Investigating wave-matter interactions in high-performance terahertz absorbers and the polariton states
Creators: name: Upadhyay, Aditi
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400699
subject: Communications engineering not elsewhere classified
classificationCode: 401605
subject: Functional materials

description: The way we view the world is dependent on the interaction of light and matter. We were able to greatly expand the range of objects that we could study very early on by combining our knowledge about the interaction of light with matter and the discovery of optical instruments. As electromagnetic radiation outside the visible range was discovered, a myriad of technological applications emerged, which inspired the development of a unified concept of light. There have been several visible microwave electromagnetic devices developed for different purposes. There is a growing interest in the terahertz spectral region of the electromagnetic spectrum. Due to its potential for scalability across different sectors, this regime is attracting both industrial and research interest. However, there are some bottlenecks in the development of terahertz technology. The strip that connects the electronic and optical worlds is relatively unexplored and is called the ‘terahertz gap’ because of its inaccessibility. Terahertz technology does not offer many practical applications at present, in part due to the lack of compact components that can be used to both generate and manipulate terahertz beams, as well as to detect and direct them. The terahertz regime can be further explored by harnessing micro and nano-scale fabrication techniques to lend tunable properties to electromagnetic devices. Successful implementation of terahertz technology means realizing device components that manipulate terahertz waves with high efficiency. This means continuously testing low-loss material and establishing fabrication techniques that will facilitate the fabrication of low-cost and miniaturized devices. The thesis focuses on novel materials and fabrication techniques for high-efficiency terahertz absorbers. The electromagnetic properties and operational frequencies will first be tested by full-wave electromagnetic simulations. These devices will then be fabricated by standard microfabrication techniques and evaluated with state-of-the-art Terahertz Time- Domain Spectroscopy (THz-TDS).

Furthermore, this thesis also aims to realize a targeted material functionality, namely electron transfer, by using coherent effects (strong coupling) as a tuning element at optical frequencies. In the case of the interaction of light with matter, a multidisciplinary field of strong coupling is observed. Several configurations of strong coupling under different ambient conditions have been investigated so far. As a result of this phenomenon, strong coupling in the fields of photonics, quantum communications, and biophysics holds a great deal of potential for future practical applications. Given the level of current interest, the wide range of specialist fields involved, and the rapidly developing capabilities afforded by a range of nanotechnologies, we can expect to see many new and unexpected developments emerge in the years ahead.