Spectroscopic Studies On The Waveguided Metallic And Dielectric Photonic Crystals

Waveguided metallic photonic crystals are a kind of metamaterials that are composed of dielectric waveguide and periodically arrange metallic micro- or nano-structures. Compared with the dielectric waveguide grating structures, waveguided metallic photonic crystals exhibit remarkable and unique optical properties which are characterized by the strong anti-crossing behaviors between the waveguide resonance modes and particle plasmon resonance. Therefore, they may be widely applied in biosensors, gas sensors, optical switchs, solar cells, distributed feedback lasers, and polarization filters. In this thesis, the studies on wavegudied metallic photonic crystals are focused on the following aspects: (1) Exploring the intuitive photophysical mechanisms behind the optical properties of waveguided metallic photonic crystals; (2) Extending the photophysical mechanisms for the coupling between the waveguide resonant modes and particale plasmon resonances into universal models; (3) Integration of waveguided metallic photonic crystals with the optical fibers, bringing about flexbile applications in some extreme conditions.A review on the optical properties, fabrication methods, and practical applications of the metallic photonic crystals is given at the beginning of this thesis. In particular, the background of waveguide grating structures is introduced in detail, which is the basis for the physics and applications of the waveguided metallic photonic crystals and constitutes the fundamentals for all of the theoretical and experimental works in this thesis.Based on the theory of dielectric planar waveguides, the rigorous coupled-wave analysis method, the Ray Picture model, and the experimental results, the tuning properties of the resonant mode of the waveguide-grating structures as a function of the structural parameters are investigated systematically. This intends to give a comprehensive photophysical picture of the waveguide grating structures. The theoretical results show that using the TM polarization and large incident angles are very effective in improving the response sensitivity of the waveguide grating srtuctures to the environmetal changes and are thus important in the applications of this kind of nano devices in sensors. Furthermore, experimental studies found that the optical response of the waveguided metallic photonic crystals can be enhanced by the doubly waveguiding configuration.Considering that there exists close similarity between the waveguide dielectric grating and the waveguided metallic photonic crystal structures in the geometric configuration, however, particle plasmon resonance is the key mechanism for the unique physics in waveguide metallic photonic crystals, a reasonable modification is made to the Ray Picture model that applies to the dielectric waveguide grating structures, so that an analytical model is established for the theoretical studies on the waveguided metallic photonic crystals. Thus, the anti-crossing coupling between the waveguide resonance mode and particle plasmon resonance can be interpreted intuitively as the destructive interference between the directly transmitted light and the further diffractions of the propagation modes in the waveguide, which depends strongly on the intensity difference between the light involved in the two processes.Actually, particle plasmon resonance is not the only mechanism that supports the anti-crossing coupling effect. Even under the TE polarization, where no particle plasmon resonance is excited, the anti-crossing effect can also be obtained through changing the thickness of the metallic nanostructures, which consequently changes the difference between the transmitted and diffracted light intensity. This is important for a clear photophysical picture and for the applications of the waveguide metallic photonic crystals.Furthermore, waveguided Fabry-Perot (FP) microcavity arrays are introduced as a kind of new photonic device with tunable and narrow-band spectroscopic response. Theoretical studies show that the waveguide resonance mode and the FP microcavity resonance mode interact with each other through an anti-crossing coupling effect. This not only verifies the photophysical mechanisms proposed for the waveguided metallic photonic crystals, but also gives rise to a universal model for the waveguided photonic structures. Thus, combination of a single or multiple waveguide layers with periodically arranged nanostructures may be used as guidance for the design of photonic devices with sensitive spectroscopic response.Finally, fabrication of waveguide grating structures and waveguided metallic photonic crystals on the end facets of optical fibers has been achieved, which enables development of biosensors with the fibers used to deliver light and the detection unit consisting of photonic structures integrated on the end of the fiber. Optical spectroscopic characterization indicates excellent performance and thus potentially promising applications of this kind of device. This kind of configuration implies advantages of compactness, portable device, remote detection, and high anti-disturbance capability, which provides effective approaches for the sensor detection under extreme conditions of small working space, inaccessible locations, high temperature and high pressure, and harmful or toxic substance to be detected.