Nonradiative energy transfer of electronic excitation between Tm³⁺ ions in Y₂O₃:Tm laser ceramics

The cross relaxation of Tm3+ ions (H-3(4)-> F-3(4), H-3(6)-> F-3(4)) in Y2O3:Tm laser ceramics was studied. This process significantly affects the creation of an inverse population between the F-3(4) and H-3(6) levels of Tm3+ ions in two-micron lasers when they are pumped to the H-3(4) level by laser diodes with a wavelength of lambda(exc)similar to 800 nm. The efficiency of the cross-relaxation process of Tm3+ ions (H-3(4)-> F-3(4), H-3(6)-> F-3(4)) was equal to 97% for Y2O3:Tm ceramics with the thulium concentration of 3 at.%. It was revealed that the nonradiative transfer of electron excitation energy by Tm3+ ions through cross-relaxation (H-3(4)-> F-3(4), H-3(6)-> F-3(4)) is due to the dipole-dipole mechanism. The interaction microparameter C-DA was determined equal to 9.2.10(-39) cm(6)/s.