Deformation of the resonator of a neodymium glass laser due to a change in the polarizability of excited neodymium ions

A description is given of a method for measuring the change in the polarizability of neodymium ions due to their transitions from the ground state ⁴I_9/2 to the metastable level ⁴F_3/2. The results are reported for seven industrial laser glasses. The change in the polarizability is given as (0.9±0.1)×10^–25 cm³. These measurements are used to calculate the average oscillator strength of various allowed transitions between the 4f and 5d shells of the neodymium ion. It is shown that the formation of a lens in the active element, due to a change in the polarizability of neodymium ions, prevents full compensation of the resonator deformation by a suitable selection of the laser glass.