Doctor of Philosophy (PhD)
Electrical and Computer Engineering
In this dissertation, we show numerically that a compact structure, consisting of multiple optical microcavities at both the entrance and exit sides of a subwavelength plasmonic slit, can lead to greatly enhanced directional transmission through the slit. The microcavities increase the resonant enhancement of the emission in the normal direction and/or the coupling between free space waves and the slit mode. An optimized structure with two microcavities on both the entrance and exit sides of the slit leads to ~ 16 times larger transmission cross section per unit angle in the normal direction compared to the optimized reference slit without microcavities. We then introduce highly-compact resonant-cavity-enhanced magneto-optical switches for metal-dielectric-metal (MDM) plasmonic waveguides. The static magnetic field induced asymmetry, which enhances or reduces the coupling between the waveguide and a side-coupled resonator, and the relatively large induced wave vector modulation are used to design a Fabry-Perot cavity magneto-optical switch, consisting of a MDM waveguide side-coupled to two MDM stub resonators. The on and off states correspond to either the presence or the absence of the externally applied static magnetic field. We then investigate the influence of Rabi splitting tuning on the dynamics of strongly coupled J-aggregate/surface plasmon polariton systems. In particular, the Rabi splitting is tuned by modifying the J-aggregate molecule concentration while a polaritonic system is provided by a nanostructure formed by holes array in a golden layer. From the periodic and concentration changes we identify, through numerical and experimental steady-state analyses, the best geometrical configuration for maximizing Rabi splitting, which is then used for transient absorption measurements. We finally study the combination of scanning probe technology with photonic nanojets. Here, by using advanced 3D fabrication techniques we integrate a microbead on an AFM cantilever thus realizing a system to efficiently position nanojets. This fabrication approach is robust and can be exploited in a myriad of applications, ranging from microscopy to Raman spectroscopy. We demonstrate the potential of portable nanojets by imaging different sub-wavelength structures. We also show that finite-difference time-domain (FDTD) simulations are in good agreement with experiments.
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Haddadpour, Ali, "Microcavity Enhanced Beaming and Magneto-Optical Switching of Light" (2017). LSU Doctoral Dissertations. 4434.