Optical coatings are pivotal in the field of photonics, designed to alter the transmittance, reflectance, and polarization properties of an optical substrate. For example, an uncoated glass surface typically reflects about 4% of the incident light. With the application of an anti-reflection coating, this reflection can be reduced to less than 0.1%. On the other hand, by using a reflective dielectric coating, reflectivity can be amplified to surpass 99.99%. These coatings can range from a single layer of metallic thin film, such as aluminum or silver, to a complex composition of materials, which may include metal oxides and rare earth compounds. The efficacy of an optical coating hinges on the number and thickness of its layers, as well as the refractive index disparity among them.
At DayOptics,
our expertise spans the spectrum of optical coatings, from fundamental
anti-reflective layers to intricate high-reflective and partial-reflective
configurations. Our offerings range from a single layer anti-reflective coating
to complex multi-layer dielectric assemblies. To ensure superior quality, we use a variety of different methods to produce high quality optical coatings.
Including Ion Beam Sputtering (IBS), Ion Assisted Deposition (IAD), and Magnetron
Sputtering (MS) and Electron Beam Evaporation (EBE)
Both Ion Beam Sputtering and Ion Assisted
Deposition stand out for delivering exceptional spectral performance,
remarkable durability, and consistent repeatability. However, it's worth noting
that these techniques, while delivering top-tier results, are more
time-intensive and carry a higher cost. For those seeking a more economical
approach, Electron Beam Evaporation (EBE) may be a cost-effective alternative.
Electron
Beam Evaporation
Electron
Beam Evaporation (EBE) represents the conventional technique within the realm
of Physical Vapor Deposition (PVD). Thanks to its high evaporation rate and
substantial capacity, it is the choice for keeping costs at a minimum. The
coating process takes place within a heated (250°C) high vacuum chamber,
utilizing an electron beam gun. Each electron gun emits a high-voltage electron
beam that converges onto a water-cooled, rotating crucible containing the film
material. This beam serves to liquefy and vaporize the material at an
approximate temperature of 2000°C.
Ion Assisted
Deposition
Ion-assisted
deposition (IAD) builds upon the electron beam evaporation (EBE) coating
deposition system, incorporating an additional plasma source. The plasma source
imparts the kinetic energy required for the formation of the deposited film
layer, leading to a denser microstructure that eliminates thermal drift. While
IAD maintains a high evaporation rate for cost reduction purposes, it also
offers reduced internal stress.
Magnetron
Sputtering - MS
Magnetron
sputtering (MS) employs magnetron plasma to sputter a metal layer onto a
substrate, followed by oxygen ions within the plasma to oxidize the metal
layer, resulting in the formation of a metal oxide. This technique produces
very dense and hard layers.
Ion Beam
Sputtering – IBS
Ion Beam
Sputtering (IBS) is the most advanced of PVD technology, especially crucial in
laser optics. The process involves sputtering layer material from a metal or
oxide target, which subsequently gets deposited onto a vertically rotating
substrate holder. In standard IBS machines, uniform layer distribution is
generally confined to an area of approximately 300mm in diameter. IBS
distinguishes itself as a "cold" deposition procedure, maintaining
chamber temperatures below 150°C.
Custom
Optical Coatings
The final
properties of a dielectric coating are intrinsically linked to the materials
chosen for the thin film layers, with their refractive index being of paramount
significance. Adjusting the thickness of these layers or altering their count
can profoundly modify the interference effects and, by extension, the overall
function of the thin film coating. In the realm of precision coatings, it's
imperative that the optical thickness of each layer is stringently controlled.
If you're
seeking the perfect optical coating design tailored to your specific needs,
look no further. The design will be influenced by factors such as the light's
wavelength, the operational environment of the optic, and your budget. Boasting
over 15 years of expertise in coating technologies, our design team is
well-equipped to guide you in identifying the custom optical coatings that are
optimal for your application.
