Mirror‑Induced Field Compression Drives Tunable Strong Exciton-Plasmon Polaritons in WS₂/h-BN/Au Heterostructures

Area of Science:

• Nanophotonics
• Quantum Technologies
• Materials Science

Background:

• Scalable nanophotonic and quantum technologies require deep-subwavelength confinement and strong coupling at visible frequencies.
• Transition metal dichalcogenides (TMDs) show promise for confinement, but tunable strong coupling often needs complex nanostructures or material modification.
• In metal-coupled systems, distinguishing metallic mirror effects from exciton-plasmon hybridization is challenging.

Purpose of the Study:

• To introduce a van der Waals (vdW)-integrated, chemically non-invasive WS2/h-BN/Au heterostructure for tunable optical confinement.
• To demonstrate deep-subwavelength optical field control using a controllable nanogap.
• To establish a scalable platform for enhanced nonlinear optics and integrated quantum devices.

Main Methods:

• Fabrication of a WS2/h-BN/Au heterostructure with a tunable h-BN spacer.
• Scattering-type near-field microscopy to map propagating interference fringes and measure polariton wavelengths.
• Full-wave simulations and transfer-matrix analysis to differentiate geometric confinement from plasmonic effects.

Main Results:

• Achieved a TM-polariton wavelength collapse to ~172 nm (71% reduction) with a 5 nm h-BN spacer under 633-nm excitation.
• Demonstrated one of the highest degrees of optical confinement for room-temperature TMDC polaritons.
• Successfully separated geometric mirror confinement from plasmon-assisted hybridization through advanced simulations.

Conclusions:

• The WS2/h-BN/Au heterostructure provides a deterministic route to deep-subwavelength field control.
• This platform offers a chemically non-invasive approach to tune image-charge confinement.
• The developed architecture is scalable for advanced nonlinear optical enhancement and integrated quantum applications.