Sapphire lenses for industrial applications

Made from a single aluminium oxide crystal, sapphire-based lenses are optically transparent from infrared through visible to UV light. They offer the highest strength of all optical window materials except diamond, retaining all mechanical proprieties across a wide temperature range from cryogenic (-150°C and below) to more than 2,000ºC, and also feature the highest melting point at around 2,040ºC.

Their strength and hardness mean they will not suffer surface damage or de-vitrification caused by extreme thermal cycling and they are resistant to the vast majority of commonly encountered chemicals. High radiation systems also offer resistance to solarisation (UV radiation darkening). The material’s high dielectric constant and low loss tangent makes it suited to low-loss, long-wavelength windows and electrical insulators.

Sapphire lenses are supplied either pre-metallised for in-house braze assembly by customers, or as a complete unit with metal housings produced to customer specifications. The latter provides a hermetic seal suited to ultra-high vacuum (UHV) applications which can be subjected to repeated thermal cycling, and still maintain a helium leak rate equal to or less than 1x 10-9 mBar l/sec. Lenses can be supplied flat, or with single or double convex faces.

Further applications for which this technology is suitable include optical windows for infrared thermal detection; windows for semi-conductor plasma and chemical etching; and windows for furnaces, pyrometers and other high-temperature processes.