Light Matter Interaction in Epsilon Near Zero Metal/Insulator Layered Nanocavities Thesis

Light-matter interaction has been a widely investigated phenomena enlarging the area of nanophotonics beyond the limit. This stand out to be the back bone for future generation optical devices. Light confinement and propagation in a small volume gives rise to several rich optical properties. This can be realized in different type of nanostructured materials. Metal(M)/Insulator(I) multilayer nanocavities are highly versatile systems for light confinement and wave guiding at nanoscale. Their physical behavior is discussed successfully by electromagnetic theory. However, it is still obscured about the nature of cavity modes in layered metal/insulator nanocavities. The reason why such cavity mode can be excited without having any momentum matching technique are yet to be investigated. We start with a quantum treatment of the MIM as a double barrier quantum well where the resonant modes are assisted by tunneling of photons. The lossless characteristics of these modes with zero wavevector condition are inherent to the epsilon-nearzero (ENZ) band. We further investigated the coupling between epsilon near zero assisted volume plasmons in MIMIM nanocavities where one MIM cavity placed above the other. Strong coupling has been demonstrated in this system by an anticrossing of the ENZ modes in the individual cavities, where the splitting depends strongly on the thickness of the central metal layer. The properties of ENZ bulk plasmon modes for MIM and MIMIM systems are exploited to achieve both enhancement of spontaneous emission and decay rate of the perovskite nanocrystal film placed on the top of the nanocavity. However, the enhancement is within the limit of weak coupling regime. In order to achieve strong coupling between ENZ mode of cavity and emission mode of the fluorophore, one need to embed the fluorophore inside the cavity. But it has been realized that in such a case, long term stability of fluorophore by retaining its original optical properties are primary challenges. We studied the optical properties of nanocrystal layer that were overcoated with alumina by atomic layer deposition. This enabled us to effectively embed the NCs inside the dielectric layers of planar MIM and MIMIM nanocavities.