Leaky-Wave Focusing Metasurfaces Based on Bound States in Continuum for 532 nm

Bound states in the continuum (BICs) are unique states of light that facilitate a sharp resonant response in subwavelength optical structures, associated with extremely high values of the resonance quality (Q) factor approaching infinity. Here, we propose a leaky-wave metasurface (LWM) combining with BICs based on Si<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>N<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> platform working for 532 nm which is able to focus at random height with full width at half maximum (FWHM) of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{0.9}\ \boldsymbol{\mu} \mathbf{m}\times \mathbf{1.1}\ \boldsymbol{\mu} \mathbf{m}$</tex> and nearly 99% theoretical efficiency and experimentally focusing spot image at focal plane.