Design And Manipulation Of Surface Plasmon For Photovoltaic And Sensing Devices

Surface plasmon is a coherent oscillation of the surface conduction electrons excited by electromagnetic (EM) radiation, which can produce tightly localized and huge enhanced field under resonance. With the rapid development of nano-science and nano-technology, plamonics emerges as a flourishing new field that can manipulate light at the nano-scale through exploiting the unique optical properties of subwavelength metallic nanostructures. It is also classified as an important part of nanopthotonics. Generally, localized surface plasmon (LSP) and surface plasmon polaritons (SPPs) are two kinds of familiar plasmons with different propagating properties. It is well known that the resonance frequency, field localization, field distribution, radiation of plasmonics can be readily controlled by the morphology, component, size of the nanostructure and the gap between subwavelength structures as well as the surrounding environment. As a consequence, plasmonics can be not only adopted to manipulate the light-matter interaction in the nano-scale for the fundamental research, but also have a great applications in photo voltaics, fluorescence enhancement, surface enhanced Raman scattering (SERS), surface enhanced infrared, environmental sensor, photo-detectors, nano-laser and optical antenna. Moreover, plasmonics is of great promising element for the smart and fast integrated circuits in the future. In this dissertation, we focus on the manipulation of the surface plasmon through delicate design of metallic nanostructures and its applications on the plasmonic solar cell, environmental sensing and electromagnetically induced transparency. The contents of the dissertation are outlined as follows.In chapter one, we first introduce the basic knowledge of surface plasmon and the plasmon hybridization theory, and then summarize the great achievements and applications of plasmonics. Meanwhile, we also present some challenges of plasmonics for the future. Lastly, we briefly introduce the method of Finite Difference Time Domain (FDTD), which is an important tool for numerical modeling and simulation in our study.In chapter two, we designed a novel optical layer mediated plasmonic solar cell, by combining plasmonic nanostructures integrated with an optical layer. Our proposed solar cell is provided with synergistic effects of the plasmonic forward scattering and field enhancement, and favorable redistributions of light field in the device due to interference effect mediated by optical layer. The new design optimizes not only the field distribution in device, but also with a good match between active layer absorption an AM1.5solar spectrum, achieving broadband absorption enhancement and maximum Jsc=11.1mA/cm2and Jsc enhancement factor EF=1.67. The new design is also of good compatibility with structure parameters, with nice Jsc enhancement above50%over large region.In chapter three, we demonstrated Fano interference and high-performance sensor with nanobar/silica/metal mirror structure. Fano resonance is realized by the out-plane coupling between LSPR of nanobar and SPPs in the interface of silica/metal mirror. This novel design can circumvent the trouble of stringent gap size fabrication in the conventional in-plane coupling with different resonant modes. The modes overlap, coupling strength and the line shape of Fano resonance can be readily controlled by the variation of nanobar size and array period. The sensitivity of this plasmonic system can reach936nm/RIU by SPPs mode, and the figure of merit (FoM) of LSPR sensing is as high as10.42, which is much higher than the conventional LSPR-based sensors,In chapter four, we realized the electromagnetically induced transparency (EIT) with a nanostructure pattern comprising of nanobar and U shaped split-ring resonator (USRR). With the near-field analysis, we find that EIT is induced by the coupling of electric dipole in nanobar and the magnetic dipole in USRR. The mechanism is distinctly different from the previous reported EIT, which frequently comes from the coupling between the electric dipole and the quadrupole. Therefore, the transmission width and depth of EIT in our case can be expediently controlled and manipulated by the gap size and in-plane displacement in the plasmonic structure.In chapter five, we present a brief outlook and prospect of plasmonics, including plasmon propagating loss, active modulation of plasmonic and magnetic resonance in optical frequency.