LAUSR

Abstract The optical, physical and mechanical properties of bulk crystalline materials might be improved by thermal annealing experiments. In this paper, we designed and self-manufactured a thermal annealing equipment for bulk crystalline materials. The temperature, stress distributions as well as airflow vectors in the equipment were carefully studied by the Finite Element Method. By using this equipment, we performed various of the thermal annealing experiments for KDP crystals in air, vacuum, N2 and H2, and we firstly found that its optical homogeneity can be greatly increased by annealing in H2, and whereas no obvious effect in air and N2. In addition, the thermal and stress field distributions in the annealing materials were also investigated, which has a guidance to avoid the local stress production and even break for the annealing materials.