Growth of a New Mid-IR Laser Crystal

70606S02-II Rare-earth-doped potassium lead pentachloride crystals are sought as new mid-IR lasers for detecting airborne chemical species for national security applications, but a reproducible growth technique is not yet available. Achieving high quality crystals also will require suitable raw material preparation techniques. This project will develop purification and growth methods capable of producing the high quality crystals needed for efficient, diode-pumped lasers that function at important mid-IR wavelengths. First, pure starting materials, are essential for the growth of these crystals, will be produced using the material preparation techniques of hydrochlorination and horizontal zone melting. Then, vertical Bridgman and Czochralski methods will be used to grow crystals for evaluation. In Phase I, commercial-lead-chloride and erbium-chloride powders were purified by zone refining and hydrochlorination. The powders were used to grow an erbium-doped single crystal of potassium lead pentachloride by the vertical Bridgman technique. In Phase II, the vertical Bridgman technique for growing erbium-doped potassium lead pentachloride will be optimized. The possibility of applying the Czochralski technique to grow large crystals in a reactive atmosphere will be investigated. The laser properties of single crystals grown in the Phase II project will be demonstrated and optimized. Commercial Applications and Other Benefits as described by awardee: New lasers for detecting gaseous and biological agents should emerge from this research. The new crystal should provide unique direct laser transitions in the mid-IR where atmospheric interference can be avoided. Commercial laser companies and defense organizations should benefit from these compact, high power, diode-pumped systems.