Unidirectional Spaser in Symmetry-Broken Plasmonic Core-Shell Nanocavity

Xiangeng Meng, Birck Nanotechnology Center, Purdue University; Kyoto University
Urcan Guler, Birck Nanotechnology Center, Purdue University
Alexander V. Kildishev, Birck Nanotechnology Center, Purdue University
Koji Fujita, Kyoto University
Katsuhisa Tanaka, Kyoto University
Vladimir M. Shalaev, Birck Nanotechnology Center, Purdue University

Abstract

The spaser, a quantum amplifier of surface plasmons by stimulated emission of radiation, is recognized as a coherent light source capable of confining optical fields at subwavelength scale. The control over the directionality of spasing has not been addressed so far, especially for a single-particle spasing nanocavity where optical feedback is solely provided by a plasmon resonance. In this work we numerically examine an asymmetric spaser - a resonant system comprising a dielectric core capped by a metal semishell. The proposed spaser emits unidirectionally along the axis of the semishell; this directionality depends neither on the incident polarization nor on the incident angle of the pump. The spasing efficiency of the semishell-capped resonator is one order of magnitude higher than that in the closed core-shell counterpart. Our calculations indicate that symmetry breaking can serve as a route to create unidirectional, highly intense, single-particle, coherent light sources at subwavelength scale.

Discipline(s)

Nanoscience and Nanotechnology