Thermally excited near-field radiation and far-field interference

Thermal radiation from samples of Au layers patterned on GaAs, SiO(2), and SiC at 300 K are studied with a scattering-type scanning near-field optical microscope (wavelength: ~14.5 μm), without applying external illumination. Clear near-field images are obtained with a spatial resolution of ~60 nm....

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Bibliographic Details
Published in:Optics express 2011-04, Vol.19 (8), p.7695-7704
Main Authors: Kajihara, Yusuke, Kosaka, Keishi, Komiyama, Susumu
Format: Article
Language:English
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Summary:Thermal radiation from samples of Au layers patterned on GaAs, SiO(2), and SiC at 300 K are studied with a scattering-type scanning near-field optical microscope (wavelength: ~14.5 μm), without applying external illumination. Clear near-field images are obtained with a spatial resolution of ~60 nm. All the near field signals derived from different demodulation procedures decrease rapidly with increasing probe height h with characteristic decay lengths of 40 ~60 nm. Near-field images are free from any signature of in-plane spatial interference. The findings are accounted for by theoretically expected surface evanescent waves, which are thermally excited in the close vicinity of material surfaces. Outside the near-field zone (1 μm < h), signals reappear and vary as a sinusoidal function of h, exhibiting a standing wave-like interference pattern. These far-field signals are ascribed to the effect of weak ambient radiation.
ISSN:1094-4087
1094-4087
DOI:10.1364/oe.19.007695