Affiliation:
1. School of Computer and Electronic Information Nanjing Normal University Nanjing Jiangsu 210023 China
2. College of Renewable Energy Hohai University Changzhou Jiangsu 213000 China
Abstract
AbstractThere is an increasing demand for label‐free imaging of subwavelength low‐index dielectric samples with high contrast and high sensitivity using a dark‐field optical microscope. However, subwavelength low‐index dielectric samples usually do not show strong Mie scattering resonance characteristics due to the weak light confining ability, which makes them difficult to clearly resolve under a traditional optical microscope. In this work, a fast, simple, and effective approach is proposed to enhance the optical response of subwavelength low‐index dielectric samples by using metallic substrate‐enhanced scattering nanoscopy. It is found that the high reflectance of a substrate can significantly enhance the electric dipole resonance of a SiO2 nanoparticle and the substrate‐nanoparticle interaction, which amplifies the scattering signal of the sample and improves the imaging contrast. Compared with the silica substrate, the Ag‐coated substrate can enhance the scattering intensity of a SiO2 nanoparticle up to 3.7 times under 540 nm wavelength illumination. Furthermore, label‐free stand‐alone 50‐nm‐radius SiO2 nanoparticles and ≈100‐nm‐thick bacterial capsules can be clearly observed when placed on Ag‐coated substrates under a conventional dark‐field optical microscope. The substrate‐enhanced subwavelength‐resolution scattering nanoscopy can enhance the scattering of low‐index subwavelength samples and benefit a significant application in biology, medical testing, and optical detection.
Funder
Fundamental Research Funds for the Central Universities
National Natural Science Foundation of China
Subject
Atomic and Molecular Physics, and Optics,Electronic, Optical and Magnetic Materials