Giant Optical Nonlinear Response up to 60th‐Order Induced by the Ytterbium Energy Relay Mediated Photon Avalanches.

The exploration of photon avalanching (PA) luminescence in different lanthanide emitters has profound implications in plentiful frontier applications. However, studies for universal mechanisms at the nanoscale to exhibit giant nonlinear responses in various avalanching emitters are limited. Here, record‐breaking nonlinear responses up to 60th‐order in high‐lying emitting levels of various emitters at room temperature are generated by proposing a universal mechanism named energy relay‐mediated photon avalanche (enrePA). By harnessing energy from the avalanching nano‐engine through the energy relay of Yb3+ ions, the brightness of blue emissions from Tm3+ and Ho3+ can be enhanced with giant optical nonlinearity up to 60th and 38th order, respectively. Further incorporating gadolinium‐based systems, more emitters (Tb3+, Eu3+, Dy3+, Nd3+) can be activated with extreme optical nonlinearities up to 48th‐order. By expanding PA into the full‐spectrum range, the enrePA mechanism opens exciting avenues for flexible and high‐efficiency PA modulation in multilayer nanostructures, enabling the applicability of PA in more technologies such as super‐resolution imaging, lithography, and optical detection. [ABSTRACT FROM AUTHOR]