Visualizing the bidirectional optical transfer function for near-field enhancement in waveguide coupled plasmonic...

Area of Science:

• Nanophotonics
• Metrology
• Plasmonics

Background:

• Plasmonic devices enable nanoscale optical excitation and readout, overcoming diffraction limits.
• Near-field devices are essential for advanced applications but require precise metrology for development.

Purpose of the Study:

• To report visualizations of the bidirectional near-field optical transfer function for waveguide-coupled plasmonic transducers.
• To establish a metrology technique vital for the mass fabrication of near-field devices.

Main Methods:

• Acquired visualizations via scanning electron microscopy (SEM) with cathodoluminescence and scattering scanning near-field optical microscopy (s-SNOM).
• Used SEM as a probe for near-field excitation and cathodoluminescence, collecting far-field light from the waveguide's back facet.
• Employed s-SNOM to map optical near-field mode density with far-field light focused into the waveguide's back facet.

Main Results:

• Demonstrated strong agreement between SEM, s-SNOM measurements, and numerical modeling.
• Validated the visualization technique for characterizing plasmonic transducer modes.

Conclusions:

• The developed metrology enables crucial comparisons between fabricated device performance and theoretical models.
• This technique is extendable to the successful development of future near-field-on-chip devices, including optical processor interconnects.