Abstract
Individual nanometer-sized plasmonic antennas are excited resonantly with few-cycle laser pulses in the near infrared. Intense third-harmonic emission of visible light prevails for fundamental photon energies below 1.1 eV. Interband luminescence and second harmonic generation occur solely at higher driving frequencies. We attribute these findings to multiphoton resonances with the d-band transitions of gold. The strong third-order signal allows direct measurement of a subcycle plasmon dephasing time of 2 fs, highlighting the efficient radiation coupling and broadband response of the devices.
Highlights
Individual nanometer-sized plasmonic antennas are excited resonantly with few-cycle laser pulses in the near infrared
Experiments were performed by exciting nanoantennae with ultrashort laser pulses originating from Ti:sapphire lasers operating at photon energies around 1.5 eV
To single out individual nanoantennae, we focus to a spot diameter of 2 m via all-reflective optics, minimizing dispersion and achromatism
Summary
Individual nanometer-sized plasmonic antennas are excited resonantly with few-cycle laser pulses in the near infrared. For structures with feed gaps wider than g 1⁄4 40 nm, high emission intensities are observed when the excitation bandwidth includes wavelengths corresponding to a quarter of a single antenna arm, i.e., for l % 300 nm [6,7].
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