Tunable Infrared Devices via Ferroelectric Domain Reconfiguration

Abstract Despite widespread use in sensing, electro‐optics, and catalysis, plasmonic elements are typically static in their spectral response. The subwavelength spatial confinement and enhanced electric fields intrinsic to plasmons provide a lever to realize dynamic spectral tunability—and thus multifunctional optical components—as small alterations in their dielectric environment are amplified by these effects. Here, electric‐field (DC) control of phonon modes is leveraged in lead zirconate titante (PZT) ferroelectric bilayers to create tunable long‐wave infrared (LWIR) plasmonic devices that demonstrate a combination of advantages—speed (>10 kHz), latching, and low‐power switching (<1 µJ mm⁻²)—unavailable together in approaches reported heretofore. Mechanistically, bias‐induced domain reconfiguration alters the phonon energies defining PZT's optical permittivity, which determines the gap plasmon formed within the ferroelectric resting between patterned metal contacts. The utility of ferroelectrics for tunable plasmonic devices is thus demonstrated while highlighting the promise of leveraging phonons for these purposes.