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Vacuum Viewports

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High Vacuum Viewports
Ultra-High Vacuum Viewports

Fused Silica – Glass – Sapphire – Magnesium Fluoride – Calcium Fuoride – Zinc Selenide – BBAR Coated Fused Silica – Corning HPFS Fused Silica – UV Fused Silica – EUV Fused Silica (Excimer Grade)

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.

Typical Specifications

  • Material: Kodial borosilicate glass

  • Refractive index (at 587.6 nm): ~1.472

  • Abbe number: ~64

  • Transmission range: 320 nm – 2.5 µm

  • Visible transmission: >90% (uncoated)

  • Optical surface quality: 40-20 or better (per application)

  • Available coatings:

    • Visible AR

    • NIR AR

    • Broadband AR

    • Protective & hydrophobic coatings

Kodial Glass

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.

Applications

  • Laboratory vacuum chambers

  • Industrial process equipment

  • Analytical instrumentation

  • Semiconductor and microfabrication systems

  • Optical inspection ports

  • Environmental and materials testing chambers

  • Research & development vacuum assemblies

Typical Specifications

  • Material: High-purity UV-grade fused silica

  • Transmission Range: 180–2000 nm (UV-optimized)

  • Vacuum Rating: High vacuum / UHV

  • Surface Quality: 10-5 scratch/dig (typ.)

  • Flatness: λ/10 @ 632.8 nm (typ.)

  • Optional Coatings: Narrowband UV AR, broadband UV-VIS AR, custom wavelength treatments

  • Flange Options: CF (ConFlat), ISO-K / ISO-F, KF, custom assemblies

UV Fused Silica

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.

Applications

  • UV & Deep-UV Laser Delivery

  • Semiconductor Inspection & Lithography

  • UV Spectroscopy & Metrology

  • Fluorescence and Photochemistry Systems

  • High-Vacuum Research & Instrumentation

  • Beam Diagnostics & Monitoring

Typical Specifications

  • Material: High-purity UV/DUV-grade fused silica
  • Wavelength Range: 180–2000 nm (optimized for 180–300 nm DUV)
  • Vacuum Rating: High vacuum / UHV
  • Surface Quality: 10-5 scratch/dig (typ.)
  • Flatness: λ/10 @ 632.8 nm (typ.)
  • Coatings: DUV AR, excimer laser AR (193 nm, 248 nm), or custom
  • Flange Types: CF (ConFlat), ISO-K / ISO-F, KF, or custom assemblies

DUV Fused Silica

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.

Applications

  • DUV Laser Delivery Systems (e.g., 193 nm, 248 nm excimer lines)
  • Semiconductor Lithography & Inspection Tools
  • Plasma Diagnostics & DUV Spectroscopy
  • UV Photonics Research & Metrology
  • High-Vacuum Optical Chambers
  • Beam Profiling, Monitoring & Alignment

Typical Specifications

  • Material: Ultra-high-purity fused silica
  • Wavelength Range: EUV to UV-VIS (optimized for 13.5 nm EUV and deep-UV)
  • Vacuum Rating: High vacuum / Ultra-High Vacuum (UHV)
  • Surface Quality: 10-5 scratch/dig (typ.)
  • Flatness: λ/10 @ 632.8 nm (typ.)
  • Flange Options: CF (ConFlat), ISO-K / ISO-F, KF, custom configurations

Eximer (EUV) 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. Made from ultra-high-purity fused silica, these windows support applications involving EUV (including 13.5 nm wavelength systems) while maintaining extremely low absorption and minimal beam distortion.

Applications

EUV Fused Silica

  • EUV Lithography and Semiconductor Manufacturing
  • EUV Metrology, Inspection, and Beam Delivery
  • Plasma Science & High-Vacuum Research
  • Extreme Ultraviolet Spectroscopy and Diagnostics
  • High-Intensity Laser Systems
  • EUV Beam Profiling, Monitoring & Alignment

Typical Specifications

  • Optic Material: Single-crystal sapphire
  • Transmission Range: ~200–5000 nm (UV to IR)
  • Vacuum Rating: High vacuum / Ultra-high vacuum
  • Surface Quality: 10-5 or 20-10 scratch/dig (application-dependent)
  • Flatness: λ/10 @ 632.8 nm (typ.)
  • Coatings: UV AR coatings, broadband AR, or custom designs
  • Flange Options: CF (ConFlat), ISO-K / ISO-F, KF, and custom assemblies

UV Sapphire

UV Sapphire viewports come with view diameters up to 3 inches, and are bakeable to 450˚C. Single crystal, sapphire windows come with orientation either 0˚ or 90˚ and provide transmission from 250nm to 4 microns.   Single-crystal sapphire provides excellent transmission from 200 nm into the infrared, making it ideal for UV imaging, UV laser delivery, fluorescence systems, and plasma diagnostics.

Applications

  • UV Laser Delivery & Beam Transport
  • Plasma Chambers & High-Temperature Vacuum Systems
  • UV Spectroscopy & Metrology
  • Semiconductor Processing & Inspection Equipment
  • Harsh Environment Optical Monitoring
  • High-Pressure / High-Temperature Viewing Windows

Laser Optics

Laser Optics Fused Silica Viewports pair a specific type of Fused Silica with a precise AR V-Coating specific to your laser wavelength. These viewports are bakeable to 200˚C. We have four standard wavelengths: 193nm, 248nm, 780nm, and 1064nm. If you need a wavelength, please contact Apex Vacuum and we will assist you to get the best performing viewport for your application.

Typical Specifications

  • Transmission range: 180–5000 nm
  • Optimized DUV performance: 180–300 nm
  • Refractive index: 1.76 at 193 nm
  • Surface quality: 10–5 to 40–20 scratch-dig (options available)
  • Surface flatness: λ/10 to λ/2 @ 633 nm (depending on size)
  • AR coatings available for improved transmission

DUV Sapphire

DUV Sapphire viewports come with view diameters up to 3 inches, and are bakeable to 450˚C. Single crystal, sapphire windows come with orientation either 0˚ or 90˚ and provide transmission from 250nm to 4 microns. Excellent transmission in the DUV range (180–300 nm), making it perfect for semiconductor lithography and other UV-related applications.

Applications

  • Deep-ultraviolet lithography (DUV)
  • Semiconductor inspection and wafer processing
  • Plasma etching and plasma monitoring windows
  • Laser delivery & UV spectroscopy systems
  • Synchrotron beamlines & high-energy research
  • UV curing systems & photonics instrumentation

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

BBAR Coated

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.

Applications

  • UV–NIR laser systems
  • High-precision optical diagnostics
  • Vacuum chamber observation and imaging
  • Spectroscopy and interferometry
  • Semiconductor and metrology equipment
  • Scientific research and R&D facilities
  • Materials processing and environmental testing

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

Differentially Pumped

Differentially Pumped Vacuum Viewports are engineered to maintain optical access between regions of significantly different pressures, enabling stable operation in demanding environments where a standard viewport cannot safely withstand the full pressure differential. This advanced design incorporates one or more intermediate pumped stages, allowing safe pressure reduction, improved system longevity, and protection for sensitive optical windows.

Applications

  • Beamline and accelerator facilities
  • High-power laser beam delivery
  • Spectroscopy & interferometry
  • Plasma diagnostics and monitoring
  • Semiconductor and materials processing
  • Gas-inlet/isolation chambers
  • Environmental & durability testing chambers
  • R&D vacuum instrumentation

Non-Magnetic

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).

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

Re-Entrant

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

Over-Pressure

Over-pressure protected UHV viewports are tested at 150% of the rated pressure. The maximum overpressure protection offered is 200 psi for ConFlat viewports. Sapphire window viewports are designed with more than 10x safety factor and are tested for up to 300 psi.

Typical Specifications

  • Transmission range: 180–5000 nm
  • Optimized DUV performance: 180–300 nm
  • Refractive index: 1.76 at 193 nm
  • Surface quality: 10–5 to 40–20 scratch-dig (options available)
  • Surface flatness: λ/10 to λ/2 @ 633 nm (depending on size)
  • AR coatings available for improved transmission

DUV Sapphire

DUV Sapphire viewports come with view diameters up to 3 inches, and are bakeable to 450˚C. Single crystal, sapphire windows come with orientation either 0˚ or 90˚ and provide transmission from 250nm to 4 microns. Excellent transmission in the DUV range (180–300 nm), making it perfect for semiconductor lithography and other UV-related applications.

Applications

  • Deep-ultraviolet lithography (DUV)
  • Semiconductor inspection and wafer processing
  • Plasma etching and plasma monitoring windows
  • Laser delivery & UV spectroscopy systems
  • Synchrotron beamlines & high-energy research
  • UV curing systems & photonics instrumentation

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