Optimization of the Field Enhancement and Spectral Bandwidth of Single and Coupled Bimetal Core–Shell Nanoparticles for Few-Cycle Laser Applications
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We have theoretically studied and optimized the field enhancement and temporal response of single and coupled bimetal Ag/Au core–shell nanoparticles (NPs) with a diameter of 160 nm and compared the results to pure Ag and Au NPs. Very high-field enhancements with an amplitude reaching 100 (with respect to the laser field centered at 800 nm) are found at the center of a 2-nm gap between Ag/Au core–shell dimers. We have explored the excitation of the bimetal core–shell particles by Fourier transform-limited few-cycle optical pulses and identified conditions for an ultrafast plasmonic decay on the order of the excitation pulse duration. The high-field enhancement and ultrafast decay makes bimetal core–shell particles interesting candidates for applications such as the generation of ultrashort extreme ultraviolet radiation pulses via nanoplasmonic field enhancement. Moreover, in first experimental studies, we synthesized small bimetal Ag/Au core–shell NPs and compared their optical response with pure Au and Ag NPs and numerical results.
KeywordsPlasmonic absorption spectra Nanoplasmonic field enhancement Few-cycle laser pulses Nanoparticle synthesis Core–shell nanoparticles
This work was supported by the BMBF under PhoNa, contract number 03IS2101B, the DFG via the Emmy-Noether program and SPP1391. M.F.K. acknowledges support from KAIN within the KSU-MPQ collaboration, and S.L.S. acknowledges a fellowship from the Alexander von Humboldt Foundation.
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