Bidirectional luminescence modulation of BTO:Yb/Er ferroelectric films based on phase transition

Abstract

Lanthanide-activated ferroelectric films exhibit dynamic and reversible luminescence modulation under external electric fields, making them promising candidates for applications in optical communication and information storage. To date, all reported studies have observed only unidirectional luminescence under both positive and negative biases. This is because polarization-induced reduction of lattice symmetry occurs under both positive and negative biases. Herein, a new phenomenon of luminescence, enhanced at positive voltages and weakened at negative voltages, was observed for the first time. Under a positive bias, parts of the rhombohedral phase were transformed into a tetragonal phase. On the contrary, parts of the tetragonal phase transformed into a rhombohedral phase under a negative bias. The phase transition between the tetragonal and rhombohedral phases of Yb³⁺/Er³⁺ co-doped BaTiO₃ (BTO:Yb/Er) was demonstrated as the reason for this specific bidirectional regulation. The critical coexistence of tetragonal and rhombohedral phases in the BTO:Yb/Er thin film was obtained on the substrate upon inducing tensile strain in the BTO:Yb/Er thin film. Encoding experiments demonstrated that this bidirectional luminescence modulation in the BTO:Yb/Er film improved the transmission speed and bandwidth of the optical signals in light modulation, offering a novel strategy for optical modulation in information encoding and related fields.