Deep subwavelength confinement and threshold engineering in a coupled nanorods based spaser.

Area of Science:

• Photonics and Nanotechnology
• Plasmonics
• Semiconductor Nanostructures

Background:

• Extensive research focuses on developing low-threshold spasers and plasmonic nanolasers at the deep subwavelength scale.
• Coupled-nanorod structures offer potential for energy concentration and amplification in nanoscale volumes.

Purpose of the Study:

• To design and analyze plasmonic nanolaser structures using metallic and cadmium sulfide (CdS) coupled nanorods.
• To investigate how varying nanorod cross-sectional shapes (regular polygons) impacts nanolaser characteristics.

Main Methods:

• Utilized the finite element method (FEM) for numerical simulations.
• Designed and analyzed various coupled nanorod configurations with different metallic cores and semiconductor gain materials (CdS, ZnO).
• Investigated the effect of geometric parameters, specifically the use of regular polygons for cross-sections.

Main Results:

• Achieved a normalized mode area as low as 0.0062 with hexagonal metallic cores and circular semiconductor nanorods.
• Demonstrated a low threshold gain of 1.310 μm⁻¹ using circular silver (Ag) cores with hexagonal CdS nanorods.
• Observed a tenfold reduction in normalized mode area using dodecagonal metallic cores and circular zinc oxide (ZnO) nanorods.

Conclusions:

• Geometric engineering of coupled nanorod structures is crucial for optimizing plasmonic nanolaser performance.
• Regular polygonal cross-sections offer a pathway to significantly enhance light confinement and reduce lasing thresholds.
• The use of ZnO as a gain material shows promise for achieving superior mode confinement in plasmonic nanolasers.