Topological Nanospaser

TL;DR

This paper introduces a topological nanospaser combining a plasmonic nanodisk and a chiral 2D gain medium, enabling selective generation of chiral light with potential applications in nanooptics and biomedical imaging.

Contribution

It presents a novel topological nanospaser design using a TMDC monolayer and plasmonic nanodisk, demonstrating topological protection of chiral modes.

Findings

Achieves selective chiral mode generation via valley-selective pumping.

Topological protection suppresses time-reversed modes.

Potential for chiral nanolabels and biomedical applications.

Abstract

We propose a nanospaser made of an achiral plasmonic-metal nanodisk and a two-dimensional chiral gain medium -- a monolayer transition-metal dichalcogenide (TMDC). When one valley of the TMDC is selectively pumped (e.g., by a circular-polarized radiation), the spaser generates a mode carrying a topological charge (chirality) that matches that of the gain valley. The chirally mismatched, time-reversed mode has exactly the same frequency but the opposite topological charge; it is actively suppressed by the gain saturation (population clamping) and never generates leading to a strong topological protection for the generating matched mode. This topological spaser is promising for the use in nanooptics and nanospectroscopy in the near-field especially in applications to biomolecules that are typically chiral. Another potential application is a chiral nanolabel for biomedical applications emitting in the far field an intense circularly-polarized coherent radiation.