Study on optical properties and upconversion luminescence of K2YF5:Sm3+ single crystals

K2YF5 single crystals doped with Sm3+ ions (K2YF5:Sm3+) have been synthesized by the hydrothermal method at a temperature of 750 K and pressure of 100 MPa. The absorption and luminescence spectra of the K2YF5:Sm3+ samples have been measured at room temperature. Sm3+ luminescence quenching occurs in K2YF5:Sm3+ single crystals at Sm3+ concentrations higher than 2.0 at%. This phenomenon relates to the energy transfer process through cross-relaxation between Sm3+ ions. Dynamics of the energy transfer process has been analyzed by the Inokuti-Hirayama model and the dipole–quadrupole interaction has been found to be a dominant mechanism in this process. Under excitation by 785 nm laser radiation, K2YF5:Sm3+ single crystals show the upconversion luminescence bands in the visible spectral region as well as some sharp and strong emission lines in the near infrared region. The excited state absorption has been defined to be the main mechanism for upconversion luminescence in K2YF5:Sm3+ crystals.