GaN Metalens for Pixel-Level Full-Color Routing at Visible Light

Abstract

Metasurface-based components are known to be one of the promising candidates for developing flat optical systems. However, their low working efficiency highly limits the use of such flat components for feasible applications. Although the introduction of the metallic mirror has been demonstrated to successfully enhance the efficiency, it is still somehow limited for imaging and sensing applications because they are only available for devices operating in a reflection fashion. Here, we demonstrate three individual GaN-based metalenses working in a transmission window with extremely high operation efficiency at visible light (87%, 91.6%, and 50.6% for blue, green, and red light, respectively). For the proof of concept, a multiplex color router with dielectric metalens, which is capable of guiding individual primary colors into different spatial positions, is experimentally verified based on the design of out-of-plane focusing metalens. Our approach with low-cost, semiconductor fabrication compatibility and high working efficiency characteristics offers a way for establishing a complete set of flat optical components for a wide range of applications such as compact imaging sensors, optical spectroscopy, and high-resolution lithography, just named a few.

A review of dielectric optical metasurfaces for wavefront control

“…As a result, more groups started investigating the High-Contrast transmit/reflect Array (HCTA/HCRA or HCA) structures (similar to the one shown in Fig. 1f) that use thicker (about 0.5λ to λ) high-index layers to pattern the metasurface [13,38,[65][66][67][68][69][70][71][72][73][74]. These structures are very similar to the blazed binary optical elements that are at least two decades old [75][76][77][78], nevertheless, they outperform other classes of metasurfaces in many wavefront manipulation applications.…”

“…Most of the demonstrated methods result in multi-wavelength devices and are in principle similar to the multi-order diffractive optical elements [31, 73, 74, 165-169, 173, 175, 176, 179]. More recently, a method based on independent control of phase and its wavelength derivative (dispersion) has been introduced [180] and used to implement achromatic [73,119,170,180,181] and dispersionengineered [119] FIG. 4 Multi-wavelength and dispersion-engineered metasurfaces.…”

“…(a) An example of a spatially-multiplexed multi-wavelength metasurface through interleaving of GaN meta-atoms. Four lenses are multiplexed to separate RGB colors [73]. (b) Concept of a multi-wavelength metasurface lens multiplexed through segmentation [165].…”

“…The simplest method used to demonstrate mutiwavelength devices is based on spatial multiplexing of metasurfaces [73,74,165,176,177,182,183]. In this method, multiple metasurfaces are designed for multiple wavelengths (one for each wavelength).…”

A Multi‐Foci Metalens with Polarization‐Rotated Focal Points

“…In comparison with traditional bulk lenses that rely on the required gradual phase change accomplished by controlling surface profile of the optical material, metalenses are ultrathin and ultraflat, which is desirable for device miniaturization and system integration. As fundamental optical elements, metalenses have shown promising applications in imaging, lithography, spectroscopy, and laser fabrication due to the ultrathin configuration and ease of fabrication. In addition, metalenses can provide novel functions that are very challenging or impossible to achieve with conventional lenses, which can extend the imaging capability of the current optical systems.…”