Highly efficient nanofocusing for integrated on-chip nanophotonics
250-word text abstract
The development of techniques for confining photons efficiently on the deep subwavelength spatial scale will revolutionize scientific research and engineering practices.
The efficient coupling of light into extremely small nanoscale spaces has posed a major
challenge in on-chip nanophotonics due to the need to overcome various loss mechanisms
and the on-chip nanofabrication challenges. Here, we present the experimentally
demonstrated achievement of highly efficient nanofocusing in an Au-SiO2-Au gap
plasmon waveguide using a carefully engineered 3D taper. The dimensions of the SiO2
layer, perpendicular to the direction of wave propagation, tapered linearly below 100 nm.
In simulation, the 3D linear-tapering approach could focus 830 nm light into a 2-by-5
nm2 area with ≤3 dB loss and an intensity enhancement of 3.0 × 104. In a two-photon
luminescence measurement, the device achieved an intensity enhancement of 400 within
a 14-by-80 nm2 area and transmittance of 74%.
Taking a step further, we propose an integration of the 3D linearly tapered gap plasmon
waveguide and impedance-tuning plasmonic crystals to achieve even more efficient
nanoscale on-chip light confinement and manipulation. The proposed nanoplasmonic
structure could achieve an unprecedented maximum intensity enhancement of ~104
within a 103-nm3 volume, with coupling efficiency exceeding 70%. Because of its
noticeably high degree of light confinement and throughput, the integrated device could
potentially be used to implement nanoscale on-chip terahertz light sources and detectors
for next-generation computing and communication applications.
100-word text summary
The efficient on-chip focusing of light into extreme nanoscale spaces requires
engineering solutions to overcome various loss mechanisms and nanofabrication
challenges. Here, we present the experimental demonstration of highly efficient
nanofocusing in an Au-SiO2-Au gap plasmon waveguide using a carefully engineered 3D
taper with 74% transmittance into a 14-by-80-nm2 area; and also propose to integrate the
3D gap plasmon waveguide with impedance-tuning plasmonic crystals to further improve
the on-chip light confinement: intensity enhancement of ~104 within a 103-nm3 volume,
with >70% transmittance. The integrated approach could lead to on-chip, nanoscale
terahertz light sources and detectors for computing and communication applications.