Research On One-way Guiding Of Electromagnetic Waves And Related Nonreciprocal Optical Components

The magneto-optical photonic crystal (MOPhC), which takes advantages of both magneto-optic effect and photonic crystal (PhC), has been becoming a hotspot in the field of PhC research. When a proper external magnetic field is applied onto the MOPhC, the nondiagonal elements of its dielectric tensor or permeability tensor can be changed such that gyroelectric effect or gyromagnetic effect will be induced. The presence of gyroelectric effect or gyromagnetic effect will break the time-reversal symmetry of the system, leading to the phenomenon of one-way electromagnetic wave transmission within the MOPhC. The nonreciprocal devices based on the one-way edge modes of MOPhC have great application potential in the fields of optical communications and optical integration chips.In this thesis, we first investigate the band properties of the two-dimensional MOPhC by applying the improved plane wave expansion method (PWEM), and the influence of different lattice types, structural parameters and external magnetic field intensities on them have been analyzed. Next, we investigate the guiding characteristics of one-way waveguides formed by the various edges of MOPhC with the supercell technique.On the basis of the above mentioned research, a new type of resonator structure (i.e., one-way PhC waveguide based resonator structure) is proposed. The coupling between the proposed resonator and the regular PhC waveguide is investigated, and a resonator-wave guide coupling system is designed based on the coupling theory. Profiting from the one-way edge mode of magneto-optical PhC, the proposed resonator structure possesses the characteristics of high quality factor, unidrectional coupling, and controllable one-way rotating direction. Simulation results show that the quality factor can be higher than105in the case when the structure is optimized.For the problem that the operating bandwidth, transmission rate and realization complexity cannot be simultaneously well treated in conventional beam splitter, in this thesis we propose Y-junction beam splitters and T-junction beam splitters based on one-way PhCs waveguide. The proposed beam splitters have simple structure and low manufacture requirement. In addition, it is proposed to control the power ratio between the two outputs by introducing a defect at a proper position in the splitter. Simulation results demonstrate that the proposed splitters are able to achieve almost100%transmission, have very large bandwidth and are prone to impedance matching.Finally, a new kind of one-way slab waveguide with much simpler structure is proposed. The proposed waveguide is formed only by a gyromagnetic material plate and air layer. Theoretical analysis shows that, by adjusting the thickness of the air layer, the electromagnetic waves at a certain frequency band can only propagate along one direction, resulting in one-way waveguide.In summary, some achievements with academic value and application prospects have been obtained on magneto-optical PhCs, one-way PhC edge mode and PhC-based nonreciprocal devices. Some exploration work has also been performed in designing new type one-way slab waveguide. The work of this thesis will help in making MOPhC technology and one-way mode waveguide technology feasible for practical applications.