期刊
OPTICS EXPRESS
卷 25, 期 22, 页码 26923-26938出版社
OPTICAL SOC AMER
DOI: 10.1364/OE.25.026923
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资金
- NSF Center for Chemical Innovation, Chemistry at the Space-Time Limit (CaSTL) [CHE-1414466]
- Saudi Arabian Cultural Mission (SACM)
We numerically analyze PiFM's lateral and vertical (subsurface) imaging performance in the visible and IR regimes. The lateral spatial resolution and subsurface imaging capabilities are limited by the field spatial confinement near the tip apex, which is directly proportional to the excitation wavelength. In addition, we show that near-field optical force exerted on the tip due to sample molecular resonance is indeed in the detectable range. Moreover, driving sample on (off) resonance reveals high (low) contrast. The strength of the optical forces is assessed for metal (gold), polymers (Polystyrene and Polymethylmethacrylate), and solid (SiC). By increasing tip-coating thickness from 5 nm to 35 nm, the gap-field enhancement decreases to about 40%. In IR, force spectrum over an absorption band is predominantly following the real part of the polarizability, as predicted by dipole-dipole approximation. (C) 2017 Optical Society of America
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