White Papers
Optimizing Optical Thin Film Filters: Impact of Angle of Incidence and Opening Angle
Optical thin film filters are critical components in numerous optical systems, serving various applications from spectroscopy to imaging. Understanding …
Comparative Analysis of Optical Thin Film Filters Fabricated via Sputter Technology and Physical Vapor Deposition
Optical thin film filters are essential components in various optical systems, offering precise wavelength selectivity and …
Our Coating Technologies
In the manufacture of our optical filters, we employ both conventional Physical Vapor Deposition (PVD) multilayer coatings combined with a high-quality encasing technique to ensure environmental stability, Plasma-Assisted Deposition techniques to produce hard coatings that exhibit unrivalled durability in harsh environments, and Sputter Coatings to produce state of the art filter solutions. We also offer e-beam evaporation of various materials for the manufacture of special thin-film coatings.
Sputter Technology
Sputtering is the newest technology, and the advantage here is a very good film quality with low scattering and highly reproducible deposition control. With this technology, thinner layers and a high number of layers can be deposited precisely.
Plasma-Assisted Deposition Techniques
A conventional hard coating is manufactured by heating up substrates to ~300C and using oxides evaporated from a crucible by an electron beam gun. The result is a hard coating that needs no protection from atmospherically exposure or physical damage. The coating, however, still suffers from a columnar structure (the particles still arrive at the substrate with an energy of ~ 1 eV) where water can penetrate into. This will shift the optical properties, because of a shift in the refractive indices and is therefore not a desirable solution when a certain degree of precision in the coated filter is required. Ferroperm Optics has developed its own unique technology to overcome the drawbacks of conventional soft and hard coated thin films. By utilizing an innovative technique to produce an O2-plasma in the vacuum chamber during the deposition of the oxide-materials, we can completely remove the columnar structure and thereby deposit a uniform, 100% dense thin film. The basic idea is that the plasma in the chamber forms an excess negative charge on the substrates, which will attract the (by the plasma) positively ionized evaporated particles. These will then impinge with a higher energy than in the conventional case and by – in a delicate way – balancing this energy to remove the columnar structure, but not induce tensile stress in the films, we do manufacture a very stable, 100% dense thin film with very low stress. This coating technology has been used in various applications for more than 20 years and is thus thoroughly tested in the field.
Physical Vapor Deposition
This is the standard technology used in optics houses around the world. A great variety of materials can be used, and evaporation is taking place by using two different physical vapour deposition techniques: Resistance evaporation and electron beam gun evaporation. Particles evaporated such a way will form a cloud in every direction not obstructed and arrive at the substrate carrying a relatively low energy, around 1 eV. This unfortunately leads to a porous structure in the thin film. A filter coated without further assisted energy thus suffers from a short lifetime when exposed to the atmosphere. The porous structure of the film will absorb water and slowly degenerate while the optical property changes. Therefore, sealing of the filter is important to eliminate this degeneration. Ferroperm Optics has constantly since the establishment of the thin film division in 1977 continued the development of the sealing and cementing technique of our soft coated filters and therefore typical lifetimes are now at least 5 years. This has brought us in the front line compared to other market players.
Evaporation of Metal Films
Ferroperm Optics manufacture first surface aluminium, silver and other metal mirrors by e-beam evaporation or resistance heating in a new vacuum chamber dedicated to metal evaporation. The metal layers are often protected with a thin hard layer of dielectric overcoat to protect the metal and enhance the reflection. We also have a gritless ion source available to further assist the deposition if necessary. Our metal mirrors are of a very high quality and used by many of our customers in various applications where high reflection is needed.