Stability and optical tunability of flexible BST membrane observed in terahertz band

Ferroelectric materials are generally inflexible in their normal state, and our synthesized barium strontium titanate (BaxSr1-xTiO3, X = 0.6, BST) films are so elastic and flexible that they can be bent at about 140. The flexibility of the BST film prevents the material from fracturing due to mismatching forces. We demonstrate by THz-TDS (Terahertz time domain spectroscopy) system that the fabricated flexible BST film maintains a stable transmittance under different bending conditions. In addition, under an external optical pump, the transmittance amplitude can be modulated by about 90%. This property can be used in the design of tunable terahertz devices in the case of additional pumps. The film's flexibility and the possibility of further tuning will expand the range of applications for wearable terahertz devices to be developed in the near future.