Laser excited fluorescence and self-absorption in LaF₃:Nd³⁺

Abstract

Fluorescence of LaF₃:Nd³⁺ has been observed at 77^° K and at room temperature in the region 5170-9020 Å using the Ar⁺, 5145 Å laser excitation. The fluorescence at 77^°K consists of lines orginating in the E,D, and R levels of Nd³⁺ as well as in the K and L levels which are probably reached as a result of a two photon excitation of Nd³⁺. The S and A levels are also found to fluoresce at room temperature, and it is suggested that thermally assisted ion pair processes may be responsible for the population buildup in these levels at high temperatures. Transitions from the R (⁴F_3/2) levels to the ground state Z₁ and first excited state Z₂ (45 cm⁻¹) showed self-reversal at 77^°K. Owing to the simple geometry of laser excitation, the degree of self-reversal could be directly related to the oscillator strength of the transitions. This enabled an evaluation of the total f number of the Z-R transitions which could be compared with an earlier value obtained from direct absorption measurements.