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Proceedings Paper

Spatial coherence of the thermal electromagnetic field in the vicinity of a dielectric slab
Author(s): Wah Tung Lau; Jung-Tsung Shen; Georgios Veronis; Shanhui Fan
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Paper Abstract

We analyze the spatial coherence of thermal field emitted from a lossy dielectric slab using fluctuation-dissipation theorem.1 For a given wavelength λ, the coherence property varies drastically with the distance from the slab surface. The coherence length is roughly λ / 2 in the far-field zone, but in the extreme near-field zone, it is many orders of magnitude smaller than λ, due to spatially fluctuating surface charges at the air-dielectric interface. On the other hand, in the intermediate near-field zone, the coherence length can be much longer than λ / 2 if the loss is small, because of the presence of waveguide modes of the slab. Such long-ranged coherence falls off approximately as 1/√x , in contrast to 1/x for a blackbody radiator, where x refers to displacement parallel to the slab surface. Furthermore, at a point of fixed distance from the slab surface, the frequency spectrum of the local energy density exhibits distinct fluctuation pattern, which is shown to be closely related to the waveguide dispersion relation.

Paper Details

Date Published: 11 February 2008
PDF: 12 pages
Proc. SPIE 6901, Photonic Crystal Materials and Devices VII, 690109 (11 February 2008); doi: 10.1117/12.761909
Show Author Affiliations
Wah Tung Lau, Stanford Univ. (United States)
Jung-Tsung Shen, Stanford Univ. (United States)
Georgios Veronis, Stanford Univ. (United States)
Shanhui Fan, Stanford Univ. (United States)


Published in SPIE Proceedings Vol. 6901:
Photonic Crystal Materials and Devices VII
Ali Adibi; Shawn-Yu Lin; Axel Scherer, Editor(s)

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