Glass-ceramics have useful properties for both passive & active photonics applications which are difficult or impossible to achieve in glasses of other materials. One such property is a negative thermal expansion coefficient, which is useful in athermalization of fibre Bragg gratings, devices that can be used in a variety of optical components. Transparent glass-ceramics can display similar luminescent properties to those of single crystals, yet can be fabricated into fibre form with rapid glass-forming techniques. Rare-earth-doped fluoride nanocrystals have been precipitated in oxyfluoride glass-ceramics with resulting luminescent efficiency superior to those of less stable RE-doped fluoride glasses. Recently, transition metal-doped glass-ceramics, particularly Cr: fosterite, have demonstrated broad near infrared luminescence.
