Abstract:The enhanced electric field at plasmonic resonances in nanoscale antennas can
lead to efficient harmonic generation, especially when the plasmonic geometry is
asymmetric on either inter-particle or intra-particle levels. The planar
Archimedean nanospiral offers a unique geometrical asymmetry for second-harmonic
generation (SHG) because the SHG results neither from arranging centrosymmetric
nanoparticles in asymmetric groupings, nor from non-centrosymmetric
nanoparticles that retain a local axis of symmetry. Here, we report forward SHG
from planar arrays of Archimedean nanospirals using 15 fs pulses from a
Ti:sapphire oscillator tuned to 800 nm wavelength. The measured
harmonic-generation efficiencies are 2.6·10−9, 8·10−9 and
1.3·10−8 for left-handed circular, linear, and right-handed
circular polarizations, respectively. The uncoated nanospirals are stable under
average power loading of as much as 300 μWper nanoparticle. The nanospirals also
exhibit selective conversion between polarization states. These experiments show
that the intrinsic asymmetry of the nanospirals results in a highly efficient,
two-dimensional harmonic generator that can be incorporated into metasurface
optics.
Efficient forward second-harmonic generation from planar archimedean nanospirals
