Approaching the Purcell factor limit with whispering-gallery hyperbolic phonon polaritons in hBN nanotubes

Xiangdong Guo; Ning Li; Xiaoxia Yang; Ruishi Qi; Chenchen Wu; Ruochen Shi; Yuehui Li; Yang Huang; F. Javier García de Abajo; En-Ge Wang; Peng Gao; Qing Dai

arXiv · 2112.11820

Approaching the Purcell factor limit with whispering-gallery hyperbolic phonon polaritons in hBN nanotubes

Xiangdong Guo·Ning Li·Xiaoxia Yang·Ruishi Qi·Chenchen Wu·Ruochen Shi·Yuehui Li·Yang Huang·F. Javier García de Abajo·En-Ge Wang·Peng Gao·Qing Dai

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Abstract

Enhanced light-matter interaction at the nanoscale is pivotal in the foundation of nonlinear optics, quantum optics, and nanophotonics, which are essential for a vast range of applications including single-photon sources, nanolasers, and nanosensors. In this context, the combination of strongly confined polaritons and low-loss nanocavities provides a promising way to enhance light-matter interaction, thus giving rise to a high density of optical states, as quantified by the so-called Purcell factor - the ratio of the decay rate of an optical quantum emitter to its value in free space. Here, we exploit whispering-gallery hyperbolic-phonon-polariton (WG-HPhP) modes in hBN nanotubes (BNNTs) to demonstrate record-high Purcell factors (~10^12) driven by the deep-subwavelength confinement of phonon polaritons and the low intrinsic losses in these atomically smooth nanocavities. Furthermore, the measured Purcell factor increases with decreasing BNNT radius down to 5 nm, a result that extrapolates to ~10^14 in a single-walled BNNT. Our study supports WG-HPhP modes in one-dimensional nanotubes as a powerful platform for investigating ultrastrong light-matter interactions, which open exciting perspectives for applications in single-molecular sensors and nanolasers.

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Xiangdong Guo, Ning Li, Xiaoxia Yang, Ruishi Qi, Chenchen Wu, Ruochen Shi, Yuehui Li, Yang Huang, F. Javier García de Abajo, En-Ge Wang, Peng Gao, Qing Dai. 2021-12-22. Approaching the Purcell factor limit with whispering-gallery hyperbolic phonon polaritons in hBN nanotubes. https://arxiv.org/abs/2112.11820

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