As the nanodisk diameter is increased, the MIM metasurface resonance is redshifted towards the spectral region of the different molecular vibrational modes and gradually begins to overlap with them. This is accompanied by an absorbance enhancement from vibrational modes by up to a factor of 50. When coupling comes into effect the polyimide molecular vibrational modes undergo hybridization with the plasmon resonance of MIM metasurface, leading to clear spectral shifts and splittings. Initially, when a polyimide peak is situated in close vicinity to the MIM mode, it gets slightly redshifted from its respective intrinsic molecular vibrational mode position. However, when plasmonic and vibrational modes overlap particularly strongly, peaks instead undergo a blueshift. These two stages are respectively termed the weak coupling and the strong coupling regime, as categorised by A. F. Kockum, et. al. . The coupling strength is classified as strong or weak based on whether the light-matter coupling strength g is sufficiently large to exceed the losses in the system or not. The weak coupling regime is associated with the Purcell effect, responsible for a variety of photonic phenomena such as fluorescence enhancement, surface-enhanced Raman scattering (SERS) and surface-enhanced infrared absorption (SEIRA). On the other hand, the signature characteristic of strong coupling are vacuum Rabi oscillations that can manifest as an energy splitting in the dispersion relation .