Cr3+ luminescence quenching in stoichiometric lithium niobate crystals

Cr3+-doped stoichiometric LiNbO3 crystals were grown and detailed spectroscopic investigations were performed. The samples are characterized by extremely low frequency factor of the luminescence thermal quenching. Its numerical value 1.7 × 108 s−1 is about 104 times lower than in crystals of lithium-aluminum fluorides. Under such conditions, radiative transitions of Cr3+ ions compete successfully with non-radiative ones, resulting in a relatively high quantum yield of the broadband luminescence at room temperature. The quenching of luminescence is counteracted by the effect of the dynamic removal of the radiative transition exclusion, and as a result, Cr3+ radiative lifetime in LiNbO3 decreases from 8 to 4 μs when temperature grows up from 77 to 300 K. Therefore quantum yield of the broadband luminescence at room temperature is not 5–10%, as reported previously, but about 30%. The results obtained in the present study show the stoichiometric lithium niobate doped with Cr3+ ions to be a potential active media for tunable lasers.