Nanoimprinting Solution-Derived Barium Titanate for Electro-Optic Metasurfaces

Abstract

Electro-optic metasurfaces have demonstrated significant potential in enhancing the modulation speed and efficiency for fast and large-scale freespace optical devices. Barium titanate has a strong electro-optic Pockels coefficient, but its availability in thin-film form is restricted due to costly growth processes or low thickness. Here, we fabricated active metasurfaces using an etch-free bottom-up process with sol−gel-based polycrystalline barium titanate with a large electro-optic coefficient similar to bulk lithium niobate. We achieve strong hybrid Mie/surface lattice resonances with a quality-factor of 200 at 633 nm wavelength, enhancing the light−matter interaction and therefore the Pockels effect. The metasurface transmission is electro-optically modulated with up to 5 MHz driving frequency at low voltages of less than 1 V thanks to resonant enhancement of the modulation amplitude by 2 orders of magnitude. This successful demonstration of electro-optic modulation in nanoimprinted barium titanate structures paves the way for low-cost and large-scale free-space modulators or tunable metalenses.

Advanced manufacturing of dielectric meta-devices

“…spectrum from UV to IR wavelengths, hold promise for enhancing metasurface performance. Furthermore, the emergence of multifunctional dielectric materials with tunable optical properties, including phase-change materials such as germanium antimony telluride (Ge 2 Sb 2 Te 5 or GST) [339] , vanadium dioxide (VO 2 ) [340] , and antimony trisulfide (Sb 2 S 3 ) [341] ; electro-optic materials like lithium niobate (LiNbO 3 ) [342] ; and thermo-optic materials like silicon (Si) [343] and liquid crystals [344] ; as well as electrical properties, such as ferroelectric materials like barium titanate (BaTiO 3 ) [345] and graphene [346] ; magnetic properties, such as multiferroic materials like bismuth ferrite (BiFeO 3 ) [347] ; and magneto-optic materials like yttrium iron garnet (YIG) [348] , along with intensity-modulated nonlinear materials like metallic quantum wells [349][350][351] , offers versatile options for metasurface fabrication and functionality enhancement. The combination of tunable properties in these materials has shown promising applications in dynamic, reconfigurable, and high-performance dielectric metasurfaces, including dynamic holograms [352] , tunable imaging [353][354][355] , active beam steering [356] , and chirality tuning in several recent studies [341] .…”