| Popis: |
Optical fibers have proven to be one of the most important nonlinear media, even though in most cases the nonlinearity exploited is the notoriously weak Kerr effect of the silica-based fiber. By using doped fibers, new, stronger nonlinearities are possible. These stronger effects could allow for new phenomena and applications. Coherent effects, in particular, should be important when pulses shorter or comparable to the dephasing time of the impurity ions propagate in the fiber. Here we report, for the first time, the observation of accumulated photon-echo and free induction decay during the propagation of femtosecond pulses in Er doped fibers at 4.2°K. |
