Ultra hızlı ışık modülasyonu için manyetooptik malzemeler ve cihaz mimarileri

Magnetooptical (MO) Faraday and Kerr effects lead to rotation of the polarization plane of light in interaction with a magnetized matter. In combination with the intrinsic high speed of magnetization reversal which can go down to femtosecond time scales, MO effects enable magnetooptical spatial light modulators (MOSLMs), promising for nonvolatile, ultrafast, and high-resolution spatial modulation of light. The recent developments in low-power magnetization switching bring about major breakthroughs in MOSLMs benefiting beyond state-of-the-art holography, heads-up displays, virtual and augmented reality systems, data storage, optical communications, solid-state light detection and ranging (LIDAR), and emerging optical devices. The inherent weakness of the MO effects and difficulty in producing high-quality MO materials are the main obstacles on the way of the practicality and industrial development of the MOSLMs. This thesis addresses the challenges associated with MOSLMs and introduces novel solutions for realizing practical MO devices. The advancement of MOSLMs in different aspects including materials engineering, driving system, and device architecture is reviewed in the thesis to locate the present state in this research field. The MO figure of merit for various MO materials reported in the literature is calculated and compared using finite-difference time-domain (FDTD) simulations, suggesting bismuth-substituted yttrium iron garnets (Bi:YIG) with Bi1Y2Fe5O12 composition as the superior MO component for MOSLMs. Growth of Bi:YIG thin films on different substrates, by pulsed laser deposition using different growth parameters, is studied in order to optimize the growth conditions. The structural and optical characterization of the Bi:YIG films reveal the accomplishment of epitaxial growth on the garnet substrates and growth of poly-crystalline single-phase films on quartz substrates. In addition to the study of the materials prospect, photonic devices for the enhancement of MO effects are designed. Various magnetophotonic crystal (MPC) structures are investigated for high-contrast MOSLMs. By optimization of the MPC configuration and layer thicknesses, a three-defect MPC is demonstrated capable of simultaneous enhancement of Faraday rotation at three fundamental wavelengths of red, green, and blue (RGB) within a pixel. Rotation values of 20-55° are achieved in an overall thickness smaller than 1.5 μm including submicron garnet layers, whereas the optical loss is retained below 20 dB. The resonant approaches for enhancing the MO effects generally result in a narrow operation band and limit the applications. In this study, a magnetoplasmonic metasurface is designed for the broadband enhancement of the Faraday effect. While Faraday rotation in a bare Bi:YIG film is below 0.02° in the studied range of 600-1600 nm, the proposed metasurface yields few degrees of rotation in a broad spectral range, with a maximum exceeding 6.5°. It is shown that the MO response of the metasurface and the operation band can be further improved by optimizing the geometry and excitation parameters, leading to rotation values higher than 20° for a total thickness of 15 nm. Finally, the guidelines for designing a desired magnetoplasmonic metasurface are presented and the application of plasmonic metasurfaces in sensing systems is discussed. Different metasurface designs are modeled, fabricated, and tested for surface-enhanced Raman spectroscopy (SERS) and enhancement of the Raman signal by over three orders of magnitude is experimentally demonstrated.