Optical nanoantennas can convert propagating light to local fields.The local-field responses can be engineered to exhibit nontrivial features in spatial,spectral and temporal domains,where local-field interferences pl...Optical nanoantennas can convert propagating light to local fields.The local-field responses can be engineered to exhibit nontrivial features in spatial,spectral and temporal domains,where local-field interferences play a key role.Here,we design nearly fully controllable local-field interferences in the nanogap of a nanoantenna,and experimentally demonstrate that in the nanogap,the spectral dispersion of the local-field response can exhibit tuneable Fano lineshapes with nearly vanishing Fano dips.A single quantum dot is precisely positioned in the nanogap to probe the spectral dispersions of the local-field responses.By controlling the excitation polarization,the asymmetry parameter q of the probed Fano lineshapes can be tuned from negative to positive values,and correspondingly,the Fano dips can be tuned across a broad spectral range.Notably,at the Fano dips,the local-field intensity is strongly suppressed by up to ~50-fold,implying that the hot spot in the nanogap can be turned into a cold spot.The results may inspire diverse designs of local-field responses with novel spatial distributions,spectral dispersions and temporal dynamics,and expand the available toolbox for nanoscopy,spectroscopy,nano-optical quantum control and nanolithography.展开更多
基金supported by the National Key Research and Development Program of China(2017YFA0205700)the National Natural Science Foundation of China(11621101,61774131,91833303)+2 种基金the Fundamental Research Funds for the Central Universities(2017FZA5001,2018FZA5001)the China Postdoctoral Science Foundation(2017M621920,2017M622722)the Science and Technology Department of Zhejiang Province and the Guangdong Innovative Research Team Program(201001D0104799318).
文摘Optical nanoantennas can convert propagating light to local fields.The local-field responses can be engineered to exhibit nontrivial features in spatial,spectral and temporal domains,where local-field interferences play a key role.Here,we design nearly fully controllable local-field interferences in the nanogap of a nanoantenna,and experimentally demonstrate that in the nanogap,the spectral dispersion of the local-field response can exhibit tuneable Fano lineshapes with nearly vanishing Fano dips.A single quantum dot is precisely positioned in the nanogap to probe the spectral dispersions of the local-field responses.By controlling the excitation polarization,the asymmetry parameter q of the probed Fano lineshapes can be tuned from negative to positive values,and correspondingly,the Fano dips can be tuned across a broad spectral range.Notably,at the Fano dips,the local-field intensity is strongly suppressed by up to ~50-fold,implying that the hot spot in the nanogap can be turned into a cold spot.The results may inspire diverse designs of local-field responses with novel spatial distributions,spectral dispersions and temporal dynamics,and expand the available toolbox for nanoscopy,spectroscopy,nano-optical quantum control and nanolithography.
