Photon avalanche (PA)—where the absorption of a single photon initiates a ‘chain reaction’ of additional absorption and energy transfer events within a material—is a highly nonlinear optical process that results in upconverted light emission with an exceptionally steep dependence on the illumination intensity. Over 40 years following the first demonstration of photon avalanche emission in lanthanide-doped bulk crystals, PA emission has been achieved in nanometer-scale colloidal particles. The scaling of PA to nanomaterials has resulted in significant and rapid advances, such as luminescence imaging beyond the diffraction limit of light, optical thermometry and force sensing with (sub)micron spatial resolution, and all-optical data storage and processing. In this review, we discuss the fundamental principles underpinning PA and survey the studies leading to the development of nanoscale PA. Finally, we offer a perspective on how this knowledge can be used for the development of next-generation PA nanomaterials optimized for a broad range of applications, including mid-IR imaging, luminescence thermometry, (bio)sensing, optical data processing and nanophotonics.

中文翻译：

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无机镧系元素掺杂纳米材料的光子雪崩发光研究进展


光子雪崩 （PA） 是指单个光子的吸收引发材料内额外吸收和能量传递事件的“链式反应”，是一种高度非线性的光学过程，会导致上转换光发射，对照明强度的依赖性非常大。在镧系元素掺杂的体晶体中首次证明光子雪崩发射 40 多年后，PA 发射已在纳米级胶体颗粒中实现。PA 扩展到纳米材料带来了重大而快速的进步，例如超越光衍射极限的发光成像、具有（亚）微米空间分辨率的光学测温和力传感，以及全光学数据存储和处理。在这篇综述中，我们讨论了支撑 PA 的基本原理，并调查了导致纳米级 PA 发展的研究。最后，我们提出了如何将这些知识用于开发针对广泛应用优化的下一代 PA 纳米材料的观点，包括中红外成像、发光测温、（生物）传感、光学数据处理和纳米光子学。