| The influence of a magnetic field or magnetic moments on the interaction between light and substance, such as light reflection, refraction, plane of polarization or phases etc., is called the magneto-optical(MO) effect. Traditionally, MO effects were studied in homogeneous media. But now with the rapid development of technology, photonic crystals made of MO particles become more and more popular, and chiral edge states(CES) discovered in different structures have been extensively studied. While, localized surface plasmon resonance(LSPR) effect of MO particles offers a new mechanism for chiral edge states of two-dimensional MO photonic crystals. One-way waveguides based on LSPRCES exhibit better magnetic tunability and lower sensitivity to lattice disorder, which promises more possible applications in future.In chapter one, we give a brief introduction of recent developments in the research of magnetic optics, surface plasmon resonance and the LSPR of MO particles. The main contents and results in chapter two and three are displayed as follows:(1) Based on Mie theory, we have obtained the LSPR conditions and the electric field features by analyzing the details of scattering behaviors for the LSPR effects of a single MO particle. Compared with ordinary particles, we find the LSPR conditions will split due to the MO Voigt coefficient, which is observed not only between ?n peak and-n peak, but also between peaks of lower-order and higher-order. Another important feature is the simultaneous occurrence of the far-field resonance and the near-field resonance, where the latter is characterized by a peak of energy-flow circulation around the particle. Calculation on a particle of large size shows the size effect on the LSPR peaks, including shifted resonance frequencies, broadened resonant peaks, and emergence of higher-order peaks. Our results give a good explanation to the deviation between previous theory and experiments.(2) In this part we extend the LSPR effects of a single MO particles to those observed in photonic crystals(PC) consisted of MO particles. We replace the conventional line-defect adopted in MO-PC based waveguides by an artificial domain wall to study how LSPR effect affects the two-dimensional MO-PC composed of ferrite rods. We propose an effective-medium theory breaking the long-wavelength approximation, and obtain unidirectional domain-wall modes conditions theoretically. In numerical simulations, calculation of bands and the penetration depth as well as transmission spectra analysis explain the excellent unidirection and lower penetration based on localized surface plasmon-chiral edge state(LSP-CES) found in experiments. Also, it is verified that the edge state is widely tunable by applying the external magnetic field and immune to lattice disorders. Here, we put forward two new designs of applications based on LSPR-CES. One is a signal selector, which makes it possible that different signals export in different ports and the same signal can also export in different ports. The other is the multi-branch splitter, which is consisted of an entrance and one-to-three exports. The amount of the branches can be tuned by writing different magnetic patterns into the MO-PC. Also, we can regulate the power ratio of branches by means of altering the radius and index of refraction of the nonmagnetic cylinder in a cavity region introduced in the structure. |
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