Optical coatings for high power lasers with ALD

It’s hard to believe that lasers were initially called ‘a solution looking for a problem’ when first developed in 1960 by Theodore Maiman. Today, these powerful beams of energy are used in multiple applications and industries, such as surgical treatments, cutting, welding, electro-optical countermeasures, fluorescence microscopy, laser printers, optical discs, barcode scanners, and fiber-optic communication.

Coating optical lenses and prisms to redirect light

A laser beam is basically light waves that have been concentrated and redirected multiple times to create one powerful beam. Optical lenses and prisms are used to redirect the light waves, they’re also used to allow a specific light wave to pass through, or to reflect specific wavelengths.

Prisms and optical lenses alone cannot do all of this manipulation of light – it’s the specifically designed coatings on the prisms and optical lenses that are crucial.

The type of optical coating depends on what kind of outcome is needed. For example, if you need to reflect a particular type of wavelength of light, a specific optical coating is designed that will reflect a major percentage of light and transmit a minor percentage of light over this specific wavelength.

Optical ALD coating for complex 3D shapes

Due to the complex 3D shape of optical lenses, they cannot be coated with high uniformity using conventional technologies like PVD. The best way to conformally coat complex 3D shapes is with ALD technology. Optical ALD coating is created one layer at a time, resulting in pinhole-free conformal films.

With ALD you can achieve high quality optical coatings on even the most complex-shaped parts. The most common optical coating materials with ALD are SiO₂, Al₂O₃, and TiO₂.

Optical ALD coatings reach good laser induced damage threshold

Optics are tested to see what their laser induced damage threshold (LIDT) level is to determine the aptness of the optic for a specific application. This basically means that the optic is zapped first with low, then with high energy beams, and the results are examined to define what damage threshold level the optic has.

ALD multilayer coatings can reach a good LIDT level. The example below shows the damage threshold of a 4.1 μm thick Al₂O₃ / TiO₂ multilayer reflector sample:

Why choose Beneq ALD for high power lasers

1. Conformal and uniform coatings on 3D optic surfaces – high aspect ratio (HAR) surfaces, high curvature lenses, prisms and tubes.
2. Good LIDT preformance.
3. Precise and repeatable thickness control with atomic scale accuracy.
4. Dense and pinhole free films can also serve as barrier layers.
5. Beneq has pioneered expertise in optical coatings by ALD, knows the materials well, and has the competence for designing and characterizing optical coatings
6. Beneq supports various substrate sizes – from mm scale to meters.

Film uniformity, conformality and repeatability with the possibility of coating complex surfaces make ALD technology ideal for optical applications.