DEMONSTRATE GROWTH OF CR:LISRALF6 (CR:LISAF) CRYSTALS FOR LASER APPLICATIONS

TWO NEW TUNABLE LASER MATERIALS, CR:LICAALF6 (CR:LICAF) AND CR:LISRALF6 (CR:LISAF), DISCOVERED AT LAWRENCE LIVERMORE NATIONAL LABORATORY HAVE SHOWN INTRINSIC EFFICIENCY COMPARABLE TO ALEXANDRITE; HOWEVER, THEIR FULL POTENTIAL LASER PERFORMANCE IS LIMITED BY THE QUALITY OF CRYSTALS AVAILABLE. THE ABSORPTION AND EMISSION CROSS SECTION OF CR:LISAF ARE A FACTOR OF 4 LARGER THAN CR:LICAF. THE MAJOR IMPEDIMENT TO THE COMMERCIALIZATION OF CR:LISAF LASERS IS THE HIGH SCATTER LOSS AND CRACKING OF CRYSTALS. THE PROPOSED PROGRAM IS TO ADAPT THE HEAT EXCHANGER METHOD (HEM(STABILIZER)) FOR GROWTH OF CR:LISAF CRYSTALS. LOW TEMPERATURE GRADIENTS WILL BE UTILIZED TO MINIMIZE DEFECTS AND SCATTERING LOSSES DUE TO VARIATIONS IN STOICHIOMETRY. THE CRACKING PROBLEM IS ATTRIBUTED TO NEGATIVE THERMAL EXPANSION COEFFICIENT ALONG THE C AXIS FOR CR:LISAF AND STRESS IN THE CRYSTAL AFTER GROWTH. THE SHAPE OF THE SOLID-LIQUID INTERFACE DURING GROWTH BY HEM WILL BE CONTROLLED SUCH THAT SOLIDIFICATION OCCURS OFF THE INTERFACE IN PREFERENCE TO OFF THE CRUCIBLE WALL. IN SITU ANNEALING WILL BE CARRIED OUT TO MINIMIZE STRESS AND TEMPERATURE GRADIENT ON THE CRYSTAL DURING COOLDOWN. DETAILED CHARACTERIZATION OF CRYSTALS WILL BE CARRIED OUT ATALLIED-SIGNAL INC. THIS GROUP HAS EXTENSIVE EXPERIENCE IN CZOCHRALSKI GROWTH OF CR:LISAF AND IS A LEADING PRODUCER OF TUNABLE LASERS.