Fig. 1: Length scale relationships important for achieving gain in anisotropic ceramics. | Light: Science & Applications

Fig. 1: Length scale relationships important for achieving gain in anisotropic ceramics.

From: Gain in polycrystalline Nd-doped alumina: leveraging length scales to create a new class of high-energy, short pulse, tunable laser materials

Fig. 1

a Light is scattered at grain interfaces in ceramics with large crystallites because randomly oriented grains represent discontinuities in refractive index. RE segregation (represented as a close-packed monolayer) at the grain boundary on a section of Al2O3 (the blue atoms are Nd, those in white are O, and those in black are Al). b Scattering efficiency decreases significantly when pump (λ1) and emitted light (λ2) wavelengths are smaller than the grain size, permitting low optical losses. Small grains also permit spreading out of RE dopants at grain boundaries, increasing average interionic distance,\(\tilde l\) allowing for optical gain. c A close-packed arrangement of dopant l = 0 and one with realistic interionic distance for gain (l = 1 nm). d Calculation of grain size necessary to accommodate all the dopants for a given dopant arrangement and concentration on the grain boundary, deff vs. grain size using Eq. 4 for two concentrations and arrangements shown in (c)

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