Modeling and CW operation of a quasi-three-level 946 nm Nd: YAG laser

A model is developed for an end-pumped quasi-three-level laser with population in the lower laser level at equilibrium such as for transitions to the manifolds
⁴
I
9/2
in Nd
³⁺
,
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I
15/2
in Er
³⁺
,
⁵
I
8
in Ho
³⁺
and
³
H
6
in Tm
³⁺
. It is shown that the effect of residual lower laser level population on laser operation can be treated as a saturable loss. Room temperature operation on the
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F
3/2
-
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I
9/2
transition in Nd:YAG under CW dye laser pumping has been demonstrated with a threshold as low as 11.5 mW incident power and a slope efficiency of 7 percent with 0.3 percent output coupling. Performance is limited by the low output coupling and diffraction loss.