the corresponding adjoint problem and updates the parameters along the deepestgradient direction. In addition to adjoint methods, genetic algorithms and related variations also play important roles in the design of photonic structures.…”

High-performance axicon lenses based on high-contrast, multilayer gratings

“…Ultra-thin metasurfaces consisting of subwavelength-scale structures have also been proposed to push the performance limits of blazed gratings operating at visible and infrared wavelengths. Initial metasurface-based deflectors took the form of titanium dioxide waveguide ensembles, 18 and more recent advances in this field have incorporated a range of geometrically simple [19][20][21][22][23] and topologically complex [24][25][26][27][28] nanowaveguide and nanoresonator architectures [ Fig. 1(d)].…”

MEMS-tunable dielectric metasurface lens

“…We attribute the slightly lower measured efficiency to fabrication imperfections. It is foreseeable that the efficiency can be significantly improved with better optimization and design processes 35 , use of antireflection coatings to reduce reflection losses, and optimizing the fabrication process.…”

“…In the optical regime, dielectric metasurfaces are very versatile as they allow for wavefront control with high efficiency and subwavelength resolution. Several devices with the ability to control the phase [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] , polarization 38,39 , polarization and phase 40 , or spectral components of light through harmonic generation [41][42][43] or filtering [44][45][46][47] have been demonstrated. Their thin form factor makes them suitable for development of ultrathin conformal optical elements 48,49 , and their compatibility with conventional micorfabrication techniques allows for monolithic fabrication of optical systems consisting of multiple metasurfaces on a single chip 50,51 .…”