Inter Configuration Excited-State Absorption of Nd3+-Doped Fluoride Crystals

The search for tunable blue-UV solid-state lasers has led to the recognition that 4fn-1 5d to 4P transitions of rare earth ions can potentially be useful for these types of laser systems. Such laser actions has been observed with Ce3+ or Nd3+-doped fluoride crystals. Nevertheless, these lasers suffer from solarization mechanisms which has been found to involve two-photon creation of color centers (via the 4fn →4fn-15d → conduction band pathway). One way to overpass this problem is a stepwise multiphoton excitation of 4fn-15d states with photons of low energy.