From being an unfavorable consequence to finding itself as the intended imaginary part of a non-Hermitian system, loss has truly emerged as more of a friend than a foe in the context of acoustic metasurfaces. With the promising features of sub-wavelength geometries and the rapid advances in manufacturing techniques that can enable their realization, loss becomes a central topic of discussion. Further, the capability of introducing and tailoring loss allows it to serve as a new degree of freedom in passive wavefront shaping devices. In this review, the authors look back at the recent progress in the field of lossy acoustic metasurfaces. The background behind loss in deep sub-wavelength geometries and the instinctive responses to treat them and exploit them are overviewed, followed by more recent works that embrace and tailor their behavior for unconventional applications. The forthcoming years for acoustic metasurfaces thus hold several promising avenues for exploration, with loss as the protagonist.

中文翻译：

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声学超表面的损失：因祸得福

从不利的结果到发现自己是非厄米系统的预期虚构部分，在声学超表面的背景下，损失确实更像是朋友而不是敌人。随着亚波长几何形状的有前途的特征以及可以实现它们的制造技术的快速进步，损耗成为讨论的中心话题。此外，引入和调整损耗的能力使其成为无源波前整形设备的新自由度。在这篇综述中，作者回顾了有损声学超表面领域的最新进展。概述了深亚波长几何损失背后的背景以及处理和利用它们的本能反应，其次是最近的工作，这些工作包含并为非常规应用定制了他们的行为。因此，声学超表面的未来几年将有几个有希望的探索途径，损失是主角。