6533b823fe1ef96bd127f4b3

RESEARCH PRODUCT

Local excitation of surface plasmon polaritons at discontinuities of a metal film: Theoretical analysis and optical near-field measurements

subject

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Nonresonant excitation of surface plasmon polaritons at discontinuities of a gold film is numerically studied and experimentally observed with scanning near-field optical microscopy. It is shown that surface polaritons can be effectively launched at the edges of a metal film illuminated at an angle of incidence greater than the resonant angle of surface polariton excitation. The electromagnetic near-field distribution over a thin metal film exhibits significantly different features under resonant and nonresonant excitations due to different surface polariton excitation mechanisms. In the latter case the field distribution is determined by the interference of the excitation light and surface polaritons launched on air-metal and glass-metal interfaces. In the former case the interference of surface polariton modes excited on different interfaces of a metal film is dominating. The modulation depths of the respective interference patterns correspond to the efficiency of the intensity conversion of the excitation light at the metal discontinuities into surface polaritons of the order of 0.1-0.01 depending on an angle of incidence.