Lanthanum fluoride is sometimes used as the "high-index" component in multilayer optical elements such as ultraviolet dichroic and narrowband mirrors. Fluorides are among the most commonly used compounds for UV optical coatings due to their relative inertness and transparency in the far ultraviolet . Multilayer reflectors and antireflection coatings are typically composed of pairs of transparent materials, one with a low index of refraction, the other with a high index. There are very few high-index materials in the far UV. LaF₃ is one. The material is also a component of multimetal fluoride glasses such as ZBLAN. It is also used (with europium trifluoride, EuF₃) in fluoride selective electrodes.