Hi Michael, I’m assuming first that you’ve added the Birefringent catalog to your catalog set within the System Explorer? Unfortunately, it doesn’t look like OS has a built-in model for sapphire, at least not an obviously named one. You can see the full contents of the Birefringent catalog by going to Libraries > Materials Catalog

Assming that none of the names in that catalog are alternative names for sapphire, then you’d likely need to find a reference dataset describing the behavior of sapphire, then add sapphire to the catalog yourself. How to add new materials and glasses in OpticStudio – Knowledgebase (zemax.com). You’d need to define both SAPPHIRE and SAPPHIRE-E before you can use the model. In other words, you have to define the material’s behavior in both ordinary (SAPPHIRE) and extraordinary (SAPPHIRE-E) domains.