Stimulated emission investigations of effects of electron-phonon interaction in crystals activated with Nd3+ions

Stimulated emission spectroscopic methods were applied to investigate the electron-phonon interaction in Y
3
Al
5
O
12
and LaF
3
crystals activated with Nd
³⁺
ions. Temperature broadening and shifting of laser lines as well as the variation in the rate of nonradiative decay of the
⁴
I_{11/2}
state were studied. For the Y
3
Al
5
O
12
-Nd
³⁺
crystal, the analysis of the results on temperature broadening and line shifting reveal an effective Debye temperature of ∼600 K for the spectrum of impurity-active phonons. This value of T
D
very nearly corresponds to the energy of effective phonons (∼400 cm
^-1
) which are responsible for the nonradiative decay of the
⁴
I_{11/2}
state. For LaF
3
-Nd
³⁺
the effective T
D
values obtained by two different methods are 400 and 430 K, respectively. The temperature dependence of the threshold pumping energy for both laser crystals was computed theoretically. The physical factors governing this dependence are identified.