Perovskites for ultrafast active terahertz photonics

Abstract

In the electromagnetic spectrum terahertz (THz) frequency that lies between conventional electronics and photonics is vital due to its uniqueness and high potential for many disruptive applications such as security, high-resolution imaging, ultrasensitive sensors, and high-speed wireless communication for the sixth generation (6G). THz waves hold the potential to boost the key performance of many existing technologies thus, the emergence of THz photonics is inevitable. Hence, it is of paramount importance to develop the technology that provides unprecedented control on terahertz waves. The difficulties to control the properties of THz waves using natural existing materials led to the development of artificial composite materials known as metamaterial (MM). Metamaterial (MM) offers a simple and effective platform to develop the terahertz technologies owing to its scalable and on demand optical property that could be tuned. Active control of metamaterial response enables realization of THz functional devices. More importantly, the ability to control THz waves at ultrafast time scale is extremely crucial for developing next generation high-speed wireless communication. Integrating dynamic materials such as semiconductors with MM offers a possible solution. However, for commercial large-scale deployment a cost-effective high performing functional solution is desired for advance manipulation of THz waves in emerging THz technologies. This thesis aims to address these questions and provides a possible route to develop cost effective, easily integrable and high performing ultrafast THz photonic devices by integrating solution processed perovskite with metallic THz8 metamaterial (MM) structures. In the development of ultrafast active THz devices, the natural progression is to introduce multi functionalities in active metamaterial for advance manipulation of THz waves. In this context, the strong interaction of perovskite thin film with confined THz electric field offers a viable route to tune the carrier dynamics which is key to the foundation for next generation multifunctional active metamaterials. In this thesis, solution-processed perovskite has been explored to develop ultrafast THz photonics device. Fano resonant metamaterial structures owing to strong THz electric field confinement were employed to integrate with perovskites. The high photoconductivity and ultrafast free carrier dynamics in perovskite thin film enabled near unity modulation of THz electric field at ultrafast timescale. The existence of self-assembled quantum well (QW) in 2D perovskite provides an additional channel for the photoexcited free carrier to relax at ultrafast time scales (~ 20 ps) which is fastest in the family of solution processed semiconductors. We demonstrated 2D perovskite integrated hybrid metadevice at rigid as well as flexible platform that showed modulation of THz waves at ~ 50 GHz modulation speed. In the future prospect of the thesis we provide an outlook to achieve wavelength dependent response of active THz metadevice through integration of perovskites with silicon. The large bandgap tunability, ease of integration and ultrafast carrier dynamics of perovskite opens a new paradigm to develop multifunctional ultrafast active THz photonic devices for advance manipulation of THz waves.