Near-Field Plasmonic Probe with Super Resolution and High Throughput and Signal-to-Noise Ratio

• Published in: Nano letters Vol. 18; no. 2; pp. 881 - 885
• Main Authors: Jiang, Ruei-Han, Chen, Chi, Lin, Ding-Zheng, Chou, He-Chun, Chu, Jen-You, Yen, Ta-Jen
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 14.02.2018
• Subjects: Fabry−Pérot resonance; signal-to-noise ratio (SNR); surface plasmon polariton (SPP); Near-field scanning optical microscopy (NSOM); super resolution; throughput; plasmonic tip (p-tip); Fabry−Pérot resonance
• DOI: 10.1021/acs.nanolett.7b04142
• ISSN: 1530-6984; 1530-6992

Near-field scanning optical microscopy (NSOM) enables observation of light-matter interaction with a spatial resolution far below the diffraction limit without the need for a vacuum environment. However, modern NSOM techniques remain subject to a few fundamental restrictions. For example, concerning the aperture tip (a-tip), the throughput is extremely low, and the lateral resolution is poor; both are limited by the aperture size. Meanwhile, with regard to the scattering tip (s-tip), the signal-to-noise ratio (SNR) appears to be almost zero; consequently, one cannot directly use the measured data. In this work, we present a plasmonic tip (p-tip) developed by tailoring subwavelength annuli so as to couple internal radial illumination to surface plasmon polaritons (SPPs), resulting in an ultrastrong, superfocused spot. Our p-tip supports both a radial symmetric SPP excitation and a Fabry–Pérot resonance, and experimental results indicate an optical resolution of 10 nm, a topographic resolution of 10 nm, a throughput of 3.28%, and an outstanding SNR of up to 18.2 (nearly free of background). The demonstrated p-tip outperforms state-of-the-art NSOM tips and can be readily employed in near-field optics, nanolithography, tip-enhanced Raman spectroscopy, and other applications.