| Because of the development of theoretical study and nanofabrication techniques, Surface plasmons (SPs) is widely used in the area of nanophotonics, gradually. Through decades of investments, SPs has been opened up magnetoplasmon, photovoltaic and many other new research fields. In this paper, we study the enhancement of Transversal Magneto-Optical Kerr Effect (TMOKE) and the application of perfect absorption by the numerical simulation of periodic metal microstructures.Magneto-optical effects have potential applications in biosensor, magneto-optical data storage, three-dimensional image and so on. In this paper, we propose that a periodic gold strips array is embedded into a magnetic dielectric film of bismuth iron garnet(BIG), which is supported by a quartz substrate. We numerically study the optical properties of our proposed microstructure and the corresponding evolution of the TMOKE responses due to the coupled optical modes dependent on the structural parameters. On the one hand, the polarized free-space incidence will be scattered to the waveguide (WG) mode propagating in the BIG film with the assistance of the periodic arrangement of gold strips and interact with BIG film abundantly which result in the enhancement of TMOKE response. On the other hand, the simultaneous excitation of LSPs of individual gold strip will couple with the WG mode in BIG film which will lead to a further enhancement of TMOKE response. As the embedded depth increases gradually, the coupling of the WG mode in BIG film and LSP mode of the individual gold stripe become much stronger and form a highly efficient Fano resonance, which leads to most of the electromagnetic field being localized in the BIG film and strong interaction with the BIG magnetic dielectric film, and thus, an enhancement of TMOKE response can be observed. We find that when embedded depth reach to 80nm, a strong TMOKE response can be achieved about 3 fold larger than the case that the gold strips in the surface of BIG film. Our study proposes a new method to realize the amplification of weak TMOKE response utilizing the plasmonic microstructure, which might be potential for the design of high-efficiency magneto-optical devices.SP-assisted enhanced optical absorption provides an available method to improve the interaction between incident light and active layer. In the last ten years, infrared quantum well infrared photodetectors (QWIPs) got a rapid development. According to the optical in-coupling strategies in n-type GaAs quantum well, only the electric field component which normal to plane of the quantum well layer can be absorbed by quantum well. In order to improve the response rate and detection rate of the quantum well device, we propose a highly efficient optical incoupler for enhancing the absorption of infrared light, which comprises of a thin top-contact/quantum wells/bottom-contact semiconductor layer sandwiched by a periodically corrugated gold back plate and an array of gold square micropatches. This metallic microstructure can support a microcavity mode and a hybrid spoof SPP (SPPs)mode. A great enhancement of absorption is achieved by the coupling of the microcavity modes and hybrid SPPs. we get an almost perfect absorption reach to 92% in the wavelength of 14.5um and 60% of the energy can be absorbed by the quantum well. Moreover, our designed nanostructure also has the advantages of polarization insensitive and a broad incident angle compatible which might be beneficial to the infrared focal plane arrays photodetectors. |
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