Rare earth solids are important materials widely used in optoelectronics. The notable examples are Nd:YAG as laser materials and Er doped fiber as optical amplifier for optical communication. The ultrafast properties of rare earth materials have not been extensively studied before. However

due to the present development of information technology characterized with broadband signals and tera bit rate data transmission

it is very important to understand the interaction between the rare earth ion and its solid environment

and their corrected role in the coherent dynamic processes. In trivalent rare earth solids

the optically active center involves intra-4f electron transitions. The 4f electrons are well shielded from the crystalline environment by their outer 5s5p electrons. The resulting sharp absorption or emission spectra indicate long surviving optical coherence among various 4f electronic states even at room temperature. We report both time domain and frequency domain linear spectroscopies in the study of coherent dynamic in rare earth powder Eu

3+

:Y

2

O

3

at room temperature. The time domain free induction decay was obtained via an interferometric fluorescence measurement with a pair of phase corrected femtosecond pulses

while the frequency domain signal is via steady state fluorescence excitation. The recorded interferogram exhibits beatings in picosecond time scale arising from the interferences among various weakly split of 4f electronic states. The separation of the involved energy levels deduced from the beating is approximately 1.1 nm

in agreement with that obtained from the excitation spectra. Analysis with the theory of multi level excitation resulted quantum interference shows that the experimental results can be well explained. Rare earth is often used as gain medium of laser

one gain curve include many stark split electronic levels. The long coherent relaxation time indicates its possible to enhance the population of one electronic level while depressing the population of other electronic levels by quantum interference control. The research on quantum interference of rare earth ions shows its potential application in stimulated light amplification.