Polycrystalline Ba1-xSrxSi2 films with the Sr composition x varying from 0 to 0.77 were grown on transparent fused silica substrates by molecular beam epitaxy, and the effects of Sr addition on the indirect optical absorption edge E-edge were investigated. It was found that the E-edge value increases almost linearly with increasing x and reached approximately 1.40 eV when x was 0.52. When x > 0.6, the E-edge value almost saturates, and the formation of homogeneous Ba1-xSrxSi2 films became difficult. Composition separation was observed for x = 0.77. (c) 2007 Elsevier B.V. All rights reserved.