Abstract

The optical properties of Nd³⁺ in CaF₂, SrF₂, and BaF₂ have been investigated in order to determine if these materials are useful as laser-pumped amplifier media. The CaF₂:Nd crystal was found to not be useful because the impurities tend to cluster at very low concentration, leading to the formation of nonluminescent centers. On the other hand, the Nd³⁺ centers in BaF₂ exhibit unacceptably low transition strengths. SrF₂:Nd appears to have adequate absorption strength, and, in addition, to have a remarkably long emission lifetime of 1280 μs. A maximum doping of 0.20 atomic % Nd³⁺ can be tolerated in SrF₂ without the occurrence of detrimental clustering. The peak emission cross section of SrF₂:Nd is 1.7 × 10⁻²⁰ cm² at 1036.5 nm. Direct measurement of the gain spectrum of SrF₂:Nd³⁺ reveals the presence of the ⁴F_3/2 → ²G_9/2 excited state absorption lines, although the impact on the emission cross section is minor.

© 1990 Optical Society of America