Technical Coating Data for:

• Bare (Unprotected) Aluminum Mirrors
• Bare (Unprotected) Gold Mirrors

Metallic coated optical mirrors are coated with various metals to provide reflectivity across the UV, VIS, and IR spectra making them an excellent choice for a wide range of applications. When choosing a metallic coating, one should carefully consider the following:

• Intended wavelength of use
• Required reflectance
• Environment in which the mirror will be used

Advanced Optics manufactures optical mirrors that offer reflectivity from 190nm – 20µm. Please visit our technical protected metallic coatings page to learn more about mirrors with a protective overcoat.

Bare (Unprotected) Aluminum Mirrors

Bare aluminum mirrors provide good reflectivity from the near UV into the IR spectrum, with R_avg > 91% from 200 – 2000nm and Ravg > 96% from 2 – 10µm.

Unlike protected aluminum mirrors which have a layer of silicon monoxide or dioxide that acts as a hard barrier, the soft aluminum on these mirrors has no overcoat to protect them, making them difficult to clean without damage and susceptible to oxidization over time. Therefore, bare aluminum mirrors are best suited for use in climate-controlled environments where they will be enclosed with limited handling.

The advantage of a bare aluminum mirror is that the overcoat does not cause enhanced interference or absorption of light at 880nm. In addition, these mirrors are not affected by the water bands in the NIR and IR spectra caused by a protective overcoat. This makes them the mirror of choice for some systems such as spectrophotometers.

Please visit our optical mirrors page to see our in-stock bare aluminum optical mirrors.

Bare Aluminum

Bare (Unprotected) Gold Mirrors

Bare gold mirrors provide good reflectivity from the NIR through the IR spectrum, with R_avg > 98.5% from 1 – 10µc.

Bare Gold

Unlike protected gold mirrors which have a thin dielectric layer that adds protection from abrasion, bare gold is soft and cannot be easily cleaned without damage.

The advantage of bare gold over bare aluminum (and other metallic coatings) is that it is chemically inert and therefore will not oxidize over time. This makes bare gold mirrors useful for applications in the IR spectrum that cannot tolerate the interference or absorption of light around 2.8µc and 8-9µc caused by the protective overcoat.