Silicon material has good thermal conductivity, low density, high hardness, and good light transmission performance at 1-7um. Monocrystalline silicon is commonly used for 3-5um mid-wave infrared optical windows and substrates for optical filters, and is also a common material for laser reflector substrates.

Meniscus lenses includes positive meniscus and negative meniscus lenses. A meniscus lens has one side of the lens that is convex and one side that is concave. It can be a converging lens or a diverging lens, determined by the refractive index, curvature and radius together. Widely used in photographic systems, projection systems, imaging systems, optical viewfinders, and laser measurement systems.