Electrical Tuning of Fresnel Lens in Reflection

Abstract

Optical metasurfaces have been extensively investigated, demonstrating diverse and multiple functionalities with complete control over the transmitted and reflected fields. Most optical metasurfaces are, however, static, with only a few configurations offering (rather limited) electrical control, thereby jeopardizing their application prospects in emerging flat optics technologies. Here, we suggest an approach to realize electrically tunable optical metasurfaces, demonstrating dynamic Fresnel lens focusing. The active Fresnel lens (AFL) exploits the electro-optic Pockels effect in a 300 nm thick lithium niobate layer sandwiched between a continuous thick and a nanostructured gold film serving as electrodes. We fabricate and characterize the AFL, focusing 800−900 nm radiation at a distance of 40 μm, with the focusing efficiency of 15%, and demonstrating the modulation depth of 1.5%, with the driving voltage of ±10 V within the bandwidth of ∼6.4 MHz. We believe that the electro-optic metasurface concept introduced is useful for designing dynamic flat optics components.

Performance Analysis of DAST Material-Assisted Photonic-Crystal-Based Electrical Tunable Optical Filter

“…Additionally, the integrated material should possess a correspondingly large coefficient of variations. This enables developing a number of tunable surface wave-based nano-photonic devices [15][16][17]. Recently, tunable narrowband spectral filters have gained considerable attention because of their wide applications in spectroscopy, imaging, sensing, smart display and astronomy [18][19][20][21][22][23].…”

Gigahertz free-space electro-optic modulators based on Mie resonances

“…Ultrathin electro-optic modulators from sub-wavelength resonators are exquisite candidates in applications that require tailor-cut control over free-space light in a compact way, such as free-space optical communication links 21 , coherent laser ranging, active optical components 22 , high-speed spatial light modulators 23 , 24 and active control of free-space emitters 25 . Flat optical components such as metasurfaces 26 , 27 rely on sub-wavelength-sized nanostructures that change the properties of a beam that is incident from free space onto the metasurface, and are ideally suited to address spatial multiplexing needs beyond the single pixel.…”

Active multiband varifocal metalenses based on orbital angular momentum division multiplexing

“…But, the realization of the great important varifocal function is still confronted with vicious difficulties, such as the poor ability of active regulation 31 – 33 , narrow working band 34 , and small depth of field (DOF) 35 , 36 . At present, they can actively control the optical field by refractive index control 5 , 37 , 38 , material transformation 31 , electromagnetic resonance control 39 , 40 , and electrodeformation 41 . However, it is still unable to achieve the active varifocal, especially, in the visible band, because of the single mode of regulation and limited processing capacity.…”