Low Loss Mirrors

A low-loss mirror should reflect the laser beam with as little loss as possible. Low-loss mirrors therefore have reflectivities of 99.99 % or higher and are primarily used for frequency measurements of electromagnetic radiation and in cavity ring-down (CRD) spectrometers.

Fig.1:Low-loss mirror for optical contacting

Therefore, a manufacturer must pay particular attention to absorption sources in the coating system, such as stoichiometry errors or impurities (e.g. Fe, Cr, Cu).

It is also important to keep scattered light losses as low as possible. Their magnitude is mainly determined by the microroughness of the substrates and the inner interfaces as well as the volume scattered light of the layers.

Table 1:LAYERTEC currently achieves the following values (combination of LAYERTEC substrates and sputtered LAYERTEC coatings):

Wavelength	Absorbance	Scattered Light
355 nm	20 ppm	50 ppm
515 nm	2 ppm	6 ppm
1030 nm	<1 ppm	4 ppm
1550 nm	<1 ppm	3 ppm
2950 nm	20 ppm	2 ppm

As standard, the anti-reflective layer of the low-loss mirror is applied to substrate geometries from Ø 6.35 mm to Ø 50.8 mm.

We have broadband CRD measuring stations with which the reflection (ppm resolution) can be measured for different geometries.

Various mirrors are available as individual items in the LAYERTEC shop.