Plasmon‐Assisted Self‐Encrypted All‐Optical Memory

All‐optical responsive nanomaterials, which can rapidly switch between two stable states, have been regarded as the next‐generation memories due to their potential to realize binary information storage and implement on‐chip, integrated photonic neuromorphic systems. Rare earth oxides are preeminent candidates owing to their extraordinary luminescent stability and narrow optical transitions. However, due to the lack of simple and effective optical switches, it is difficult to realize all‐optical data storage, encoding, and retrieval by pure rare earth‐doped luminescent nanoparticles. Here, a rapid and high‐contrast of 104 luminescent switching of Y2O3:Eu3+ nanoparticle between the enhancement and quenching states is achieved by employing the strong light confinement and ultrafast thermal response of localized surface plasmon resonance. A self‐encrypted all‐optical memory is presented with optical information writing, encryption, reading, and re‐writing, and a high‐sensitivity synaptic response of emitters to frequency and light intensity flux, which can be harnessed to encrypt information flows and promote convenient and high‐security information encryption. Such a convenient and secure plasmonic thermally assisted self‐encrypting luminescent switch paves the way for constructing high‐performance stimuli‐responsive rare earth oxide crystals on demand and expanding their applications in various data encryption, anti‐counterfeiting, and rewritable colouration devices. A self‐encrypted all‐optical memory with ultrahigh switching contrast is realized in Y2O3:Eu3+–Au. All‐optical information revisible writing, reading, encryption, and re‐writting are realized through a simple change of the irradiation light power. This work not only provides insight into the unique thermal response of the plasmon resonance in the composite structure but also offers good candidates for self‐encrypted binary information storage.