Optical polarization response at gold nanosheet edges probed by scanning near-field optical microscopy
Zhuan-Fang Bi(毕篆芳)1, Mu Yang(杨沐)2, Guang-Yi Shang(商广义)1
1 Department of Applied Physics, Key Laboratory of Mircro-nano Measurement-manipulation and Physics(Ministry of Education), Beihang University, Beijing 100191, China; 2 Beijing Institute of Space Mechanics and Electronics, CAST, Beijing 100191, China
Abstract Optical properties of metallic edge-like structures known as knife-edges are a topic of interest and possess potential applications in enhanced Raman scattering, optical trapping, etc. In this work, we investigate the near-field optical polarization response at the edge of a triangular gold nanosheet, which is synthesized by a wet chemical method. A homemade scanning near-field optical microscope (SNOM) in collection mode is adopted, which is able to accurately locate its probe at the edge during experiments. An uncoated straight fiber probe is used in the SNOM, because it still preserves the property of light polarization though it has the depolarization to some extent. By comparing near-field intensities at the edge and glass substrate, detected in different polarization directions of incident light, the edge-induced depolarization is found, which is supported by the finite differential time domain (FDTD) simulated results. The depolarized phenomenon in the near-field is similar to that in the far-field.
Fund: Project supported by the National Key Basic Research Program of China (Grant No. 2013CB934004) and the Fundamental Research Funds for the Central Universities, China (Grant No. YWF-13-D2-XX-14).
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