Plasmonic structures are widely used in modern biosensor design. various plasmonic resonant cavities could efficiently achieve a high Q-factor, improving the local field intensity to enhance photoluminescence or SERS (Surface-Enhanced Raman Scattering) of small molecules. Also, the combination between virus-like particles and plasmonic structures could significantly influence the scattering spectrum and field, which is utilized as a method for biological particle detection. In this paper, we designed one kind of gold plasmonic cavity with the shape of a split-ring. An edge gap and a bonus center bulge are introduced in the split-ring structure. Our simulation is based on Finite Difference Time Domain (FDTD) method. Polarization Indirect Microscopic Imaging (PIMI) technique is used here to detect far-field mode distribution under the resonant wavelength. The simulation results demonstrate resonant peaks in the visible spectrum at about 600 nm with a Q-factor reaches to 74. Localized hot spots are generated by an edge dipole mode and a cavity hexapole mode at resonant wavelength, which is according to dark points in the PIMI sinδ image. Also, the split-ring cavity shows a sensitivity when combined with biological particles. The scattering distribution is evidently changed as a result of energy exchange between particles and split-ring cavity, indicating a promising possibility for biosensing.
This paper proposes a new portable polarization parametric indirect microscopy imaging without a liquid crystal (LC) retarder. The polarization was modulated by a polarizer automatically rotating when the camera took raw images sequentially. A specific mark tagged the polarization states of each camera’s snapshot in the optical illumination path. A computer vision portable polarization parametric indirect microscopy imagrecognition algorithm was developed to retrieve the unknown polarization states from each raw camera image to ensure that the right polarization modulation states were used in the PIMI processing algorithm. The system’s performance was verified by obtaining PIMI parametric images of human facial skin. The proposed method avoids the error problem caused by the LC modulator and significantly reduces the whole system’s cost.
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