Decoupling optical function and geometrical form using conformal flexible dielectric metasurfaces (1511.04824v2)

Abstract: Physical geometry and optical properties of objects are correlated: cylinders focus light to a line, spheres to a point, and arbitrarily shaped objects introduce optical aberrations. Multi-functional components with decoupled geometrical form and optical function are needed when specific optical functionalities must be provided while the shapes are dictated by other considerations like ergonomics, aerodynamics, or esthetics. Here we demonstrate an approach for decoupling optical properties of objects from their physical shape using thin and flexible dielectric metasurfaces which conform to objects' surface and change their optical properties. The conformal metasurfaces are composed of silicon nano-posts embedded in a polymer substrate that locally modify near-infrared ($\it{\lambda}$ = 915 nm) optical wavefronts. As proof of concept, we show that cylindrical lenses covered with metasurfaces can be transformed to function as aspherical lenses focusing light to a point. The conformal metasurface concept is highly versatile for developing arbitrarily shaped multi-functional optical devices.

• The paper presents the innovative decoupling of optical function from geometrical form using flexible dielectric metasurfaces to transform cylindrical lenses into aspherical ones.
• It employs silicon nano-posts on a PDMS substrate to achieve a complete 0–2π phase control with over 91% transmission efficiency at 915 nm.
• The approach has practical implications for miniaturized optics in consumer electronics, medical devices, and advanced photonic applications.

Conformal Flexible Dielectric Metasurfaces: Design and Application

The paper "Decoupling optical function and geometrical form using conformal flexible dielectric metasurfaces" presents an innovative approach in the domain of optical engineering, where the longstanding challenge of correlating an object's geometry with its optical properties is addressed. This work delineates the development and theoretical grounding for flexible dielectric metasurfaces that can conform to arbitrary surfaces while independently tailoring optical functionalities. The authors, Kamali et al., demonstrate their approach by manipulating simple cylindrical lenses to function as aspherical lenses, thereby illustrating the versatility and potential applications of their technology.

The research hinges on the concept of metasurfaces—planar optical elements composed of subwavelength scatterers that can impart desired phase shifts to incident electromagnetic waves. In this paper, the metasurface comprises silicon nano-posts on a flexible polydimethylsiloxane (PDMS) substrate. The metasurfaces are capable of manipulating near-infrared light at a specific wavelength (915 nm), with the aim of transforming cylindrical lenses so that they focus light to a point rather than along a line, effectively decoupling physical form from optical function.

The authors pursue a detailed numerical and experimental validation, underlining the capacity of the designed metasurfaces to provide a targeted phase compensation necessary to correct optical aberrations caused by non-planar substrate surfaces. The metasurfaces achieve over 91% transmission efficiency, covering the full $0$ to $2\pi$ phase range with nano-post structures, a significant enhancement over plasmonic counterparts limited by lower efficiencies in transmission mode.

One of the significant claims made in the paper is the successful application of their conformal metasurface platform across varied substrate shapes. They utilize high contrast transmitarrays based on amorphous silicon nano-posts—each acting almost independently due to weak optical coupling—to dictate the wavefront transmission characteristics locally. The fabrication process ensures these metasurfaces remain functional after transfer to non-standard surfaces, validated through a thorough set of microscopy and optical assessments.

The practical implications of this research span various domains, including the miniaturization of optical components in consumer electronics, medical devices, and potential deployment in optical cloaking and camouflage technologies. By introducing a versatile method for tailoring the optical path difference without altering the opaqueness of the physical shape, it opens avenues for complex, conformal optical devices that seamlessly integrate into existing designs dictated by non-optical requirements.

Future developments in this area could focus on extending the metasurface capabilities across wider spectral ranges and enhancing their functionality under broader environmental conditions, including larger angles of incidence and non-linear optical environments. This paper's methodology might also influence future research into integrating these metasurfaces with flexible electronics, further augmenting their utility in sophisticated photonic applications.

In conclusion, Kamali et al.'s paper represents a noteworthy advancement in the control of electromagnetic wavefronts through the independent manipulation of geometrical and optical properties—a technique of considerable interest and promise in the field of photonic engineering.