Absorption and luminescence of tetrahedral Co 2+ ion in MgAl 2O 4

Abstract

Optical absorption, luminescence, saturation of absorption and lifetime measurements have been carried out on Co-doped MgAl 2O 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 4T 1( 4P) level to the lower levels 4A 2( 4F), 4T 2( 4F), and 4T 1( 4F), 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.