Photonic Bound-States-in-the-Continuum Observed with an Electron Nanoprobe

Zhaogang Dong; Zackaria Mahfoud; Ramón Paniagua-Domínguez; Hongtao Wang; Antonio I. Fernández-Domínguez; Sergey Gorelik; Son Tung Ha; Febiana Tjiptoharsono; Arseniy I. Kuznetsov; Michel Bosman; Joel K. W. Yang

arXiv · 2105.04220

Photonic Bound-States-in-the-Continuum Observed with an Electron Nanoprobe

Zhaogang Dong·Zackaria Mahfoud·Ramón Paniagua-Domínguez·Hongtao Wang·Antonio I. Fernández-Domínguez·Sergey Gorelik·Son Tung Ha·Febiana Tjiptoharsono·Arseniy I. Kuznetsov·Michel Bosman·Joel K. W. Yang

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Abstract

Bound-states-in-the-continuum (BIC)is a wave-mechanical concept that generates resonances with vanishing spectral linewidths. It has many practical applications in Optics, such as narrow-band filters, mirror-less lasing, and nonlinear harmonic generation. As true BIC optical modes non-radiative and confined to the near field of nanostructures, they cannot be excited using propagating light. As a result, their direct experimental observation has been elusive. Rather than using light, we demonstrate probing BIC modes on arrays of silicon nanoantennas using a focused beam of electrons in a tranmission electron microscope. By combining cathodoluminescence (CL) and monochromated electron energy-loss spectroscopy (EELS) with controlled nanofabrication, we provide direct experimental evidence of "true" BIC modes, and demonstrate a BIC mode in the visible spectrum at 720 nm. The ability to observe and quantify these guided resonances with a spatial precision more than two orders of magnitude higher than previous far-field measurements allows the probing of individual elements in the nano-antenna arrays. The high-resolution experimental results are supported by numerical simulations as well as multipolar decomposition analysis, allowing us to demonstrate that the coherent interaction length of the quasi-BIC resonance requires at least 6 neighboring antenna elements, achieving over 60 times higher emissivity than for unpatterned silicon.

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Zhaogang Dong, Zackaria Mahfoud, Ramón Paniagua-Domínguez, Hongtao Wang, Antonio I. Fernández-Domínguez, Sergey Gorelik, Son Tung Ha, Febiana Tjiptoharsono, Arseniy I. Kuznetsov, Michel Bosman, Joel K. W. Yang. 2021-05-10. Photonic Bound-States-in-the-Continuum Observed with an Electron Nanoprobe. https://arxiv.org/abs/2105.04220

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