Physics Seminar
Resonant states: From chiral sensing to Mie voids
Speaker: Thomas Weiss (University of Graz)
Date: Wednesday 22 February 2023
Time: 15:00
Venue: Queens Building N3.28
Resonant phenomena are the dominating effects in nanophotonic systems, i.e., structures on the order of the optical wavelength in use. They can be attributed to resonant states and their interplay. Resonant states are solutions of Maxwell's equations in the absence of external and internal sources and comprise an overcomplete set of basis states. We are going to briefly introduce the theory of these resonant states [1] and then apply it to two important examples. The first one is chiral sensing. Chirality is the geometrical property that an object is not identical to its own mirror image. The object and its mirror image are then said to have opposite handedness. A lot of objects in nature are chiral, including DNA. Since the interaction of chiral objects depends on their mutual handedness, there exist molecules, of which one handedness can be used as a medical drug, while the other handedness can be harmful. Hence, handedness discrimination is of utmost importance. One way is using chiral light to determine the handedness. However, the chiral light-matter interaction is rather weak. Resonant enhancement via nanophotonics is one promising route for better handedness discrimination. We present a rigorous theory for this enhancement and provide possible strategies for optimized systems [2]. Finally, we will introduce the rather new concept of confining light in small cavities inside a high-index dielectric, so-called Mie voids [3]. We will provide some basic theory and discuss their potential in nanophotonics. It turns out that resonant states in Mie voids are rather insensitive to the surrounding material, which allows to obtain resonant states down to the ultraviolet. Also, the voids can be filled with different materials, making them good candidates for sensing applications. [1] S. Both and T. Weiss, Resonant states and their role in nanophotonics, Semicond. Sci. Technol. 37, 013002 (2022). [2] S. Both, M. Schäferling, F. Sterl, E. A. Muljarov, H. Giessen, and T. Weiss, Nanophotonic chiral sensing: ow does it actually work ACS Nano 16, 2822-2832 (2022). [3] M. Hentschel, K. Koshelev, F. Sterl, S. Both, J. Karst, L. Shamsafar, T. Weiss, Y. Kivshar, and H. Giessen, Dielectric Mie voids Confining light in air, Light Science Applications 12, 3 (2023).