Thermal and spectroscopic characterization of Yb:Lu3Al5O12 crystal from 10 K to 300 K for excellent performance laser

Abstract

Temperature-dependent thermal and spectroscopic properties of Yb:Lu₃Al₅O₁₂ crystal from 10 K to 300 K have been investigated for cryogenic laser design. Thermal properties, such as thermal expansion coefficient (TEC) and thermal conductivity are presented. The TEC decreases progressively as temperature drops from room temperature to 10 K. Particularly, the TEC is found to be about zero around 25 K. The peak thermal conductivity is 212.6 W/mK at ∼ 18 K, which is about 3.6 times more than that at 77 K and 30 times more than that at room temperature. Moreover, the spectroscopic properties including absorption cross sections, stimulated emission cross sections ${\sigma }_{\mathrm{SE}}$ and fluorescence lifetime have been measured. The ${\sigma }_{\mathrm{SE}}$ at zero thermal expansion (ZTE) temperature is 18.52 × 10⁻²⁰ cm², which is almost an order of magnitude than the result at 300 K, suggesting a more efficient operation. Based on the large thermal conductivity, zero TEC and high emission cross section around ZTE temperature, high-power high-beam-quality and highly efficient Yb:LuAG lasers can be anticipated.