研究目的
Investigating the modification of the magnetic dipole resonance of a silicon nanosphere illuminated by a focused azimuthally polarized beam induced by a metal substrate.
研究成果
The interference of the MD and its mirror image induced by the metal substrate is responsible for the dramatic narrowing of the line width from ～ 53 to ～ 20 nm. The sharp MD resonance in the scattering spectrum of the Si NS may find applications in nanoscale sensing with high sensitivity and color display with improved chromaticity and spatial resolution.
研究不足
The studies on the scattering properties of Si NSs illuminated by using focused AP beam are suspended in the air or placed on SiO2 substrate. The line widths of the MD resonances of such Si NSs still not satisfied for the practical applications where MD resonances with narrow line widths or large quality factors are highly desirable.
1：Experimental Design and Method Selection:
The scattering spectra of the Si NSs were calculated by using the finite-difference time-domain (FDTD) method. The electric field of the AP beam at the focal plane was calculated by the k-space beam profile definition and then used for the FDTD simulation.
2：Sample Selection and Data Sources:
The radius of the Si NS was fixed at R = 100 nm, and the metal substrate was chosen to be a perfect electric conductor (PEC) and Au. The optical constants of Si and Au were taken from Palik and Ghosh and from Johnson and Christy, respectively.
3：List of Experimental Equipment and Materials:
A mesh size of 3 nm was used in the illuminated region, and perfectly matched layers were employed at the boundary to terminate the finite simulation region.
4：Experimental Procedures and Operational Workflow:
The electric field distribution calculated for a focused AP beam at the focal plane was shown. The scattering spectra calculated for the Si NS suspended in air and that placed on a PEC substrate were presented.
5：Data Analysis Methods:
The multipole decompositions performed for the Si NS without and with the PEC substrate were compared. The electric and magnetic field distributions calculated for the two Si NSs at the MD resonances were presented.
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