Spatio-spectral decomposition of complex eigenmodes in subwavelength nanostructures through transmission matrix...

Area of Science:

• Plasmonics and Nanophotonics
• Computational Electromagnetics

Background:

• Exploiting multiple near-field optical eigenmodes enhances optical device design and functionality.
• Near-field optical eigenmodes in subwavelength plasmonic nanostructures are spectrally and spatially multiplexed, complicating individual mode extraction.

Purpose of the Study:

• To introduce a novel method for resolving individual near-field optical eigenmodes in subwavelength nanostructures.
• To enable selective excitation and utilization of specific eigenmodes for advanced optical device engineering.

Main Methods:

• Constructing a transmission matrix for each excitation wavelength using near-field distributions from various incident angles.
• Applying singular value decomposition (SVD) to resolve individual eigenmode profiles and energy spectra.
• Utilizing conventional electromagnetic simulations to validate the transmission matrix analysis.

Main Results:

• Successfully resolved individual orthogonal eigenmodes for single- and double-slot nanoantennas (20 nm slot width).
• Demonstrated the ability to selectively excite specific eigenmodes of nanostructures.
• Validated the effectiveness of transmission matrix analysis in overcoming mode superposition challenges.

Conclusions:

• The proposed transmission matrix analysis method effectively resolves superimposed near-field optical eigenmodes in subwavelength nanostructures.
• This technique allows for the selective excitation and application of individual eigenmodes, advancing optical device design and functionality.