Tandem Photon Avalanches for Various Nanoscale Emitters with Optical Nonlinearity up to 41st‐Order through Interfacial Energy Transfer

Abstract Photon avalanche has received continuous attention owing to its superior nonlinear dynamics and promising advanced applications. However, its impact is limited due to the intrinsic energy levels as well as the harsh requirements for the composites and sizes of doped materials. Here, with a universal mechanism named tandem photon avalanche (TPA), giant optical nonlinear response up to 41st‐order in erbium ions, one of the most important lanthanide emitters, has been achieved on the nanoscale through interfacial energy transfer process. After capturing energy directly from the avalanched energy state 3 H 4 of Tm 3+ (800‐nm emission), erbium ions also exhibit bright green and red PA emissions with intensities comparable to that of Tm 3+ at a low excitation threshold (7.1 kWcm −2 ). Using the same strategy, effective PA looping cycles are successfully activated in Ce 3+ and Ho 3+ . Additionally, Yb 3+ ‐mediated networks are constructed to further propagate PA effects to lowly‐doped Tm 3+ , enabling 475‐nm PA emission. The newly proposed TPA strategy provides a facile route for generating photon avalanche not only from erbium ions but also from various emitters in multilayered core–shell nanoparticles.