Seminar by Prof. Dr. Dennis M. Kochmann and Dr. Nguyen Truong Khang

On July 06, 2023, the lecture from Prof. Dr. Dennis M. Kochmann and Dr. Nguyen Truong Khang take place in meeting room A403.

Prof. Dr. Dennis M. Kochmann presents a talk entitled "Phase field modeling of the domain microstructure evolution in ferroelectric ceramics"

Abstract:

Ferroelectric ceramics show intricate domain microstructures, which, upon applying sufficient electric or mechanical bias fields, evolve over time and are responsible for the electro-mechanically coupled material behavior observable at larger scales. Understanding the kinetic evolution of domains during polarization switching is challenging, as it involves mechanisms that extend from the atomic scale of ferroelectric dipoles to the mesoscale of domain patterns to the macroscopic device level. In this seminar, we discuss phase-field modeling strategies to simulate such processes with the overall objectives of (i) predicting realistic microstructures and (ii) capturing the intricate kinetic, time-dependent evolution mechanisms. We will show that temperature-dependent phase-field models are appropriate for (i), while new approaches are required for (ii). Besides discussing the phase-field framework and its predictions, we also present experimental data that characterize the rate dependence of polarization reversal and the underlying domain-scale mechanisms.

Dr. Nguyen Truong Khang presents a talk entitled "Antenna Science and Technology: from microwave to Terahertz to optical frequency"

Abstract

Antenna is the key element in every wireless communication system. The science and technology of the antenna field ranges from microwave to terahertz to optical regimes. The congestion of the electromagnetic spectrum at microwave frequencies and the rapidly increasing demand for more bandwidth have attracted researchers for using higher-and-higher frequency waves as a solution to the increasing demand for fast data transmission over the past decade. While the operation mechanism of the microwave antenna is completely based on transport type with means of electronics devices; that of the optical antenna is based on transition type with means of photonic devices; however, that of the terahertz antenna mixes both that called photo-conductive mechanism. Thus, the high-frequency antenna has faced fundamental limits for compact and efficient sources. An efficient terahertz (THz) photoconductive antenna (PCA), as a major constituent for the generation or detection of THz waves, plays an essential role in bridging microwave-to-photonic gaps.