Cavity-Defined van der Waals Plasmonic Nanolasers Enabled by Out-Of-Plane Dipole Coupling

Area of Science:

• Materials Science
• Optics
• Nanotechnology

Background:

• Plasmonic nanolasers offer subwavelength coherent light but face challenges with rigid designs and gain requirements.
• Indium Selenide (InSe) is a layered material with a direct bandgap and out-of-plane emission, suitable for plasmonic applications.

Purpose of the Study:

• To realize a versatile plasmonic nanolaser platform using van der Waals integrated InSe gain media and engineered gold cavities.
• To investigate lasing characteristics and feedback mechanisms in a cavity-defined plasmonic nanolaser architecture.

Main Methods:

• Van der Waals integration of layered InSe gain media with lithographically engineered gold (Au) cavities, separated by hexagonal boron nitride (hBN) spacers.
• Optical pumping of the InSe gain medium and characterization of near-infrared (NIR) lasing properties.
• Spatially resolved spectroscopy and numerical simulations to analyze lasing feedback and mode behavior.

Main Results:

• Achieved efficient coupling between InSe emission dipoles and surface plasmon polariton (SPP) modes.
• Observed clear NIR lasing with a defined threshold, linewidth narrowing, and reduced carrier lifetime.
• Demonstrated a plasmonic lasing regime below the optical-mode cutoff, sustained for thin InSe layers (down to 79 nm).
• Identified cavity-defined SPP modes as the governing feedback mechanism for lasing.
• Showcased deterministic control over lasing behavior by engineering diverse Au cavity geometries.

Conclusions:

• The developed platform establishes a versatile and general architecture for plasmonic nanolasers.
• The van der Waals integration approach overcomes limitations of rigid cavity designs and demanding gain conditions.
• This work paves the way for novel subwavelength coherent light sources with tunable properties.