Optical invisibility, which started in the pages of fiction before becoming an intriguing quest of humankind for over a century, has blossomed into a remarkable scientific journey toward reality over the last two decades. Perfect optical cloaking requires the total scattering of electromagnetic waves around an object at all angles, all polarizations, over a wide frequency range, irrespective of the medium. Such a device is still far-fetched, requiring the transformation of space around a cloaked region such that the phase velocity is faster than other areas to preserve the phase relationships. However, by simplifying the invisibility requirements, pioneering work on spherical transformation cloaks, carpet cloaks, plasmonic cloaks, and mantle cloaks has been realized in narrowband microwave, infrared, and even optical wavelengths. In this Tutorial, we review the theoretical basis for invisibility cloaking, from spherical transformational optics to non-Euclidian cases, and discuss their limitations. Subsequently, we highlight the recent trends in realizing reconfigurable intelligent cloaks to overcome the traditional limitations of wideband operation and parallel efforts in unidirectional cloaking. Because the human eye is insensitive to the phase and polarization of visible light, a class of ray optics cloaking devices has been recently developed by eliminating phase preservation requirements. Notably, we focus on the recent progress achieved on invisibility cloaks that function in natural incoherent light and can be realized using standard optical components. We conclude this Tutorial with a prospective of potential applications and the practicality of optical cloaks in everyday life.

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光学隐形和隐形：从虚构到技术现实

光学隐形开始于小说的篇幅，然后成为一个多世纪以来人类的一项有趣探索，在过去的二十年里已经发展成为通往现实的非凡科学之旅。完美的光学隐形要求电磁波在一个广泛的频率范围内以任何角度、所有极化在物体周围完全散射，而与介质无关。这样的设备仍然是牵强附会，需要对隐身区域周围的空间进行变换，使相速度比其他区域快，以保持相位关系。然而，通过简化隐身要求，在窄带微波、红外甚至光波长范围内实现了球面变换斗篷、地毯斗篷、等离子体斗篷和地幔斗篷的开创性工作。在本教程中，我们回顾了隐形斗篷的理论基础，从球面变换光学到非欧几里得情况，并讨论了它们的局限性。随后，我们强调了实现可重构智能斗篷的最新趋势，以克服宽带操作和单向斗篷并行工作的传统局限性。由于人眼对可见光的相位和偏振不敏感，最近通过消除相位保持要求开发了一类射线光学隐形装置。值得注意的是，我们专注于最近在自然非相干光下起作用并且可以使用标准光学组件实现的隐形斗篷方面取得的进展。我们以潜在应用的前景和光学斗篷在日常生活中的实用性来结束本教程。