Many users of UHV systems frequently make use of view port either to view samples within the vacuum system or to
couple radiation for sample processing and/or measurement. Depending on the application, view ports utilize a range
of window materials from simple glass for optical viewing to specialized materials that are tailored to a specific
application. These windows are mounted in ConFlat flanges to form the view port assembly. They are available in a
variety of standard sizes to best fit the customer’s particular vacuum system requirements. Additionally, view ports
provided at SPI are guaranteed to be fully compatible with UHV systems and include confirmed high temperature bake
ratings and vacuum leak specifications.
Where the best window transmission characteristics are important, all view ports can be supplied with windows that include custom
anti-reflection (AR) coatings. In situations where concerns for X-ray leakage exist, view ports can also incorporate lead
glass shielding to block any stray radiation.
The view port product contains window material that can be glass (Kodial), quartz, and sapphire or even zinc selenide,
either uncoated or coated with one of our standard antireflection coatings. The choice of the window material depends on
the part of the eletronmagnetic spectrum that is on interest to the customer. We have view ports that are optimized for
use in the UV, other for the visible and still others for use in the far infrared. The actual choice is dependent on the customer’s needs.
The choice of the anti-reflection coating depends on what wavelength one is working with, since the coating increases the
transmittance (or reduces the reflection) only within a portion, or “band” of the spectrum. Where several percent reflections
from the window face is not a problem, then no coating is required. The next level of performance is a one quarter wavelength
optical thickness, or “1QWOT” AR coating. This is a durable broad band coating that reduces reflection to few percent over
large portion of the window transmission band. Where even better broad band performance is required, broad band AR, or “BBAR”
multi-layer coatings can be supplied which can further reduce reflection to less then one percent over a wide band of the spectrum.
Finally, when one is working with a single wavelength or narrow band, then a notch, or “VAR” multi-layer coating can virtually
eliminate reflection at that particular wavelength (very popular for laser coupling). All coatings are UHV compatible and comply
with the ratings of the particular view port.
The window in each view port assembly is mounted in a metal ring, which is welded to a stainless steel ConFlat “CF” flange.
Where lead glass X-ray protection is required, the lead glass window mounts to the ConFlat flange exterior above the main
view port window. It can be removed and replaced as required.