Amplification cross section of the 1.052-µ transition of Nd3+in POCl3- SnCl4-(H2O) system by three different methods

We report the measurement of the amplification cross section σ
21
of the Nd
³⁺
ion in the POCl
3
-SnCl
4
-(H
2
O) system by three different methods. The first is based on the simultaneous measurement of the variation of fluorescence and
Q
-spoiled laser emission. The second is purely spectroscopic. The third is based on the measurement of k
12
at several temperatures. The two last methods give similar results. The most probable value is
\sigma_{21} = 8.5 \times 10^{-20}
cm
²
. An explanation for the lowest value
\sim 6 \times 10^{-20}
cm
²
found with the first method is given.