Study of relaxation dynamics of excited state of GR1 centers in diamond

We study the decay kinetics of excited state of GR1 center in diamond using 633 nm pump pulse and 658 nm CW probe beam. The absorption saturation followed by a strong absorption of the probe below steady-state transmission level was observed. The recovery of the centers to the original level occurs slowly with ~500 ns time scale and reveals multi-exponential rates with no long-term bleaching or residual absorption. The branching ratio for relaxation process to the ground state and to the metastable state was estimated to be ~ 0.50.