Vacuum Viewports
Vacuum viewports are specialized windows or ports integrated into vacuum systems, allowing visual observation or the transmission of light into or out of a vacuum chamber without compromising the vacuum environment. Firebird Optics offers viewports made from glass, fused silica, sapphire, ZnSe, CVD diamond and many more as well as a variety of flanges. All setups are designed to withstand the vacuum pressure and maintain optical clarity. They are sealed with high-quality, vacuum-compatible gaskets or welds to ensure they do not leak.
These viewports are essential in various fields, including materials science, semiconductor manufacturing, and fundamental physics research, where maintaining a controlled vacuum environment is crucial.
Calcium Fluoride (CaF2) Viewports
Calcium Fluoride (CaF2) Viewports
Firebird Optics’ Calcium Fluoride (CaF₂) viewports are designed for high-performance vacuum systems requiring exceptional optical transmission across a broad spectral range. With excellent transparency from the vacuum ultraviolet (VUV) through the visible and into the infrared, these viewports are ideal for spectroscopy, excimer lasers, and analytical instrumentation where high signal clarity is essential. Calcium Fluoride’s low refractive index, lack of birefringence, and high laser damage threshold make it well-suited for demanding optical environments, while its resistance to moisture, chemicals, and thermal stress ensures long-term reliability. Available in CF, KF, and ISO flange configurations, Firebird Optics’ CaF₂ viewports can be easily integrated into a wide range of vacuum systems and are fully customizable in size, thickness, coatings, and mounting options to meet specific application requirements.
Calcium Fluoride Viewports for Vacuum Systems: Specifications, Applications, and Flange Selection Guide
Introduction
Calcium Fluoride (CaF₂) viewports are high-performance optical windows designed for vacuum and ultra-high vacuum (UHV) environments where broad spectral transmission and optical clarity are essential. Manufactured from high-purity crystalline CaF₂, these viewports offer exceptional transmission from the vacuum ultraviolet (VUV) through the visible and into the infrared (IR), making them a preferred choice for spectroscopy, laser systems, and analytical instrumentation. Their combination of low absorption, high laser damage threshold, and chemical stability ensures reliable performance in demanding scientific and industrial applications.
Why Choose Calcium Fluoride Viewports?
Calcium fluoride is widely recognized as one of the most versatile optical materials for extended wavelength applications. Its key advantages include:
Broad Transmission Range: Typically from ~0.15 µm (VUV) to ~7–9 µm (IR), enabling multi-spectrum performance
Low Absorption: Ensures high signal transmission for precision optical measurements
High Laser Damage Threshold: Ideal for excimer and UV laser systems
Low Refractive Index: Reduces reflection losses and often eliminates the need for AR coatings
Chemical & Moisture Resistance: Stable in harsh environments and non-hygroscopic under normal conditions
These properties make CaF₂ viewports especially valuable for applications requiring high optical throughput across multiple wavelengths.
Typical Specifications of Calcium Fluoride Viewports
Firebird Optics’ calcium fluoride viewports are designed to meet the rigorous demands of vacuum and optical systems. Typical specifications include:
Material: Single-crystal Calcium Fluoride (CaF₂)
Transmission Range: ~150 nm to 7 µm (extended UV–IR coverage)
Surface Quality: 60/40 scratch-dig (optical grade standard)
Pressure Range: Atmosphere to UHV (~10⁻¹¹ mbar typical for CF designs)
Leak Rate: ≤ 1 × 10⁻¹⁰ mbar·L/s (He)
Flange Materials: Stainless steel (304L, 316L/316LN)
Operating Temperature: Up to ~150–200°C depending on sealing method
Available Coatings: Optional AR or wavelength-specific coatings
Custom sizes, thicknesses, and optical finishes are available to meet specific system requirements.
Applications of Calcium Fluoride Viewports
Spectroscopy & Analytical Systems
CaF₂ viewports are widely used in UV, VIS, and IR spectroscopy, where their broad transmission range ensures accurate and reliable measurements across multiple wavelengths.
Laser Systems
The material’s high damage threshold makes it ideal for excimer lasers and UV laser applications, where durability and transmission efficiency are critical.
Semiconductor & Lithography
Calcium fluoride plays a key role in microlithography and semiconductor processing, particularly in deep-UV systems requiring high optical purity.
Thermal Imaging & Infrared Systems
Used in thermal imaging systems and IR optics, CaF₂ provides reliable performance in both research and industrial imaging applications.
Vacuum Research & Industrial Processing
These viewports are commonly used in vacuum chambers, plasma systems, and analytical instruments, where stable optical access and vacuum integrity are essential.
Flange Options: CF vs KF vs ISO
Selecting the correct flange type is essential for ensuring proper system performance and compatibility. Calcium fluoride viewports are commonly available in CF, KF, and ISO configurations, each suited to different vacuum levels and use cases.
CF (ConFlat) Flanges – For Ultra-High Vacuum (UHV)
Seal Type: Metal-to-metal seal using copper gasket
Vacuum Range: UHV (down to ~10⁻¹¹ mbar)
Temperature Capability: Highest bake-out capability
Best Applications:
Semiconductor processing
Surface science and UHV research
Permanent vacuum installations
Why choose CF?
CF flanges provide the most reliable, leak-tight seal, making them ideal for critical UHV environments and high-temperature processes.
KF (Quick Flange) – For Flexible Systems
Seal Type: Elastomer O-ring with clamp
Vacuum Range: Rough to high vacuum
Temperature Capability: Moderate
Best Applications:
Laboratory and R&D setups
Systems requiring frequent changes or maintenance
Why choose KF?
KF flanges allow fast assembly and disassembly, making them ideal for flexible, modular systems.
ISO Flanges – For Large Vacuum Systems
Seal Type: O-ring or bolted flange
Vacuum Range: High vacuum
Temperature Capability: Moderate
Best Applications:
Large vacuum chambers
Industrial-scale vacuum systems
Why choose ISO?
ISO flanges are best suited for large-diameter systems, offering strong mechanical stability and scalability.
Custom Calcium Fluoride Viewports
Firebird Optics offers fully customizable CaF₂ viewports tailored to specific applications, including:
Custom diameters and thicknesses
Specialized coatings for UV, VIS, or IR optimization
Non-magnetic or high-purity flange materials
Integration into complex vacuum assemblies
Customization ensures optimal performance for demanding optical and vacuum environments.
