Student Seminar: Polaritons and Optical Filters

     Venue: Rajarshi Bhattacharyya Memorial  Lecture Hall, Chemical Sciences Building

Strong coupling between molecular transitions and optical modes in a Fabry–Pérot cavity, leading to the formation of hybridized light–matter states called polaritons, has been demonstrated to be an exciting route for controlling chemical reactivity and various other molecular properties^1,2. However, the field of polaritons has been marred by several contradictory findings^3,4.

To deepen the understanding of such systems, at a conference held in La Jolla, California, in 2023, theorists and experimentalists from two different camps sought to draw a clear divide between polaritonic phenomena that can be described solely through the language of classical linear optics and those that go beyond such a description, requiring the framework of cavity quantum electrodynamics⁵.

In my talk, I will discuss the modeling of polaritonic cavities through both linear optical and quantum-mechanical descriptions. I will present the work of Yuen-Zhou and co-workers, who exploit permutational symmetry to show that polaritonic phenomena can be approximated as optical filtering in the zeroth-order perturbative limit—thereby serving as a bridge between the two camps – classical optics and cavity-QED^5–7.

I will end by taking a slight detour to explain the classical optical description of pump–probe experiments inside a cavity⁸. Recent experimental works by Simpkins and Weichman groups on the spectroscopy of metal–carbonyl complexes within a cavity will be briefly explored^9,10.