Grating coupling to surface plasma waves. II. Interactions between first-And second-Order coupling

Saleem H. Zaidi, M. Yousaf, S. R J Brueck

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

For grating periods larger than the excitation wavelength, multiple-grating orders couple incident optical radiation to the surface plasma waves (SPW’s) characteristic of the metal-air interface. For a grating period that is an integral multiple of the wave vector of these surface modes, two resonances become degenerate in coupling angle. There are also permitted diffraction orders at this coupling angle. The vicinity of this multiple-mode coupling resonance, where several free-space electromagnetic modes, as well as two surface modes, arecoupled by different orders of a grating, is known as a minigap region. Not surprisingly, the response surface displays complex dependences on frequency, angle, and grating profile. A detailed experimental and theoreticalstudy is presented of the optical response at 633 nm in the (+1, −2) minigap region forAg filmsdeposited on photolithographically defined 870-nm-period gratings. Measurements of both the 0-order reflectance and the −1-order diffraction are presented for a wide progression of grating depths. The SPW resonances depend on the grating depth, and this variation is used to tune throughthe minigap region for a fixed wavelength and period. Similar measurements are presented for a singlegrating as a function of wavelength through the minigap region. In both measurements the 0-order response shows only a single broad minimum as the resonances approach degeneracy, while the −1-order diffraction shows clearly defined momentum gaps. A simple theoretical model based on the Rayleigh hypothesis is presented that gives a good qualitative picture of the response. The response surfaces are sensitive to the grating profile, and detailedmodeling requires inclusion of higher-order grating components.

Original languageEnglish
Pages (from-to)1348-1359
Number of pages12
JournalJournal of the Optical Society of America B: Optical Physics
Volume8
Issue number6
DOIs
Publication statusPublished - 1991
Externally publishedYes

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plasma waves
gratings
interactions
diffraction
wavelengths
profiles
progressions
coupled modes
inclusions
electromagnetism
momentum
reflectance
air
radiation

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Statistical and Nonlinear Physics

Cite this

Grating coupling to surface plasma waves. II. Interactions between first-And second-Order coupling. / Zaidi, Saleem H.; Yousaf, M.; Brueck, S. R J.

In: Journal of the Optical Society of America B: Optical Physics, Vol. 8, No. 6, 1991, p. 1348-1359.

Research output: Contribution to journalArticle

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