ABSTRACT
Many optical systems require windows to protect the system from dust and debris. Low-temperature cryostats and ultra-high vacuum thin film deposition systems, such as molecular beam epitaxy (MBE), require windows to keep the environment in the system separated from the surrounding environment. MBE windows are made of glass sealed onto stainless steel conflate flanges with a vacuum integrity of 5-10 × 10-11 torr. The design of a window involves several factors such as strength, transmission range, environmental durability, and availability of anti-reflections coatings. There are three grades of synthetic fused silica: optical quality, Ultraviolet (UV), and infrared (IR). The UV grade has high transmittance starting at 180 nm whereas the optical quality has high transmittance starting at 260 nm. UV grade fused silica has a strong OH-absorption band in the wavelength range 2600-2800 nm. However, the absorption band is absent in the IR grade fused silica.
