Electrically Tunable Transparent Displays for Visible Light Based on Dielectric Metasurfaces

Abstract

Tunable dielectric metasurfaces able to manipulate visible light with high efficiency are promising for applications in displays, reconfigurable optical components, beam steering, and spatial light modulation. Infiltration of dielectric metasurfaces with nematic liquid crystals (LCs) is an attractive tuning approach, which is highly compatible with existing industrial platforms for optical and electronic devices. Here, we demonstrate electrically tunable transparent displays based on nematic LC-infiltrated tunable dielectric metasurfaces at visible frequencies. Importantly, the technique of photoalignment of LCs is adopted to improve the LC prealignment quality and thus the tuning accuracy and contrast in the visible. By applying a voltage across the infiltrated metasurface cell, we observe resonance shifts that are more than twice larger than their line width. We track the spectral shifts of the electric and magnetic dipole resonances as they move into and out of the so-called Huygens' regime of high transparency originating from spectrally overlapping electric and magnetic dipole resonances. Furthermore, we realize a switchable metasurface display with a measured modulation depth of 53% at 669 nm operation wavelength for an applied voltage of 20 V. The novel LC tuning platform demonstrated in our work may lead to the development of next-generation LC display devices that are able to overcome current limitations of minimal pixel size and speed of operation.

Design for quality: reconfigurable flat optics based on active metasurfaces

“…In liquid crystals, the birefringent molecules can be reoriented along the electric field direction, thereby creating a large refractive-index change possibly exceeding 0.3 [100]. By immersing metasurface structures in a liquid crystal cell, electrical tuning of resonances in plasmonic [101][102][103][104] and dielectric [105,106] resonator arrays has been demonstrated. Electrically tunable liquid crystal metasurfaces engineered using an inverse-design approach have demonstrated high-efficiency and wide-angle steering performances [107].…”

Progresses in the practical metasurface for holography and lens

“…When a meta-atom is designed using a material whose permittivity changes by external bias, the metasurface can contain more than one information without change of incident light properties. In the optical frequency domain, well-known phase change materials such as vanadium oxide, liquid crystal, indium tin dioxide (ITO), and GeSbTe (GST) based materials have been actively employed as dynamic nanophotonic devices so far [60,80,[84][85][86][87][88]. Especially, GST is a material whose state changes from amorphous into crystalline and vice versa according to external stimuli such as thermal or electrical bias [89,90].…”

Phase Change Metasurfaces by Continuous or Quasi-Continuous Atoms for Active Optoelectronic Integration

“…In principle, all those actively reconfigurable metasurfaces can be constructed by: (i) embedding active materials or components into hybrid device architectures, or (ii) directly structuring into thin films of active materials (e.g., graphene [ 32 , 33 , 34 ], phase change chalcogenides [ 35 , 36 , 37 ]). After a close inspection and classification, such active materials or mechanisms include the liquid crystal (LC) [ 38 ], MEMS [ 39 , 40 ], semiconductors [ 41 , 42 ], the 2D materials family represented by graphene [ 43 , 44 , 45 ], atomic-thin-layer direct tuning of 2D electron gas [ 46 ], conductive metal oxide (i.e., Indium Tin Oxide ITO) [ 10 , 47 , 48 , 49 ], magnetic or ferromagnetic materials [ 50 , 51 ], varactor arrays [ 52 , 53 , 54 ], and phase change materials (PCMs) [ 28 , 29 , 30 , 36 , 55 , 56 , 57 , 58 ]. Among these mainstream options, the LC-based methods are commonly used for conventional optical modulation, but with intrinsic obstacles in CMOS-compatibility and high-speed operations, especially for integrated photonics.…”