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

Highlights: • K2YF5:Sm3+ crystal is grown by hydrothermal method at temperature of 750 K and pressure of 1500 MPa. • Dynamic of energy transfer process is analyzed by Inokuti-Hirayama model. • Upconversion luminescence of K2YF5:Sm3+ is observed under excitation at 785 nm laser. • Exited state absorption is the dominant mechanism for upconversion luminescence of K2YF5:Sm3+. 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.