Monolayer semiconductor nanocavity lasers with ultralow thresholds

Area of Science:

• Nanophotonics and Quantum Optics
• Materials Science and Engineering
• Solid-State Physics

Background:

• Photonic cavities enhance light emitter performance via cavity quantum electrodynamics (Purcell effect).
• Previous ultralow-threshold nanoscale lasers used quantum dots in photonic crystal cavities (PCCs).
• Quantum dot PCC lasers face challenges: random positioning, compositional variations, difficult current injection, and poor electronic compatibility.

Purpose of the Study:

• To develop a new lasing strategy overcoming limitations of quantum dot-based nanoscale lasers.
• To create an ultralow-threshold, continuous-wave (CW) nanolaser with improved practicality and integration potential.
• To demonstrate a scalable and electronically compatible nanolaser architecture for on-chip optical communication.

Main Methods:

• Utilized an atomically thin tungsten diselenide (WSe2) monolayer as the gain medium.
• Introduced the WSe2 monolayer non-destructively and deterministically onto a pre-fabricated photonic crystal cavity (PCC).
• Employed optical pumping to achieve lasing and investigated the surface-gain geometry.

Main Results:

• Achieved a CW nanolaser operating in the visible regime with an optical pumping threshold as low as 27 nanowatts at 130 K.
• The monolayer WSe2 gain medium confines excitons to within 1 nm of the PCC surface, crucial for lasing action.
• Demonstrated the potential for electrically pumped operation via external controls like electrostatic gating and current injection.

Conclusions:

• The WSe2 monolayer on PCC architecture provides a viable alternative to quantum dot lasers, offering improved control and integration.
• The surface-gain geometry enables unprecedented accessibility for tailoring gain properties and external electrical control.
• This scalable scheme is compatible with integrated photonics, paving the way for advanced on-chip optical communication technologies.