IAD
Ion-Assisted Deposition

Thermal evaporation under vacuum is the standard process by which dielectric coatings for laser optics are produced. An important parameter which affects coating quality is the kinetic energy of the atoms adsorbed on the substrate. If this energy is too low the result is a porous layer which is both mechanically and chemically unstable. Further, the optical properties of such layers may be insufficient for laser applications.

This problem may be partially overcome by heating the substrate to approximately 250°C as the coating is applied. However the optimum temperature cannot be reached due to process constraints and this technique also precludes the use of temperature-sensitive substrates.

Ion-assisted deposition, now routinely used at Laser Components GmbH, offers the solution to this problem. In this technique, the newly-deposited coating layer is subjected to a stream of ions (O, Ar, Xe). These ions transfer energy to the adsorbed surface atoms, thereby increasing their kinetic energy and resulting in a more compact, non-porous layer.

No heating of the substrate is required, which enables this technique to be applied to sensitive substrates at temperatures well under 100°C. A few examples of application areas which benefit from IAD are described below.

High power coatings for Nd: YAG, Ho:YAG and Er:YAG

The denser layers made by IAD contain much less water than conventional coatings. This leads to an increase in damage threshold, particularly in the 2-3 µm region.

Thermally stable layers

The use of conventional coatings in high power lasers can lead to significant changes in transmission due to heating of the coating layers. This effect is greatly reduced in the case of IAD coatings due to the dense layer structure.

Coatings on optical fibres

Laser Components GmbH is well known for its range of high quality optical fibres and related products. IAD allows the end surfaces of optical fibres to be coated even if the fibre is equipped with buffer, connector etc. Such coatings include antireflection, partial reflection of filter coatings.

Coatings on temperature-sensitive substrates

The low temperatures used in IAD mean that coatings may be easily applied to plastic optics, mounted optics, cemented optics, crystals or other sensitive components. Antireflection, totally or partially reflecting and many other coating types are possible.

Mark Day: 01245 491 499