Nanostructured materials offer the possibility to tailor light–matter interaction at scales below the wavelength. Metallic nanostructures benefit from the excitation of surface plasmons that permit light concentration at ultrasmall length scales and ultrafast time scales. The local density of states (LDOS) is a central concept that drives basic processes of light–matter interaction such as spontaneous emission, thermal emission and absorption. We introduce theoretically the concept of LDOS, emphasizing the specificities of plasmonics. We connect the LDOS to real observables in nanophotonics, and show how the concept can be generalized to account for spatial coherence. We describe recent methods developed to probe or map the LDOS in complex nanostructures ranging from nanoantennas to disordered metal surfaces, based on dynamic fluorescence measurements or on the detection of thermal radiation.

纳米结构材料提供了在低于波长的范围内调整光-物质相互作用的可能性。金属纳米结构得益于表面等离激元的激发，允许在超小长度尺度和超快时间尺度上进行光聚集。状态局部密度（LDOS）是一个中心概念，它驱动光与物质相互作用的基本过程，例如自发发射，热发射和吸收。我们从理论上介绍了LDOS的概念，强调了等离子体技术的特殊性。我们将LDOS与纳米光子学中的实际可观察​​物联系起来，并展示了如何将该概念推广以解决空间相干性问题。我们描述了为探测LDOS或在复杂的纳米结构（从纳米天线到无序的金属表面）中绘制地图而开发的最新方法，