Float zone growth and spectroscopic properties of Yb:CaYAlO4 single crystal for ultra-short pulse lasers

Abstract Yb:CaYAlO 4 single crystals were grown by the floating zone method and their spectral properties were investigated. Void formation was effectively suppressed by using a feed rod of Y-rich composition with the aid of a double zone-pass technique. For the oxygen excess composition of Yb:Ca 0.9925 Y 1.0075 AlO 4.00375 , a void-free crystal was obtained by performing only the double zone-pass. On the other hand, for cation-deficient type of Yb:Ca 0.9925 Y 1.005 AlO 4 , void-free crystal could not be obtained by performing the double zone-pass. The void formation is attributable to the constitutional supercooling caused by segregation of main constituents of Y and Ca, and the congruent composition may exist in the Y-rich region with existence of interstitial excess oxide ions. The absorption cross section for σ-polarization was slightly larger than that for π-polarization, which is reasonable on the basis of the crystal structure of CaYAlO 4 .