Absorption and luminescence of tetrahedral Co2+ ion in MgAl2O4

Abstract Optical absorption, luminescence, saturation of absorption and lifetime measurements have been carried out on Co-doped MgAl 2 O 4 . The crystal field parameter Dq of 400 cm -1 and the Racah parameters B of 730 cm -1 and C of 3500 cm -1 are estimated for the tetrahedral Co 2+ 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 4 T 1 ( 4 P) level to the lower levels 4 A 2 ( 4 F), 4 T 2 ( 4 F), and 4 T 1 ( 4 F), respectively. Strong luminescence quenching due to nonradiative decay processes is observed. Saturation of Co 2+ absorption at 540 nm is measured and the absorption cross section is estimated to be (2.1 ± 0.2) × 10 -19 cm 2 .