highreflective

Highreflective is a term used in optics to describe surfaces or coatings with exceptionally high reflectance within a defined spectral range. In practice, highreflective coatings reflect the majority of incident light while transmitting or absorbing only a small fraction. The term is commonly used interchangeably with high-reflectivity or HR coatings, especially when referring to mirrors for lasers, interferometers, and optical cavities.

Highreflective coatings are often implemented as dielectric multilayer stacks or, less commonly, as metallic coatings. Dielectric HR coatings achieve very high reflectivity by alternating layers of materials with differing refractive indices, typically a high-index material such as Ta2O5 or TiO2 and a low-index material like SiO2. A quarter-wavelength stack at the design wavelength yields constructive interference that enhances reflectance. Broadband HR coatings use many more layer pairs to maintain high reflectivity across a wider spectral band. Metallic coatings, such as aluminum, silver, or gold, can provide broad reflectivity but often with higher absorption or wavelength-dependent performance and sometimes require protective overcoats.

Manufacture of highreflective coatings involves precise deposition techniques, including physical vapor deposition, sputtering, ion-beam sputtering, or atomic layer deposition. Achieving low absorption, minimal scattering, and tight thickness tolerances is essential to reach target reflectance. Coating durability, environmental resistance, and contamination control are important for long-term performance, especially in high-power laser and space environments.

Applications of highreflective coatings include laser resonators, optical cavities, telescope and instrument mirrors, interferometry, and photonic devices. Performance is influenced by wavelength, angle of incidence, and polarization, underscoring the need for design and testing tailored to the intended use.