Vacuum Viewports for High Vacuum & Ultra-High Vacuum Applications

Apex Vacuum offers vacuum viewports for applications in high vacuum and ultra-high vacuum (UHV). There are a number of viewport window options available to cover light wave frequencies required by many photonic applications. Options such as anti-reflective coatings are available upon request.

The window sizing of vacuum viewports, with provided viewable areas, are available up to 3 inches. Flanges can be weldable, ConFlat (CF) or Quick Flange (NW, KF & QF). Custom capabilities include pressure & temperature options. Vacuum viewports with different optical finishes such as surface polish, flatness, parallelism, clear aperture, wedge angle, focal length and thickness are also available.

Kodial Glass Vacuum Viewports provide exceptional mechanical durability, thermal stability, and optical clarity for demanding vacuum and instrumentation applications. Made from premium borosilicate Kodial glass, these viewports are engineered for reliable performance in harsh environments where strength, chemical resistance, and precise optical transmission are critical. Kodial glass viewports are manufactured from 304 stainless steel and alkali borosilicate 7056. Kodial glass allows for the operator to view a process, make measurements of emissions, and initiate chemical action from a specific wavelength. Usable to temperatures of 200°C.

Fused Silica Viewports are available with diameters up to 8 inches and include zero length designs for low profile applications. These are all bakeable to 200˚C. Several standard grades of Fused Silica windows are offered and have excellent transmission from 193nm to 2 microns. Manufactured from high-grade fused silica with very low hydroxyl content, these windows offer excellent transmission from 180 nm through the visible spectrum—ideal for UV lasers, fluorescence systems, plasma diagnostics, and photonics research.

Deep (DUV) Fused Silica Viewports are available with diameters up to 8 inches and include zero length designs for low profile applications. These are all bakeable to 200˚C. Several standard grades of Fused Silica windows are offered and have excellent transmission from 193nm to 2 microns. Constructed from high-purity fused silica with extremely low defect density, these windows provide superior throughput at wavelengths from 180–300 nm—ideal for DUV lithography, Raman spectroscopy, excimer lasers (193 nm, 248 nm), and plasma diagnostics.

Typical Specifications

Material: Optical-grade Magnesium Fluoride (MgF₂)
Clear aperture: 10 mm – 150+ mm standard; custom sizes on request
Thickness: 1.5 – 12 mm depending on aperture and pressure differential
Flatness: λ/4 @ 632.8 nm standard (λ/10 or λ/20 optional)
Surface quality: 40/20 scratch/dig typical
Transmission:
- ~90%+ from ~150 nm–6 µm (uncoated)
- Enhanced UV performance with single- or multilayer AR coatings
Vacuum rating: HV and UHV options available to 10⁻⁹ Torr (mount-dependent)

Typical Specifications

Material: Optical-grade Germanium (Ge)
Clear aperture: 10–150 mm (larger on request)
Thickness: 1–10+ mm depending on aperture and pressure differential
Refractive index: ~4.0 at 10 µm
Transmission range: 2–14 µm
Surface quality: 40/20 or better
Flatness: λ/4 @ 632.8 nm (higher precision optional)
Seal options:
- Indium (UHV & reworkable)
- Brazed (permanent UHV)
- O-ring (general vacuum)
Vacuum rating: Down to 10⁻⁹ Torr dependent on mounting design

BBAR Coated Viewports come with view diameters of up to 2.69 inches. Viewports are made from a BBAR Coated HPFS 7980 Fused Silica material. Viewports or vacuum windows can be specified with either 2.75” CF or 4.5 CF flanges. BBAR Fused Silica Vacuum Viewports deliver exceptional optical clarity, broadband transmission, and ultra-low reflection across UV, visible, and NIR wavelengths. Engineered from high-purity fused silica and coated with a precision BBAR (Broadband Anti-Reflection) coating, these viewports provide superior performance for laser systems, imaging, spectroscopy, and high-vacuum environments.

Typical Specifications

Material: High-purity fused silica (UV-grade or IR-grade available)
Transmission range:
- UV-grade: 180 nm – 2.4 µm
- IR-grade: 250 nm – 3.5 µm
Visible transmission: >92–95% (uncoated), >99% with BBAR
BBAR coating:
- Broadband AR (UV-VIS-NIR or VIS-NIR)
- <0.5% reflection per surface (typical)
- High-power and laser-resistant options
Refractive index (at 587.6 nm): ~1.458
Surface flatness: λ/4 – λ/10 available
Surface quality: 20-10 / 40-20 depending on model
Wavefront distortion: <λ/10 typical

Typical Specifications

Viewport Type: Differentially pumped multi-stage optical viewport
Pressure Handling: Supports large ΔP through staged reduction
Stages Available:
- Single differential stage
- Dual-stage (most common for UHV)
- Multi-stage options for extreme gradients
Typical Pressure Gradient: Up to atmosphere → HV/UHV (dependent on window material & design)
Window Materials:
- Fused silica
- Sapphire
- ZnSe / ZnS
- CaF₂ / MgF₂
- BK7 / Kodial / Quartz
- Custom materials available

Titanium is the preferred choice where stainless steel falls short. Its non-magnetic, high-strength, and corrosion-resistant properties make it ideal for systems requiring performance under extreme chemical or thermal conditions. For advanced optical access under vacuum, titanium viewports provide unmatched reliability and longevity.

Our non-magnetic viewport selection includes those manufactured with non-magnetic Stainless Steel or All-Titanium. All connections to the vacuum system are ConFlat for the best seal. Choices range from 200˚C to 450˚C for bakeout temperatures, depending on glass type and coating (Sapphire or Fused Silica).

Titanium vacuum viewports are ideal for:

Semiconductor etch and deposition systems
Space simulation chambers
Plasma research and fusion devices
Aerospace propulsion test systems
Laser optics under vacuum
High-energy physics and UHV instrumentation
Corrosive or halogen-rich vacuum environments

Our Re-Entrant Vacuum Viewports provide a unique extended “tube-in” geometry that allows optical instruments, sensors, probes, and laser diagnostics to be positioned closer to the process environment without breaking vacuum. Designed for high-vacuum and ultra-high-vacuum (UHV) applications, these viewports deliver superior optical clarity, reduced standoff distance, and increased measurement accuracy.

Re-entrant designs are essential in systems requiring tight alignment, near-field imaging, high-intensity laser delivery, and precise internal visualization—all while maintaining full vacuum integrity.

Re-entrant Viewports come with view diameters of up to 2.7 inches, and are bakeable to 200˚C. All flange types are ConFlat, and all glass is made from fused silica. The stainless steel re-entrant tube is customizable in length for individual system needs.

Applications

Plasma diagnostics and spectroscopy
Near-field optical imaging
High-intensity laser delivery and alignment
In-situ process monitoring
Microscopy and interferometry under vacuum
Beamline instrumentation
Semiconductor etch/deposition tools
Experimental physics and fusion research

Vacuum Viewports