Title: Engineering the optical properties of molecular materials: what, why, and how?

Speaker: Dr. Adarsh Vasista, ETH, Zurich, Switzerland

Abstract: The way molecules absorb, transfer, and emit light can be modified by coupling them to optical cavities. The extent of the modification is often defined by the cavity–molecule coupling strength. We can define two coupling regimes depending on the value of the coupling strength: (a) Weak coupling regime and (b) strong coupling regime. In the weak coupling regime, the molecule cavity coupling strength is less than the losses in the system while in the strong coupling regime the coupling strength exceedsthe losses and results in the formation of new hybrid energy states.

Both metallic and dielectric cavities have been proposed and used to achieve molecule cavity coupling. Due to the presence of collective charge oscillations at the surface (also called surface plasmon resonance), metallic cavities provide very large electric field strength. However, they suffer from the joule heating losses. On the other hand, dielectric cavities do not suffer from heating losses and support spectrally sharp resonances, but they do not provide large field strengths. We utilize both metallic and dielectric cavities depending on the target application.

In the first half of the talk, I will focus on our efforts on how to utilize both metallic and dielectric cavities to engineer wavevector [1] and polarization [2] of molecular emission in the weak coupling regime. Subsequently, I will shift gears and expand on our efforts in understanding strong molecule-cavity coupling using dielectric cavities[3,4].

References:

[1] A B Vasista et.al., Nano Lett., 18, 1, 650–655 (2018)

[2] A B Vasista et al., Adv. Opt. Mater., 6, 1801025 (2018)

[3] A B Vasista et.al., Nano Lett., 20, 1766–1773 (2020)

[4] A B Vasista et.al., Nano Lett., 22, 6737–6743 (2022)