Analysis of giant pulse amplification in Nd3+doped glass

In a study of the mechanism of giant pulse amplification in Nd
³⁺
doped glass, the following measurements have been made: 1) energy extracted from an amplifier as a function of the input energy, 2) relative fluorescence intensity at 0.9μ in a slab, pumped by the emission of a ruby laser, and 3) gain variation after the transit of an intense, short, rectangular pulse. The experimental results have been compared to theoretical results from a model where both metastable and terminal levels are regarded as comprising two components. The unknown multiplicity of the lower component of the terminal level g
11
appears as a parameter. It is assumed that during the pulse duration, Boltzmann distribution is maintained between the components of each level. A finite terminal level lifetime τ
n
may be introduced in the model. Best agreement is obtained with the following values of the parameters: amplification cross section
\sigma_{21}\simeq 1.8.10^{-20}
cm
²
,
g_{11} = 1
or 2, and
\tau_{11} \geq 100
ns.