Reversible upconversion switching for Ho/Yb codoped (K,Na)NbO3 ceramics with excellent luminescence readout capability

Luminescent readout capability for photochromic materials plays a critical role in 3D optical data storage applications, especially for inorganic photochromic materials in the solid-state form. In our previous studies, we found that the luminescent readout capability can be improved using two or multiple-photon excited luminescent mode (upconversion), which can effectively decrease the destruction degree of the excitation energies to the stored information during the luminescent reading process. However, the luminescent readout performance is unsatisfactory owing to the absence of nondestructive luminescence readout capability. Herein, we report a new solid-state photochromic material with excellent upconversion readout capability: Ho3+/Yb3+ codoped (K,Na)NbO3. Upon 407 nm light irradiation, the luminescent switching contrast (Delta R-t) is up to 78%. Particularly, the materials almost have no any re-absorption to 980 nm light, exhibiting extremely low destruction to information recording points. The luminescent readout intensity retains 96% after constant 980 nm irradiation for 4 minutes at a high pumping power of 1W, which is superior to our previously reported results (Er/Yb codoped Bi2.5Na0.5Nb2O9 materials). This work would help to further develop new inorganic photochromic materials with high performance to satisfy the requirements for optical storage devices.