Electromagnetic Transmission Properties Of Dual-metallic Grating Structures And The Potential Applications

Subwavelength metallic slit (aperture) arrays attract great interest and extensive study, due to the extraordinary transmission phenomenon caused by the excitation of surface plasmon polaritons, which has potential applications in Photonic integrated circuit, photonic control technology, optical logic device and so on. Single metallic grating has been studied in detail, and dual-grating structure has been investigated theoretically and experimentally. Our group investigated the electromagnetic transmission properties of dual-metallic grating (DMG) structure and analyzed the high transmission and the transmission suppression (TS) phenomenon. This thesis discuss the electromagnetic transmission properties of dual-metallic grating composed of single metallic gratings (SMG) of different thickness under perfect electric conductor condition. The transfer matrix method is used as the algorithm, which has the advantages of simpleness and time-saving. Due to the specific electromagnetic properties of the DMG structures, the optical diode and the reflex optical sensor are proposed.Chapter I gives the introduction of extraordinary electromagnetic transmission. Various subwavelength structures are investigated, such as multilayer grating structures. The interested spectral regime is expanded from visible regime to microwave regime, in which unique properties are observed. At the end of this chapter, we give a summary regarding to the electromagnetic properties of the DMG structures in infrared and visible regimes in our group.Chapter II describes the Transfer Matrix Method (TMM), which is used to calculate the transmission property of the multilayer metallic grating structure in detail. Compared with other algorithm, TMM is simple and time-saving. We modify TMM, according to the actual conditions. When two SMGs, which construct the DMG structure, have different thicknesses, we rewrite the formula in infrared and visible regimes.ChapterⅢinvestigates the transmission properties of DMG by using TMM. With the transmission spectra and the field distributions, the mechanism of the high transmission is revealed. TS lines are observed in transmission spectra, which are independent of the thicknesses of SMG. Based on the field distributions, a simple model is proposed to understand the TS phenomenon, and an analytic expression is developed as functions of wavelength, longitude separation and lateral displacement.Chapter IV proposes an optical diode based on the TS phenomenon of DMG. We predict the unidirectional optical transmission in the dual-metal grating structures composed of two gratings with different periods, in the absence of anisotropy and nonlinearity. The results indicate that under normal incidence, all the diffracted orders of the transmitted waves could be completely suppressed in a direction, while could be highly transmitted in the opposite direction. By choosing the pertinent grating thickness, period, and surface structure of gratings, such a structure exhibits zero-order nonreciprocal transmission (suppression) behavior.Chapter V focuses on a reflex optical sensor based on DMG with high angular sensitivity. The competition between the F-P resonance and the diffracted evanescent wave coupling in the DMG structure results in the specific reflection properties in certain range of longitude separation. When the refractive index of the material in the separation has a little change, the zero-reflection incident angle exhibits a large shift, implying that such a reflex optical sensor possesses high sensitivity. The reflex sensor has potential applications in biomolecule detection and monitoring of biochemical reaction.