title: Toroidal lasing spaser.
abstract: Toroidal shapes are often found in bio-molecules, viruses, proteins and fats, but only recently it was proved experimentally that toroidal structures can support exotic high-frequency electromagnetic excitations that are neither electric or magnetic multipoles. Such excitations, known as toroidal moments, could be playing an important role in enhancing inter-molecular interaction and energy transfer due to its higher electromagnetic energy confinement and weaker coupling to free space. Using a model toroidal metamaterial system, we show that coupling optical gain medium with high Q-factor toroidal resonance mode can enhance the single pass amplification to up to 65 dB. This offers an opportunity of creating the "toroidal" lasing spaser, a source of coherent optical radiation that is fueled by toroidal plasmonic oscillations in the nanostructure.
authors: Graduate Institute of Applied Physics, National Taiwan University, Taipei, Taiwan.
authors: Yao-Wei
authors: YW
authors: Huang
authors: Wei Ting
authors: WT
authors: Chen
authors: Pin Chieh
authors: PC
authors: Wu
authors: Vassili A
authors: VA
authors: Fedotov
authors: Nikolay I
authors: NI
authors: Zheludev
authors: Din Ping
authors: DP
authors: Tsai
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