Electrically focus-tuneable ultrathin lens for high-resolution square subpixels

Abstract

Owing to the tremendous demands for high-resolution pixel-scale thin lenses in displays, we developed a graphenebased ultrathin square subpixel lens (USSL) capable of electrically tuneable focusing (ETF) with a performance competitive with that of a typical mechanical refractive lens. The fringe field due to a voltage bias in the graphene proves that our ETF-USSL can focus light onto a single point regardless of the wavelength of the visible light-by controlling the carriers at the Dirac point using radially patterned graphene layers, the focal length of the planar structure can be adjusted without changing the curvature or position of the lens. A high focusing efficiency of over 60% at a visible wavelength of 405 nm was achieved with a lens thickness of <13 nm, and a change of 19.42% in the focal length with a 9% increase in transmission was exhibited under a driving voltage. This design is first presented as an ETF-USSL that can be controlled in pixel units of flat panel displays for visible light. It can be easily applied as an add-on to high resolution, slim displays and provides a new direction for the application of multifunctional autostereoscopic displays.

Scalable and High-Throughput Top-Down Manufacturing of Optical Metasurfaces

“…Contact and proximity printing can produce patterns down to a few micrometers [62], therefore cannot fulfill the sub-micrometer resolution required for optical metasurfaces that operate at visible frequencies. A number of techniques have been employed to achieve an increased resolution by manipulating the parameters in Equation (1). Projection printing has drawn great attention due to the ability to create high-resolution and large-scale arrays despite having a relatively small photomask, by using additional projection optics [62,63].…”

“…Metasurfaces, on the other hand, have been considered as a promising candidate for the replacement of conventional lenses. They have been applied as high-resolution ultrathin lenses [ 1 , 2 ], as well as superlenses and hyperlenses that overcome diffraction limits [ 3 , 4 , 5 ]. Metasurfaces can also play the role of color filters, selectively transmitting or reflecting the specific wavelengths of incident light to produce the desired colors [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ].…”

Focus‐Tunable Planar Lenses by Controlled Carriers over Exciton

“…Generally, there are two possible ways of inducing external electric field on the graphene, as shown in Figure S1 (Supporting Information): vertical and horizontal. However, the horizontal electric field [ 27 ] requires two adjacent graphene rings as the two electrodes, which limits the field formation at the center of the rings. Meanwhile, vertical electric field is capable of concentrating more carriers over a wider range of areas on the rings, since the common bottom electrode with a much wider surface area serves as an adjacent electrode.…”

A micromirror array with annular partitioning for high-speed random-access axial focusing

“…Namely, acousto-optic and electro-optic modulation approaches, which offer refresh rates of up to 1 MHz 14 , have become increasingly popular in recent years with the widespread adoption of tools such as acousto-optic deflectors for lateral scanning 45 . Unfortunately, this benefit of ultrafast responsivity has not translated into viable high-speed axial focusing, as limitations in the control and sensitivity result in performance costs such as drastic insertion loss 46 or high voltage drive requirements 47 . In addition, MEMS structures have the distinct advantage of being ideal dynamic substrates for metamaterials.…”