W-band Aperture-Type Scanning Near-Field Microscopy Using Tapered Plastic Probe
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An aluminum-coated PMMA tapered probe with 50 μm aperture was employed in near-field imaging at 110 GHz. The probe was chosen for near-field imaging experiments according to finite-difference time-domain electromagnetic simulation, analysis of antenna resonance, and impedance matching consideration. Imaging of a printed circuit board with a repeated structure of 450-μm-wide metal strips spaced by 550-μm-wide dielectric demonstrated a spatial resolution of 15 μm (λ/200), which is not just 100 times below the diffraction limit, but is 3 times smaller than the aperture size. Subsurface buried defect in a plastic plate (polytetrafluoroethylene defect in polyester fiber glass, 0.5 mm below the top surface of the plate) was also imaged, with a spatial resolution of 1.5 mm, and positioning error of the defect less than 0.5 mm.
KeywordsW-band Near-field imaging Aperture-type scanning probe Plastic probe
Dr. Wei Fan participated in the early stages of this work and Mr. Yanbo Zhang performed the programming for the experiment, and their contributions are gratefully acknowledged.
We gratefully acknowledge financial support of this work from the National Natural Science Foundation of China (61705120), the Ministry of Science and Technology of China (2015CB755401), and the Department of Science and Technology of Shandong Province (2017GGX10108, 2018GGX101043).
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