External turning mirrors should be made to the same standards as intra-cavity optics. Even outside the cavity, scatter and absorption can cause severe problems in high energy laser systems.

Turning mirrors are optimized for use at the laser wavelength at or close to 45° angle of incidence. They are typically designed to have 99.5% minimum reflectance of the p-polarized component. At 45° the s-component of polarization is more efficiently reflected resulting in a broader bandwidth for this state of polarization.

Even though these are reflecting components the substrate is usually made of a substance which transmits at the laser wavelength to minimize absorption heating.

Sometimes (for example with alignment beams) it is desirable to reflect more than one wavelength at the same mirror surface. In this case a dual wavelength mirror can be used. Once again the mirror coating is specifically optimized for use at the two appropriate wavelengths. The second wavelength has a lower, but still useful, reflectivity, usually about 85%.

We can provide turning mirrors for almost all laser types.