UC San Diego

The detection and manipulation of matter with light is a ubiquitous goal of chemistsand physicists. However, this endeavor faces inherent challenges due to the typically “weak” light-matter interaction and discrepancy in scale between molecules and the spatial variation of the electromagnetic field. Such limitations hinder the ability to differentiate between similar molecules and effectively modify their characteristics.

In this dissertation, we seek to transcend the limitations of typical light-matter interactionsby introducing innovative laser protocols and venturing into the realm of strong coupling. We aim to overcome the challenges attributed to natural and magnetically-induced optically activity and demystify phenomena intriguing to molecular polaritonic phenomena.

We begin by proposing a laser setup to generate synthetic gauge fields within molecularaggregates to induce a molecular excitonic version of the Aharovon-Bohm effect. Even though the undriven system is achiral, this laser-induced effect generates a non-zero circular dichroism signal. Notably, an unfeasibly strong static magnetic field is needed to generate a similar effect in electronic systems. Next, we introduce a modified microwave three-wave mixing setup to achieve enantioselective topological frequency conversion. This approach, representing the first instance of a chiroptical spectroscopic signal directly linked to a topological invariant, underscores the potential of using topological principles to enhance the sensitivity and robustness of spectroscopic techniques for distinguishing between enantiomers.

Transitioning into the realm of strong coupling, we explore the effects of moleculardisorder on the linear response of molecular polaritons. We provide analytical expressions for the vacuum Rabi splitting observed in the absorption, transmission, and reflection spectra under conditions of weak disorder, addressing multiple disorder distributions. Additionally, we introduce a novel sum rule offering a universal methodology for extracting accurate collective light-matter coupling values from experimental data.

Finally, we address the perplexing fact that classical linear optics can regularly describepolaritonic effects. We demonstrate that, in the thermodynamic limit, polaritonic transmission windows function as “optical filters”, and many phenomena attributed to polaritons can be replicated in bare molecular systems using appropriately configured linear optical sources. This insight urges a reevaluation of certain “polaritonic” phenomena and identifies promising directions for future research to uncover genuinely novel polaritonic effects.