This is a fused quartz replacement window for the Ideal Vacuum Cube 6x6 Viewing Window AssembIy. Use it to replace or upgrade a scratched, hazed or discolored glass window. It replaces the viewing window pane used on our 6x6x6 or 6x6x12 Cubes.

Our fused quartz windows are manufactured with the highest quality natural quartz resulting in the highest levels of purity and lowest inclusion and bubble levels. Comparable to Heraeus TSC-3, these windows have improved transmittance, and a wider useful wavelength range than standard glass. Characteristics include low refractive index variations and low thermal expansion coefficient. Fused quartz is used for semiconductor applications such as plasma etch and deposition systems and recommended when low alkali and low aluminum content are specified. It is often used for transmissive optics in the visible and near-to-mid infrared wavelengths where a high laser damage threshold is required. Fused quartz has absorbtion bands in the 2600 to 2900 nm region, similar to fused silica but not as strong. It is unsuitable for UV work due to absorbtion in the 270 nm region.

Note that fused quartz stock is limited as Ideal Vacuum is transitioning to fused silica as its premium window offering. Also note that fused quartz windows may be erroneously labeled with fused silica part numbers. You may verify your window material by checking your sales invoice.

We also offer replacement Cube window panes with standard low-iron tempered glass or fused silica. Tempered glass is commonly used for general, direct observation of roughing or high-vacuum chamber processes and can be used to facilitate optical alignments of chamber components, observe degassing of fluids, or used to help teach in-vacuo processes by direct observation. The glass material is standard low-iron float glass. Surface quality and flatness is Q4 per ASTM 1036-06 and 1048-04. The low iron content of the glass results in it having a slight blueish tint. This economical glass is unsuitable for laser experiments below visible or beyond near-infrared (NIR) wavelengths.

Our high purity fused silica replacement windows are ground and polished to optical grade on both sides with a total thickness variation (TTV) of <10µm, a surface finish of S/D 40/20, and a surface roughness of Ra < 1 nm. These windows have appreciably improved transmittance, and a wider useful wavelength range than standard glass. Characteristics include extraordinarily low refractive index variations, low birefringence values, and an ultra-low thermal expansion coefficient. Fused silica is used for transmissive optics where a high laser damage threshold is required. Fused silica is used for optics operating in the deep UV, visible, and the near infrared wavelength range.


Newer versions of the viewing window assembly are field upgradeable. Please download the IVP Cube Viewing Window Assembly Manual for instructions.

If you have an older viewing window plate assembly (does not have a bare aluminum window frame), we will upgrade the entire viewing window assembly at no charge to our latest version when you order a replacement window. The latest version includes thicker glass and is more leak resistant. When you purchase the new replacement window, just let us know (by phone or email) that you have an older model. We will provide an RMA and return shipping label for you to send us your old viewing window plate assembly. Once we receive the old plate assembly, we will send you a complete, fully tested, updated assembly. Old plate assemblies will not be returned.

NOTE: All viewing windows or viewports are inherently fragile, should be handled carefully, and always inspected before use. Ideal Vacuum viewing windows are designed and rated for VACUUM ONLY and can be susceptible to thermal shock if exposed to rapid temperature changes (>10° C /min). If directing a laser beam through the window, make sure the laser’s wavelength can be reasonably transmitted through the window’s material. Please download and read all the safety warnings in the IVP Cube Viewing Window Assembly Manual.