TMDC-Based Topological Nanospaser: Single and Double Threshold Behavior

Abstract

We theoretically study a topological nanospaser, which consists of a silver nanospheroid and MoS 2 monolayer flake of a circular shape. The metal nanospheroid acts as a plasmonic nanoresonator that supports two rotating modes, which are coupled to the corresponding valleys of MoS 2 . We apply external circularly polarized light that selectively pumps only one of the valleys of MoS 2 . The generated spaser dynamics strongly depends on the size (radius) of the MoS 2 nanoflake. For a small radius, the system has only one spasing regime when only the chirally matched plasmon mode is generated, while at a larger size of MoS 2 , depending on the pump intensity, there are two regimes. In one regime, only the chirally matched plasmon mode is generated, while in the other regime both chirally matched and chirally mismatched modes exist. Different regimes of spaser operation also have opposite handedness of the far-field radiated spaser system. Such a topological nanospaser has potential applications in different areas of infrared spectroscopy, sensing, probing, and biomedical treatment.

Ultrafast pulse pumping of topological nanospaser

“…These modes are topologically protected, as shown in [26]. If the TMDC nanoflake has a radius that is larger than the radius of the nanospheroid, then there are two spasing regimes [27]. In one regime, only one spasing mode is generated, while in another regime, two spasing modes coexist.…”

“…There has been recent focus on a new sub-field of spasers, topological spasers [26][27][28]. A spacer, in general, consists of two main elements: (i) a gain medium and (ii) a plasmonic system.…”

“…If the plasmonic system has a topological nature, for example, the plasmonic system consists of an array of metal nanoshells with a honeycomb structure [28], then the corresponding spaser is called the type I topological spaser. But if the gain medium has a nontrivial topology, such as a nanopatch of gapped graphene, then such a spaser is a type II topological spaser [26,27]. In the present paper, we examine the properties of type II topological spaser.…”

“…In one regime, only one spasing mode is generated, while in another regime, two spasing modes coexist. Which regime is realized depends on the strength of the gain [27].…”

Three-level Spaser System: a Semi-Classical Analysis

“…[36,37]. Recently, the topological spasers of type I and II were introduced [38][39][40], where the spaser dynamics is protected by nontrivial topological properties of either a plasmonic system [38] or a gain medium [39,40].…”