Tip-enhanced Near-field Optical Microscopy Based on a Plasmonic Lens/ Probe

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Important Dates

Conference:

Aug. 18-20, 2018

Full Paper Due: Jul. 20, 2018

Abstract Due: Jul. 20, 2018

Audience Registration Due:
Aug. 18, 2018

Presentations of The Int'l Symposium on Photonics and Optoelectronics (SOPO 2016)

● Tip-enhanced Near-field Optical Microscopy Based on a Plasmonic Lens/ Probe
Author(s)
Mingqian Zhang
Affiliation(s)
QIan Xuesen Laboratory of space technology
KEYWORDS
Optical Microscopy, Plasmonic Lens/ Probe
ABSTRACT
Tip-enhanced near-field optical microscopy is a promising scanning probe technique for exploring near-field optical properties of individual objects and structures on the nanoscale. It is capable of obtaining corresponding topographical and optical information with resolution beyond the diffraction limit and grants remarkable localized optical signal enhancement. This technique uses a sharp metallic tip regulated in the near-field of a specimen’s surface, which is illuminated with a proper excitation field meeting the excitation conditions of the wave-vector matching. The local optical field interacted with the specimen in the vicinity of the tip apex is effectively enhanced. In this technique, the signal enhancement near the antenna is attributed to the excitation of localized surface plasmons and the lighting-rod effect. Typically, a tip-enhanced near-field optical microscope is composed of a scanning probe microscope, excitation/ collection optical configuration, and a detection device. In this technique, how to optimize the tip-excitation field coupling to improve the detection sensitivity is of crucial importance and receives great research attentions. In this work, two kinds of methods are presented to improve the signal to noise ratio of tip-enhanced near-field optical microscopy by both strengthen the near-field optical signal enhancement and reducing the far-field background noise. First, a tip-enhanced near-field optical microscope based on a plasmonic lens is investigated. A symmetry-breaking strcture plasmonic lens is specifically designed for focusing the surface evanescent wave and generates a longitudinal field dominated excitation field. The focusing property of the longitudinal field by the plasmonic lens is theoretically simulated and experimentally investigated. It is demonstrated that the plasmonic lens is suitable for providing the longitudinal field excitation foe local field enhancement on a tip antenna. Then, the plasmonic lens is utilized in the excitation configuration of the tip-enhanced near-field optical microscope to replace a conventional objective lens. Second, a plasmonic probe which consisted of a taper cylinder tip and a couple of curved nanoslits on the probe base was designed. It is suitable to be used in top-illumination mode tip-enhanced near-field optical microscope to isolate the focused near-field excitation at the probe apex from the contribution of the far-field illumination. The field enhancement and the confinement performance of the probe were investigated using three-dimensional finite-difference time-domain method. The structure of the probe was optimized and fabricated with FIB method. The field enhancement performance of the plasmonic probe was theoretically simulated and experimentally detected.