Spectroscopic Resonance Effects In Micro-Nano-Photonic Structures

Micro-nano photonics is an important branch of physics and optical engineering,which involves research topics in optics/optoelectronics and nanotechnology,and focuses its studies on the new physics or new physical phenomena and effects in the interaction in light-matter interaction under micro-and nano-scale.Some typical research fields include mechanisms involved in light-matter interaction and its applications in light generation,light propagation,optical manipulation,and photo-electronic detection.In particular,some photophysical resonance effects in nanophotonic structures have been extensively studied,including waveguide resonance modes,Fano coupling effects,and surface plasmons.The importance of these effects lies in the potential applications in bio-or chemical sensors,surface enhanced Raman scattering spectroscopy,solar cells.This thesis is centered around the realization of mirco-and nano-scale photonic structures/devices and the studies on photophysical resonance effects,including the following research works:?1?Preparation of mirco-/nano-scale dielectric and metallic grating structures and studies on related Fano resonance effectsWaveguide dielectric grating structures with different diffraction efficiencies were prepared by interference lithography.Fano-like coupling between the diffraction process and the second-order waveguide resonance modes was investigated.The diffraction efficiency of the gratings was enhanced by adjusting the duty cycles of the grating structures,which enhanced the Fano-like effect.This not only propose the basic principles for constructing devices with Fano-like coupling effects,but also gave insights into the physics of waveguide metallic photonic crystals,where the plasmonic scattering of light into waveguide can be verified to be the main mechanism.As the diffraction light increases,the waveguide mode gradually shifts from the extinction peak to the extinction valley,and the Fano coupling resonance occurs between the diffraction light and the second-order waveguide mode.The discovery for this Fano resonance shows that the mechanism of the Fano resonance in waveguide-coupled metal photonic crystals is scattering.Waveguide grating structures were fabricated in a single-layer ITO film and interaction between the second-order Bragg-like diffraction and waveguide resonance mode was studied.At a specific angle of incidence,these two processes were overlapped in their spatial locations and propagation directions.On this basis,the beam-splitting functions of such structures were studied,where both the splitting ratio and the working efficiency were optimized by adjusting the modulation depth of the grating and the thickness of the ITO waveguide layer.Furthermore,we deposited a thin layer of silver to cover the ITO grating.We studied the surface plasmon polariton performance in the silver shell and its Fano-like coupling with the resonance mode in the underneath ITO waveguide.For TM polarization,we observed Fano-coupling of the symmetric and asymmetric surface plasmon polaritons with the second-order waveguide resonance mode.?2?Bimetallic photonic structures and heterointerfacial plasmon resonanceUsing solution processed techniques,we proposed a new method for the fabrication of a bimetallic network consisting of gold nanoparticles and silver nanowires,where photoreduction technique was employed to produce silver nanowires from silver ions in a polymer film.Dipolar and quadrapolar plasmons were revealed in each gold nanoparticle and silver nanowire with large dimensions.Interaction between these resonance modes and the resultant heterointerfacial plasmons were studied.?3?Chemical synthesis of gold nanocups and studies on the multifold localized surface plasmon resonance effectsUsing the chemical synthesis technique based on the templated and seeded growth method,gold nanocup structures with controllable size and morphology were prepared.The factors and parameters influencing the growing process and the morphological control of the gold nanocups were investigated.Making use of the SiO₂ nanospheres and phenol formaldehyde resin coating as the template,we prepared gold nanocups with different sizes.In combination with the spectroscopic studies,we analyzed the photophysical nature of the localized surface plasmons in the gold nanocups,where the local-field and charge-carrier distribution were simulated accordingly.Furthermore,by varying the amount of the reaction solution,we have also prepared a series of nanostructures of gold nanocaps,gold nanocups,and gold nanoshells,and characterized the microscopic and spectroscopic performances.