Abstract

Yttrium orthoaluminate (YAlO₃, shortly YAP) is a well-known laser host matrix for doping with rare-earth ions. It crystallizes in the same binary system as Y₃Al₅O₁₂ but possesses an orthorhombic structure (sp. gr. D¹⁶_2h – Pnma). Thus, YAP is an optically biaxial with anisotropic absorption / emission properties of the dopant ions leading to polarized laser emission. It features good thermal properties and low phonon energies which are essential for laser operation in the mid-infrared spectral range. Recently, efficient lasers based on Er³⁺ and Ho³⁺-doped YAP crystals operating at ~3 µm according to the ⁴I_11/2 → ⁴I_13/2 Er³⁺ and ⁵I₆ → ⁵I₇ Ho³⁺ transitions, see Fig. 1(a), were demonstrated [1,2]. Still, the information on the polarization anisotropy of stimulated-emission (SE) properties of these ions is scarce. In the present work, we report on polarized SE properties of Er³⁺ and Ho³⁺-doped YAP crystals at ~3 µm.

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