Tuning the dielectric properties of LiNbO3 based interdigitated electrode metastructure in the terahertz range

Abstract As a tunable optical material, LiNbO3 crystal has attracted broad interest in the last several decades. Despite wide applications in optical band as electrooptic modulators or piezoelectric sensors, the tunability of LiNbO3 in terahertz band is very limited, which restrains its performance as practical devices. Here we experimentally and theoretically demonstrate the dielectric permittivity spectrum of an integrated LiNbO3 interdigitated electrode meta-structure by terahertz time-domain spectroscopy ranging from 0.4-1.5 THz at room temperature. Under external electrical and optical fields pump, a considerable tuning of absorption coefficient of the sample can be achieved, which rendered a modulation of transmission amplitude reaching up to 13.3%. The observations are attributed to the strong absorption of ionized carriers induced by electrical and optical excitation. Our design appreciably modulates the dielectric property of unpatterned LiNbO3 crystals by the application of a metal interdigital electrode on the surface, and provides a reference for potential applications on tunable photonic devices in terahertz range.