FEMTOSECOND FREE INDUCTION DECAY BEATS IN ND3+YAG CRYSTAL

Femtosecond free induction decay (FID) beats were observed for the F-4 (3/2) - I-4(9/2) transition of Nd3+ ions doped in Y3Al5O12 (YAG) cryst al at room temperature using a mode-locked Ti3+:Al2O3 laser. This is t he first observation of room-temperature dephasing processes in the ti me domain for rare-earth ion doped materials. The FID beat signal show s a dip structure produced by the interference between the pump pulse and the FID signal, and a quantum beat. The FID signal became large an d comparable to the pump pulse as the crystal length was increased. Th e FID intensity evolution due to the pulse propagation is explained we ll by phenomenological equations.