Method for preparing high-purity REE-doped chalcogenide glasses for bulk and fiber lasers operating at ∼ 5μm region

•A method for preparing high-purity REE-doped Ga - Ge - Sb - Se glasses is developed.•Ge, Sb and Se batches are loaded into the silica-glass reactor by reactive distillation method.•REEs are loaded into the reactor in the form of their iodides together with Ga by the chemical vapor transport (CVT) method.•The CVT of Ga and REEs reduces the content of all controlled impurity groups in glasses.•Bulk and fiber samples of prepared glasses demonstrate, for the first time, mid-IR laser generation with practically significant output power.