Abstract
Metamaterials are artificial structures made of the repetition of subwavelength elements, often used in controlling and engineering the electromagnetic behavior of light as effective media due to quasi-static approximation. Metallic metamaterials are objects of high interest due to their ability to show resonances in the optical response given by the collective behavior of the conduction electrons near the surface of the metal, the so-called surface plasmons. These resonances depend strongly on the optical properties and geometry of the structures, providing a versatile tool to sensing surrounding information beyond conventional sensors. In this dissertation, we design a four-cut split ring resonator (4CSRR) performing plasmonic resonance in near infrared (NIR) region, supporting the capability in detecting their surrounding refractive index changes. A 4CSRR array is further utilized in refractive-index imaging application with quantitative, label-free ability and coupler-free measurements. By modifying a hydrogel (Carboxymethyl Cellulose)-poly-l-lysine mixture on 4CSRR-array to increase the surface adhesion and water retention for culturing cell, an in vivo intracellular observation is demonstrated due to the extension of cellular survival time. In addition, a compact multi-resonant plasmonic split ring resonator (MPSRR) array that is designed, for utilizing in both multi-band plasmonic resonance-enhanced vibrational spectroscopy and refractive index probing within a bandwidth of several octaves. Such a single-element plasmonic metamaterial can be used as a multifunctional sensing pixel that enables mapping the distribution of targets in thin films and biological specimens by enhancing the signals of vibrational signatures and sensing refractive index contrast. The low-order resonant modes in MPSRR present short-range detecting depth but high localized field for demonstrating plasmon-enhanced vibrational spectroscopy on the interface between target and MPSRR; in contrast, the high-order resonant modes exhibit long-range detecting ability with refractive index sensitive for realizing intracellular refractive index contrast observation. These unique features enable the plasmonic metamaterials to function as a rapid and accurate diagnosis, facilitating bio-sensing and imaging capabilities. Next, to improve the resonant performance for the development in sensors, we apply dielectric-based metamaterial to provide control of the far-field radiation properties of nearby emitters due to the properties of coherent radiation of electric and magnetic modes. Unlike resonating plasmonic metamaterials are producing the oscillations of the free electron plasma, dielectric-based metamaterials rely on the fields and displacement currents induced in the resonator structure. In addition, we develop a Fano-resonant metamaterial by using dielectric-resonator dimers. By hybridizing two types of dielectric resonators, identical-dielectric-constant resonator dimer (IDR) and distinct-dielectric-constant resonator (DDR) dimer, respectively, we demonstrate Fano-resonance phenomena associated with a large group index (ng~354) and significant enhanced electromagnetic fields. Along this analysis, a comparison with metallic dimers has been carried out. This study opens new possibilities to perform field-enhanced spectroscopy and sensing with nanostructures made of suitable dielectric materials. Last, to control and investigate the resonant behaviors in dielectric-based metamaterial in mid infrared region, a highly symmetric dielectric metamtaterial is designed by germanium-based resonators array embedded with thermal-controlled functionality (vanadium dioxide, VO2). There are two distinct resonances respectively excited from particle and particle-substrate coupling. An enhanced reflectance change of resonant spectra occurs while raising temperature upto the VO2 phase-transition region, realizing the tunable resonances in mid infrared region. The tunibility significantly depends on the conductivity of vanadium dioxide layer, which agrees well to the simulation results. These results match to the model of an equivalent parallel RLC circuit, opening the feasibilities of optical sensing, artificial magnetism, perfect absorber and invisible cloak.