Engineering the Outcoupling Pathways in Plasmonic Tunnel Junctions via Photonic Mode Dispersion for Low-Loss...

Area of Science:

• Plasmonics and Nanophotonics
• Materials Science
• Quantum Tunneling

Background:

• Inelastic electron tunneling (IET) in plasmonic tunnel junctions (TJs) enables low-voltage, high-rate optical mode excitation.
• Achieving selective outcoupling of these plasmonic modes is a significant challenge.
• Existing methods using nanoscale antennas or 2D materials involve complex fabrication and limited tunability.

Purpose of the Study:

• To develop a simpler, tunable method for controlling plasmonic mode outcoupling selectivity in TJs.
• To investigate the impact of dielectric environment modification on mode selectivity and efficiency.
• To demonstrate a practical approach for enhancing TJ device performance.

Main Methods:

• Utilizing a multilayer dielectric substrate (SiO2-SiN-glass) with tailored permittivity around TJs.
• Employing theoretical modeling and experimental validation to analyze mode outcoupling.
• Characterizing relative coupling efficiencies and figure-of-merit for plasmonic and photonic-like modes.

Main Results:

• Demonstrated optimized mode selectivity by modifying the dielectric medium.
• Achieved high relative coupling efficiencies: 62.77% for plasmonic modes and 29.07% for photonic-like modes.
• Obtained figures-of-merit up to 180 and 140, balancing outcoupling and propagation length (tens of μm).

Conclusions:

• Modifying the dielectric environment offers a facile yet effective route for LDOS engineering and TJ performance customization.
• The proposed method integrates seamlessly with standard thin-film fabrication processes.
• The developed devices are compatible with silicon nitride photonics platforms, paving the way for integrated photonic devices.