Nonlinear exciton-polariton dynamics through classical and quantum spectroscopy

Exciton-polaritons are bosonic quasi-particles generated through the strong coupling of optical excitations in a semiconductor with a resonant mode of a microcavity. While the exciton-polaritons enable manifestation of collective quantum phenomena, the emergence of coherent dynamics of polaritons essential to drive such processes is dependent on their nonlinear many-body interactions. Here we will discuss the dynamics of such interactions measured through nonlinear optical probes based on ultrashort optical pulses in strongly-coupled microcavities made of organic molecules and those that are based on two-dimensional metal halides. In addition, we present an alternative methodology reliant on spectrally entangled biphoton states as a probe of such many-body dynamics.