Ultrafast dynamics of near-field enhancements at an off-resonance nano-dimer via femtosecond laser excitations

Author： Du GuangQing Yang Qing Chen Feng Bian Hao Wu Yanmin Lu Yu Farooq Umar Hou Xun

E-ISSN： 1286-4854|110|2|27006-27006

ISSN： 0295-5075

Source： EPL (EUROPHYSICS LETTERS), Vol.110, Iss.2, 2015-05, pp. : 27006-27006

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Abstract

Giant electric-field enhancements localized on nano-antennas are important for the optical near-field applications in fields such as super-resolution imaging, near-field optical tweezers, and photothermal therapy. Physically, the field enhancement requires plasmon resonance with respect to structure matching. We report a tunable near-field effect, including localized electric-field enhancement and resistive heating at an off-resonance Au nano-sphere dimer via femtosecond laser irradiation. The near field was strongly modified (up to 81 times) with respect to time evolution at a laser fluence of $0.1\ \text{J/cm}^{2}$ . The results are explained as thermal dynamics manipulation of the Au nano-sphere dimer plasmon resonances. This study provides a new alternative route to tailoring the near-field enhancement for wide applications in nano-antennas.