Study On The New Method And Mechanism Of Magnetic Field Enhancement In Metamaterials

As is well known,the realization of optical magnetic field enhancement is as important as obtaining electric field enhancement in nanophotonics,due to its promising applications in magnetic nonlinearity and sensors.However,in the interactions of light with matter in the visible wavelength range,the role played by the magnetic component of light is usually negligible,since the force exerted by the electric field on a charge is much larger than the force applied by the magnetic field.Thus,exploring novel strategy to enhance the magnetic fields becomes very important.In this thesis,we first introduce some basic concepts,characteristics and latest research progress in the fields of surface plasmon and matematerials.We also propose and demonstrate two new methods for achieving optical magnetic field enhancement in metamaterials.The thesis is mainly composed of two sections that are arranged as following:1.We have proposed an alternative approach to realize strong diffraction coupling of magnetic plasmon(MP)resonances in metamaterials composed of two-dimensional(2D)arrays of metallic nanodisk pairs.We found that,through lifting the metamaterials to reduce the substrate effect,MP resonances supported in individual pairs of metallic nanodisks could strongly couple together with a collective surface mode propagating in the array plane,and thus result in a narrow-band hybridized mode.Associated with the excitation of this hybridized mode,the maximum magnetic field intensity within metallic nanodisk pairs is about 846 times of the incident field,and is enhanced to nearly 5.6 times larger than those at the purely MP resonance.More importantly,we also found that for such a diffraction coupling of MP resonances,the magnetic field of the collective surface mode must be parallel to the magnetic moment induced in the paired metallic nanodisks.2.We have theoretically investigated the magnetic field enhancement and Rabi splitting phenomenon at optical frequencies,because of the interactions between optical waveguide modes and magnetic resonances in metamaterials.The studied metamaterials consist of 2D arrays of Ag nanodisk pairs lying on a dielectric waveguide substrate.The plasmon near-field coupling between the upper and lower nanodisks in individual metallic nanodisk pairs results into magnetic resonances.The periodic arrangement of the paired metallic nanodisks can excite optical waveguide modes propagating in the adjacent dielectric waveguide.When optical waveguide modes are close to magnetic resonances by varying the array period,they interact to form two hybridized modes.A coupling model of two oscillators is also proposed to predict well the positions of the hybridized modes.In the strong interaction regime,the hybridized modes have a large anticrossing,and thus present Rabi splitting phenomenon.More importantly,the magnetic fields in the dielectric spacer between the upper and lower nanodisks exhibit a great enhancement,which may find promising potential applications in magnetic nonlinearity and sensors.