Optical Studies on Hot-Pressed Polycrystalline CaF2 With Clean Grain Boundaries
It has been demonstrated that with careful powder preparation and vacuum hot-pressing techniques, optical-quality polycrystalline CaF2 can be made, the density of which is 99.998% of theoretical. The transmittance, refractive index, and optical homogeneity of hot-pressed and single-crystal CaF2 are compared and shown to be virtually identical. Dysprosium-doped CaF2 lasers have been operated in both the hot-pressed polycrystal and single-crystal forms. The thresholds for laser oscillation in the two forms are compared. It can be inferred from the data presented that clean grain boundaries in an isotropic material do not measurably affect the ordinary optical properties.
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