Electro-mechanical to optical conversion by plasmonic-ferroelectric nanostructures

Barium titanate (BaTiO3) is a lead-free ferroelectric crystal used in electro-mechanical transducers and electro-optic films. Nanomechanical devices based on thin films of BaTiO3 are still unavailable, as the internal stress of thin ferroelectric films results in brittle fracture. Here, we use the electro-mechanical force to fabricate deformable assemblies (nanobeams) of BaTiO3 nanocrystals, on top of plasmonic metasurfaces. The mechanical deformation of the nanobeams is driven by the piezoelectric response of the BaTiO3 nanocrystals. The plasmonic-ferroelectric nanostructures due to the plasmonic enhancement enable subwavelength interaction lengths and support reflection modulation up to 2.936 ± 0.008%. Their frequency response is tested across 50 kHz up to 2 MHz and is dependent on the mechanical oscillations of the deformable BaTiO3 nanobeams. The ferroelectric nanobeams support mechanical nonlinearities, which offer additional control over the electro-mechanical to optical conversion.