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Enhancement of magneto-optical properties in magnetic photonic crystal slab waveguide based on yttrium iron garnet
摘要： In this work, a polarization-independent waveguide based on magnetic photonic crystal (MPC) with a triangular lattice of air holes in Yttrium Iron Garnet (YIG) slab grown on alumina (Al2O3) substrate is proposed, where both TE-like and TM-like periodic band gaps overlap. YIG is well known for its attracting magneto-optical (MO) properties and used to produce a coupling between the TE and TM modes. Thus, a nonreciprocal effect can be obtained by applying an external magnetic field parallel to the direction of propagation. At 1550 nm, the complete photonic band gap is simulated and optimized using the three dimensional plane-wave expansion method. The aim of this study is to enhance Faraday rotation (FR) while maintaining a low modal birefringence. A numerical analysis in function of magnetic gyration (g) has been reported, using the BeamProp software. The results reveal a proportional relation between FR, ?n and g, such for g = 0.5, a large FR of 26.11×104 °/cm with ?n = 7×10–6. The results show a real improvement of this MPC structure based on YIG with larger FR, lower modal birefringence and minimal losses. The notable enhancement in the MO behaviour could improve the performance of optical isolators, and makes it suitable for nonreciprocal devices.
关键词： modal birefringence,magneto-optical properties,Yttrium Iron Garnet,Faraday rotation,magnetic photonic crystal
更新于2025-09-23 15:19:57
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Cellulose-Based Microparticles for Magnetically Controlled Optical Modulation and Sensing
摘要： Responsive materials with birefringent optical properties have been exploited for the manipulation of light in several modern electronic devices. While electrical fields are often utilized to achieve optical modulation, magnetic stimuli may offer an enticing complementary approach for controlling and manipulating light remotely. Here, the synthesis and characterization of magnetically responsive birefringent microparticles with unusual magneto-optical properties are reported. These functional microparticles are prepared via a microfluidic emulsification process, in which water-based droplets are generated in a flow-focusing device and stretched into anisotropic shapes before conversion into particles via photopolymerization. Birefringence properties are achieved by aligning cellulose nanocrystals within the microparticles during droplet stretching, whereas magnetic responsiveness results from the addition of superparamagnetic nanoparticles to the initial droplet template. When suspended in a fluid, the microparticles can be controllably manipulated via an external magnetic field to result in unique magneto-optical coupling effects. Using a remotely actuated magnetic field coupled to a polarized optical microscope, these microparticles can be employed to convert magnetic into optical signals or to estimate the viscosity of the suspending fluid through magnetically driven microrheology.
关键词： magneto-optical properties,polarized light,cellulose nanocrystals,microfluidics,microparticles
更新于2025-09-11 14:15:04
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Optical and Magneto-Optical Properties of Multilayer Nanosized [Co/TiO2]n Films
摘要： The optical and magneto-optical properties of the metal–dielectric multilayer [Co/TiO2]n structures with 2–4-nm-thick layers prepared on a silicon substrate Si(001) by ion-beam deposition have been studied. The complex permittivity of multilayer [Co/TiO2]n structures has been measured by the optical ellipsometry technique in the spectral range of 0.6–5.6 eV and analyzed using the optical reflection matrices for isotropic multilayer dielectric structures taking into account the optical losses and also using the method of anisotropic effective medium. The magneto-optical Kerr effect has been measured by the polarimetric technique in the spectral range of 1.2–4.5 eV in the polar and longitudinal geometries. The magnetic anisotropy type is determined on the base of the field dependences of the magneto-optical Kerr effect. It is found that the nanosized [Co/TiO2]n structures can be considered as artificial optically uniaxial media with a strong magnetic and optical anisotropy at room temperature.
关键词： silicon substrate,Co/TiO2,magneto-optical properties,multilayer nanosized films,optical properties,complex permittivity,magneto-optical Kerr effect,magnetic anisotropy,optical ellipsometry,ion-beam deposition
更新于2025-09-10 09:29:36
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Fabrication and magneto-optical properties of TGG transparent ceramics
摘要： Terbium gallium garnet (Tb3Ga5O12, TGG) transparent ceramics were synthesized by the co-precipitated method and vacuum sintering with MgO as sintering aids. Samples sintered at 1500℃, 1550℃ and 1600℃ for 20h were utilized to examine the phase compositions, optical quality, microstructure and magneto-optical property. X-ray diffraction (XRD) results show that the three samples have pure garnet crystal structure. The sample sintered at 1550℃ shows high transparency and the optical transmittance is close to 80% in the region of 500-1500 nm. SEM micrographs demonstrate that the sample sintered at 1550℃ exhibit best microstructure and the average grain sizes were 5.32 μm. The Verdet constant of the samples were investigated in detail at different wavelength and temperature. The results indicated that TGG ceramics can meet the demand for magneto-optical devices in the visible-near infrared region.
关键词： Faraday effect,Magneto-optical properties,TGG ceramics,Optical materials
更新于2025-09-10 09:29:36
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Quantum behavior of hydrogen-vacancy complexes in diamond
摘要： Hydrogen plays an essential role in the growth process of artificial diamond and can easily form complexes with lattice vacancies. Despite substantial efforts to resolve the electronic structure and the ground-state properties of the hydrogen-vacancy (HV) center, the final remarks are ambiguous, while the complexes of vacancy with two and more hydrogen atoms remain unexplored. In this paper, we used spin-polarized, hybrid density-functional theory method to investigate electronic structure and magneto-optical properties of various hydrogen-vacancy clusters in diamond. Our theoretical results indicate a very strong tendency toward the formation of HnV complexes up to four hydrogen atoms that are mostly electrically and optically active centers. One of the investigated defects introduce highly correlated electronic states that pose a challenge for density-functional theory and, therefore, require special treatment when charge- and spin-density-related properties are determined. We introduced an extended Hubbard model Hamiltonian with fully ab initio provided parameters to analyze the complex electronic structure of highly correlated H2V0 defects. The role of quantum tunneling of hydrogen in HV center and its impact on the hyperfine structure was discussed. We demonstrate that experimentally observed HV1? center is similar to well-known NV1?, i.e., I) it possesses triplet 3A ground state and 3E excited state in C3v symmetry; II) the calculated zero-phonon line is 1.71 eV (1.945 eV for NV1?). A detailed experimental reinvestigation based on optically detected electron paramagnetic resonance spectroscopy is suggested to verify whether the HV1? center has metastable singlet shelving states between the ground and excited state triplets and, as a result, whether it may exhibit a spin-selective decay to the ground state.
关键词： quantum tunneling,diamond,hydrogen-vacancy complexes,magneto-optical properties,density-functional theory,quantum behavior
更新于2025-09-09 09:28:46