Browsing by Subject "Surface plasmon"
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Item Engineering metallic nanogap apertures for enhanced optical transmission(2016-10) Yoo, DaehanPhysics and technology of metallic nanoapertures have been of great interest in nanophotonics. In particular, enhanced optical transmission mediated by surface plasmon waves in metallic nanoapertures has been widely studied and utilized in biochemical sensing, imaging, optical trapping, nonlinear optics, metamaterials, and optoelectronics. State-of-the-art nanotechnology enables researchers to explore optical physics in complex nanostructures. However, the high cost and tedium of conventional fabrication approaches such as photolithography, electron-beam lithography, or focused-ion-beam milling have limited the utilization of metallic nanoapertures for practical applications. This dissertation explores new approaches to enable high-throughput fabrication of sub-10-nm nanogaps and apertures in metal films. In particular, we focus on a new technique called atomic layer lithography, which turns atomic layer deposition into a lithographic patterning technique and can create ultra-small coaxial nanoapertures. The resulting nanostructures allowed us to observe extraordinary optical transmission in mid-infrared regime that originates from an intriguing physical phenomenon called the epsilon-near-zero (ENZ) condition. Subsequently, we turn this nanogap structure into a high-Q-factor plasmonic resonator, called a trench nanogap resonator, by combining a nanogap and sidewall mirrors. This structure is optimized for electrical trapping of biomolecules and concurrent optical detection, which is demonstrated experimentally via dielectrophoresis-enhanced plasmonic sensing. The fabrication technique and resulting structures demonstrated in this thesis work can facilitate practical engineering of metallic nanoapertures towards harnessing the potential of plasmonics.Item Theoretic investigation on plasmonics of noble metallic nanoparticles(2013-08) Qian, XiaohuIn this thesis, we report our theoretic investigation on the surface plasmon polaritons of noble metallic nanoparticles and its applications. By means of numerical experiments, we studied the general far-field and near-field optical properties of the promising hollow metallic nanoparticles, the pattern of far-field extinction efficiency and the near-field surface-enhanced Raman scattering. We demonstrated the distribution of plasmon resonance wavelength as functions of the geometrical factor of hollow spherical gold and silver nanostructures. In addition, we utilized a novel mechanism of harnessing the mechanical strain to controllably tailor the plasmon-based optical spectra of single metallic nanospheres and the array of metallic nanoparticle of spheres and circular discs. The second goal of this thesis is to utilize a novel mechanical-strain-induced effect to enhance the light-trapping performance of plasmonic solar cells. This multi-physical scheme has the potential of considerably reducing the thickness of semiconductor layer and hence save the cost of production of the solar cells. Corresponding simulation results demonstrated this strategy is promising to decrease the fabrication budget of solar industry.