Coupling matter excitations to electromagnetic modes inside nano-scale optical resonators leads to the formation of hybrid light-matter states, so-called polaritons, allowing the controlled manipulation of material properties. Here, we investigate the photo-induced dynamics of a prototypical strongly-coupled molecular exciton-microcavity system using broadband two-dimensional Fourier transform spectroscopy and unravel the mechanistic details of its ultrafast photo-induced dynamics. We find evidence for a direct energy relaxation pathway from the upper to the lower polariton state that initially bypasses the excitonic manifold of states, which is often assumed to act as an intermediate energy reservoir, under certain experimental conditions. This observation provides new insight into polariton photophysics and could potentially aid the development of applications that rely on controlling the energy relaxation mechanism, such as in solar energy harvesting, manipulating chemical reactivity, the creation of Bose–Einstein condensates and quantum computing.

纳米级光谐振器内部物质与电磁模式的耦合激发导致形成混合光物质状态，即所谓的极化子，从而可控制地控制材料性能。在这里，我们研究使用宽带二维傅立叶变换光谱学的原型强耦合分子激子-微腔系统的光诱导动力学，并揭示其超快光诱导动力学的机理细节。我们发现有证据表明，从上极化子态到下极化子态的直接能量弛豫路径最初绕过了态的激子流形，在某些实验条件下，通常认为它是作为中间能量库。