ABSORPTION AND LUMINESCENCE OF TETRAHEDRAL CO2+ ION IN MGAL2O4

Optical absorption, luminescence, saturation of absorption and lifetim e measurements have been carried out on Co-doped MgAl(2)O4. The crysta l field parameter Dq of 400 cm(-1) and the Racah parameters B of 730 c m(-1) and C of 3500 cm(-1) are estimated for the tetrahedral Co2+ ion. Luminescence bands observed in the visible at 660 nm and in the near infrared at 880 and 1270 nm are assigned to transitions from the T-4(1 )(P-4) level to the lower levels (4)A(2)(F-4),T-4(2)(F-4), and T-4(1)( F-4), respectively. Strong luminescence quenching due to nonradiative decay processes is observed. Saturation of Co2+ absorption itt 540 nm estimated and the absorption cross section is estimated to be (2.1 +/- 0.2) x 10(-19) cm(2).