  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, which depends on the number
of coupled molecules. We experimentally and numerically study the evolution of
photoemission from a thin layered J-aggregated molecular material strongly
coupled to a Fabry-Perot microcavity as a function of the number of coupled
layers. We unveil an important difference between the strong coupling
signatures obtained from reflection spectroscopy and from polariton assisted
photoluminescence. We also study the effect of the vibrational modes supported
by the molecular material on the polariton assisted emission both for a focused
laser beam and for normally incident excitation, for two different excitation
wavelengths: a laser in resonance with the lower polariton branch, and a laser
not in resonance. We found that the Raman scattered photons play an important
role in populating the lower polariton branch, especially when the system was
excited with a laser in resonance with the lower polariton branch. We also
found that the polariton assisted photoemission depends on the extent of
modification of the molecular absorption induced by the molecule-cavity
coupling.
