Anomalous gain enhancement was observed in thin indium tin oxide-, zinc selenide-coated, and uncoated Fe-doped lithium niobate (Fe:LN) slabs. Coating dependent strong scattering near the surface normal was also observed and investigated in these slabs. The correlation between mid-wave IR oscillation and gain and the enhancement of the scattering near surface normal was evidenced in several supported experiments. A tentative model based on quasi-two-dimensional diffusive amplification was proposed to elucidate these findings.
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