EXPERIMENTAL-EVIDENCE FOR STRONG UV TRANSITION CONTRIBUTION IN THE RESONANT NONLINEARITY OF DOPED FIBERS

We report a new theoretical interpretation of the strong resonantly-en hanced third-order nonlinearity observed in fibers doped with Nd3+, Er 3+, or Yb3+. For each fiber, the absolute contributions of the near re sonance (IR-visible) and far from resonance (UV) transitions to the no nlinearity are calculated and compared to experimental values. We show that in all cases, a large fraction of the measured nonlinearity is d ue to strong UV transitions. The consequences of this: observation on the bandwidth, switching power and response time of switches based on this effect are discussed.