Crystal growth and spectroscopic characterization of Pr-doped KPb2Cl5 for mid-infrared laser applications

Abstract

Abstract We report on the purification, crystal growth, and infrared (IR) spectroscopic properties of Pr-doped KPb2Cl5 for applications in mid-IR solid-state lasers. KPb2Cl5 has a narrow phonon spectrum extending to only ∼200 cm−1, which leads to small non-radiative decay rates and long-wavelength IR emission from trivalent rare earth ions. The synthesis of Pr:KPb2Cl5 was based on the purification of commercial starting materials through baking under a dynamic vacuum, directional solidification, and multi-pass translation in a zone-melting system. The growth of the purified Pr:KPb2Cl5 material was then carried out through vertical Bridgman technique employing a two-zone furnace. Under 1540 nm diode laser excitation, Pr:KPb2Cl5 exhibited a broad mid-IR emission band centered at 4.6 μm, which was assigned to the 3H5→3H4 transition. The emission lifetime was determined to be 2.7 ms at room temperature. Based on Judd–Ofelt analysis, the radiative lifetime was calculated to be 26.9 ms, which results in a mid-IR emission quantum efficiency of ∼10% and a peak emission cross-section of 4.9×10−21 cm2.