Open AccessThermally excited near-field radiation and far-field interference
Author(s) -
Yusuke Kajihara,
Keishi Kosaka,
S. Komiyama
Publication year - 2011
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.19.007695
Subject(s) - optics , near and far field , interference (communication) , wavelength , materials science , scattering , excited state , radiation , interference microscopy , field (mathematics) , near field scanning optical microscope , microscope , physics , optical microscope , atomic physics , scanning electron microscope , channel (broadcasting) , electrical engineering , mathematics , pure mathematics , engineering
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.