Light emission from nanoscopic sources is used in many fields of fundamental and applied research, such as nanophotonics, quantum information technology and medical diagnostics. Diamond color centers are photostable single-photon sources with optically tailorable and readable spin of long coherence time at room temperature. Nitrogen (NV) and silicon (SiV) vacancy are widely studied representatives of color centers. For effective quantum information applications, their luminosity and polarization contrast need to be increased and their lifetime need to be reduced. The emission properties of single-photon sources are affected by their environment. Localized surface plasmons are electron plasma oscillations, which can be resonantly excited on a nanoparticles smaller than or comparable to the operation wavelength. The nanophotonic environment can be modified by placing a properly designed individual plasmonic nanoresonator near the emitter. The resonance frequency and impact including the intense near-field enhancement, lifetime reduction via Purcell phenomenon and quantum efficiency increase by radiative decay fraction modification depend on the size, shape, and material properties of the nanoresonator.
In the PhD thesis, I have modified and improved the numerical environment based on a finite element method to determine the optical response, namely the enhancement of excitation and spontaneous (non-cooperative) emission of a NV or SiV color center coupled to an arbitrary individual nanoresonator.
Integrated with a robust optimization algorithm, GLOBAL, the method is suitable for maximizing the fluorescence enhancement of color centers through geometry tuning under desired conditions, by simultaneously improving the excitation and emission processes in demand. The in-house developed numerical method has been applied to optimize the geometry and configuration of nanorod and core-shell monomer or dimer coupled color center systems and to maximize their fluorescence. The optical response of the optimized systems has been a subject of a detailed analysis by determining the Purcell factor, quantum efficiency, radiative enhancement spectra, as well as the charge, near-field and far-field distributions to identify and analyze the properties of the contributing plasmonic modes.