Infrared Coatings

Infrared coatings is an optical coating optimized for the infrared region, between 2.5μm(2500nm) and 16μm. Optical thin films are vacuum deposited on the substrate to enhance performance. An AR coating, otherwise known as an anti-reflection coating, will decrease reflection on a substrate and may be used to increase transmission. Reflective coatings are used on beam splitters to increase reflectance and create a mirror surface, where infrared radiation is reflected back to the source or at an angle.

At Shanghai Optics we have more than 55 years of experience in producing high quality optics, and infrared coatings are one of our areas of expertise. If you are unsure as to what coating best fits your application, don’t hesitate to call us: we’d be happy to provide the design help and consulting you need to achieve ideal results. Choose from our wide range of in stock options, or work with us to come up with custom coating services that meet your individual needs.

Applications of Infrared Coatings

Infrared coatings are primarily used in industrial and medical laser equipment, for CO2 laser, Er:Yag laser, Co and HF lasers.

High Energy CO2 Laser Coatings

High energy CO2 laser coatings are optimized for 10.6μm. Typically ZnSe or GaAs lenses are used for this application, and a special durable coating is needed: an ordinary antireflection coating would quickly get damaged by the high power laser beam.  High efficiency and a high damage threshold are both key properties of CO2 laser coatings.

Er:Yag Laser Coatings

Er:Yag lasers are solid state lasers which operate at 2.94 microns. They are chiefly used in medical and dental applications, and a series of infrared mirrors are an important part of the laser setup. These may be metal mirrors or mirrors formed by optical thin films, vacuum deposited on the substrate.  Internal mirrors (resonators) form a reflective resonator around the Nd:YAG crystal and in doing so generate, maintain, and amplify the laser beam.  External mirrors include bending mirrors, which are used to direct the laser beam toward the subject. These mirrors feature dielectric coatings which reflect most of the laser beams.

Internal mirrors include output couplers, which have two coatings: an anti-reflective coating to improve transmission as a partially reflective coating on the inner surface. This coating is meant to reflect a given percentage of the beam to the resonator.

Another type of internal mirror is a rear mirror, which reflects nearly all of the laser beam back through the crystal to be amplified. While the outside surface does not need to be coated, the inside surface has a high reflection coating that reflects 99% or more infrared light.

We carry in stock Calcium Fluoride and Sapphire Crystal lenses, with a special infrared coating that exhibits high reflectivity (less than 0.2 percent light reflected).

Other Infrared Applications

An HF Laser is a infrared chemical laser, and operates at 2.7-2.9 µm or (with deuterium in the place of hydrogen) at 3.8 µm.  The Tactical High Energy Laser and MIRACL lasers are of this deuterium fluoride type.

At Shanghai Optics we also provide a variety of infrared thin film coatings for infrared imaging systems. Magnesium fluoride windows are available with anti reflective coatings optimized for 3.5-4.8μm, with a transmission of greater than 95 percent over those spectral regions.  Our ZnSe/ZnS/Ge Substrate Lens comes with a range of coating optimized for two spectral regions: 3.5-5.5μm, where transmission is greater than 98%, and 7.5-11.5μm, where transmission is greater than 97%.  Silicon lenses are available with coatings optimized for  3.5-5μm (transmission 98%) and 7.5-11.5μm (transmission greater than 60%).