ZBLAN

ZBLAN is a family of heavy metal fluoride glasses with a nominal composition of ZrF4-BaF2-LaF3-AlF3-NaF. The name ZBLAN derives from the principal fluorides in the melt: zirconium fluoride, barium fluoride, lanthanum fluoride, aluminum fluoride, and sodium fluoride. These glasses are engineered to combine good infrared transmission with the processability of glass, offering advantages over many oxide glasses in the mid-infrared region.

ZBLAN glasses exhibit a wide optical transmission window, typically from about 0.25 micrometers in the visible to around 5 micrometers in the mid-infrared. They possess relatively low phonon energy, which helps maintain radiative efficiency for rare-earth dopants such as Er3+, Pr3+, Ho3+, and Tm3+. This makes ZBLAN suitable for fiber lasers and amplifiers operating in the near- to mid-infrared. The refractive index of ZBLAN is approximately in the low 1.5 range, varying with composition and wavelength.

Manufacture and processing of ZBLAN require careful control of moisture and temperature. The glasses are melted and cast in dry, inert conditions to prevent hydrolysis and crystallization. Processing temperatures are high for fluoride glasses, and the material must be cooled and reshaped to avoid phase separation or crystallization. Fiber drawing is performed from preforms under controlled atmospheres to preserve amorphous structure and optical quality.

Limitations include chemical sensitivity to moisture, leading to hydrolysis if exposed to water during handling. ZBLAN is also more prone to crystallization and mechanical brittleness than many oxide glasses, which can increase optical losses and reduce durability. Nevertheless, its unique infrared transparency continues to drive research and applications in mid-infrared fiber optics and laser systems.