Nanostructured metals for enhanced light-matter interaction with nanoscale materials: design, sensing and single photon emitters




Sharifi, Zohreh

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Plasmonics have been used to enhance the interaction of light with metallic nanostructures and lanthanide-doped upconversion nanocrystals. This enhancement can be achieved by using specific structures, materials, and plasmonic resonators at the emission and absorption wavelengths of the particles. This dissertation is based on four projects, which are mainly about the interaction of light and matter in metallic nanostructures and the up-conversion of nanocrystals using plasmonic resonators. In metal-insulator-metal systems, the cavity's resonant length is determined by the plasmon wavevector and the phase of reflection from the end faces. In general, the resonance length is not a simple multiple of the half-wavelength due to the significant reflection phase. As a result, in order to have a better understanding of MIM cavity resonances, the reflection phase must be calculated correctly. In the first project, the reflection phase obtained by SPPs upon reflection off the slit end-faces is calculated analytically using a simple mode matching model for real metals showing both dispersion and loss. The technique is similar to previous works, with the exception that we use the unconjugated version of the orthogonality relation. The results show good agreement with the experimental data. By having a strong grasp of the SPP dispersion, this technique aids in the design of plasmonic devices for operation at a specific wavelength. Single-photon sources are optical sources capable of emitting a single photon. A single lanthanide ion within a plasmonic nano structure with a large emission enhancement is one technique to generate a single-photon source at 1550 nm, which is a low-loss band used in fibre optics. In the second project, plasmonic double nanohole resonators are fabricated using colloidal lithography. These structures have been used to enhance the emission from low-concentration erbium emitters. The results indicate that different levels of emissions exist based on the amount of Er contained inside the nanocrystals. These findings would be an excellent starting point for developing a single-photon source operating at a 1550 nm wavelength employing erbium. Because not only can it increase the emission rate from erbium emitters, but it also helps to find and isolate a single emitter, which gives a stable single photon source. Because the surface plasmon resonance is exponentially coupled to the surface, it exhibits excellent sensitivity to changes in the refractive index near the surface. This is the underlying principle of commercially available surface plasmon resonance biosensors. Due to the wide range of applications in water quality testing and biosensing, it is critical to developing highly sensitive sensors that are compatible with commercial sensors. In the third project, we develop a design for SRSP sensing using a rectangular stripe grating and a 10 nm thick gold film. The 10 nm gold layer is sufficiently thick to enable continuous films to be formed using standard deposition procedures. We demonstrate that by employing rigorous coupled-wave analysis, the surface sensitivity of these films to an adlayer is increased by 3.3 times in angle units and the resolution is increased by fourfold while working at the commercial SPR system wavelength of 760 nm. Before trapping a particle in double nanohole apertures, we must first locate the double nanohole on the sample (gold on glass with apertures) and compare the scanning electron microscopy images with the image on the camera in the optical setup using certain markers. In the fourth project, to make DNH aperture trapping easier, we provide a polarization and transmission dependency approach for localizing and orienting DNHs on a substrate. This method provides a time and cost-effective way to ease the experimental process. This technique may also be used to localize different aperture clusters and single holes.



Plasmonic, Nanostructures, Slit in a real metal, Optical tweezers, Single photon sources