Partially reflective coatings are used for substrates, which are used as output couplers or beam splitters in laser systems.

High power dielectric coatings can be manufactured on a standard basis for the wavelength range from 193 nm to 5 µm. For the cw/fs coating this wavelength range extends from 450 nm to 2 µm.

Ouput couplers are mainly used inside resonators to extract the laser beam. Through a suitable choice of the degree of reflection the quality of the laser resonator is optimized. Output couplers are also commonly used in attenuation. The back side of output couplers is typically equipped with an AR coating to minimize the loss of the transmitted beam.

Output Couplers for Excimer Lasers

For mirrors that are used outside of the excimer laser resonator, the standard coating is usually applied to fused silica substrates. If the mirrors are used inside the resonator, the coatings have to be chlorine or fluorine resistant because they are exposed to the aggressive laser gas. In such a case, it is important to use CaF₂ or MgF₂ as the substrate material.

Output Couplers for Solid-state Lasers

These coatings are primarily applied to BK7 substrates. For systems with very high power densities, the coatings can also be applied to fused silica.

Output Couplers for cw/fs Mirrors

These coatings are mainly applied to fused silica substrates. Some mirrors are also available on BK7 substrates. As an option, the rear side can be AR coated to prevent losses.

These optics are mainly used in external beam guidance to separate the beam into clearly defined parts. In standard coatings, the degree of reflection is normally only guaranteed for one polarization. Additional specifications can be arranged upon request. The back side of beam splitters is typically equipped with an AR coating to minimize the loss of the transmitted beam.

Beam splitter mirrors

Beam splitters are offered for high power and cw/fs lasers. Quartz is normally used as substrate; VUV-quartz is preferred for 193 nm, for cw/fs lasers it is also common to utilize BK7 substrates.

Variable Beam Splitters

Challenging applications require tolerances of less than +/-1% when splitting a beam. Furthermore, there are applications in which different losses occur in each beam path after adjustment. For such cases a beam splitter was developed that can be actively adjusted. The variable beam splitter has a position-dependent reflection profile. By moving the beam splitter one can obtain a reflection value between 45% and 55% depending on the position. The values can be continuously adjusted.