Eliminate unwanted reflections at the surface level with ultra thin, vacuum deposited low reflectance coatings engineered for broadband optical absorption.

Acktar provides fully inorganic, ultra black coatings applied directly to precision components or supplied as coated foils and films. With thickness typically <5 µm, coatings are selectively masked and engineered to achieve extremely low total hemispherical and specular reflectance from EUV and UV through VIS, NIR, MWIR, and into FIR.

Surface reflectance directly determines stray light behavior inside an optical system. When reflectance is not aggressively suppressed, ghosting, background noise, and signal degradation become unavoidable performance limitations.

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What Problem Does This Solve?

In optical and electro optical systems, uncontrolled surface reflections degrade performance. Even minimal residual reflectance from mechanical structures, housings, apertures, mounts, and internal cavities introduces measurable optical error.

Low reflectance coatings are required wherever surface reflections must be minimized to preserve optical integrity.

Excess reflection leads to:

  • Reduced image contrast and dynamic range
  • Elevated detector background signal
  • Ghosting and flare
  • Measurement uncertainty in spectroscopy and metrology
  • Reduced signal to noise ratio
  • Multi path internal reflections
  • Unwanted thermal loading of detectors

Critical in:

  • Broadband systems (UV–IR)
  • High dynamic range imaging
  • Low signal detection systems
  • Grazing angle geometries
  • Compact optical layouts
  • Cryogenic, vacuum, or space environments

Mechanical baffling blocks light paths.
It does not eliminate reflective surfaces.
Reflection must be engineered at the material interface.

 

Low Reflectance vs. Anti-Reflective (AR) Coatings

These technologies are often confused because both reduce reflection. They serve opposite optical purposes.

AR Coatings Low Reflectance Coatings
Applied to lenses and transmissive optics Applied to mechanical and structural components
Increase transmission Maximize absorption
Reduce interface reflection Minimize total hemispherical reflectance
Allow light to pass Eliminate unwanted light

AR coatings maximize useful signal throughput.
Low reflectance coatings suppress unwanted photons.
They are complementary technologies – not interchangeable.

Acktar’s Approach to Low Reflectance

Acktar coatings are produced using proprietary vacuum deposition processes that form controlled nano and micro scale surface morphology.

The coatings are fully inorganic and ultra-thin (<5 µm), preserving sharp edges, fine geometries, apertures, and dimensional tolerances without buildup.

Key Characteristics

  • Extremely low total hemispherical reflectance
  • Near-zero specular reflectance
  • Diffusive ultra black absorption
  • Broadband performance from EUV to FIR (product dependent)
  • Stable optical properties across temperature extremes
  • No cracking, flaking, or aging under thermal cycling
  • Fully inorganic – no volatile constituents
  • Qualified for vacuum, cryogenic, and space environments

Low reflectance is engineered where reflection originates – at the surface.

Implementation Approaches

Acktar supports two complementary integration paths.

1. Direct Coating on Precision Components

Selective masking enables coating only optically relevant areas while preserving mechanical interfaces and tolerances.

Coating Family Typical Spectral Range Optical Behavior Typical Applications Environmental Capability
Magic Black™ EUV – UV – VIS Extreme absorption EUV optics, UV instruments Vacuum, cryogenic, space
Vacuum Black™ EUV – NIR Ultra-low reflectance Optical baffles, metrology tools Vacuum, thermal cycling
Fractal Black™ VIS – IR (to FIR) Diffusive ultra-black absorption Imaging systems, spectrometers Cryogenic to high temperature
Core Black™ EUV – NIR Ultra-flat, particle-free diffusive Wafer chucks, precision mounts Vacuum, ESD-safe, ultra-clean

Direct coating is preferred when:

  • Dimensional tolerances are critical
  • Geometry is complex
  • Maximum durability is required
  • Masking of functional surfaces is needed

 

2. Coated Foils, Films, and Sheets

Pre coated materials for integration when direct coating is impractical or modular design is preferred.

Implementation Approaches

Acktar supports two complementary integration paths.

1. Direct Coating on Precision Components

Selective masking enables coating only optically relevant areas while preserving mechanical interfaces and tolerances.

Product Form Factor Spectral Range Optical Behavior Typical Applications
Hexa-Black™ Absorbing sheets / panels UV – MWIR Lowest reflectance at grazing angles Grazing-angle baffles
Metal Velvet™ Coated aluminum foil UV – IR Highly diffusive absorption Light traps, housings
Fractal Black™ on Polyimide Flexible film UV – MWIR Diffusive, lightweight Space payloads
Fractal Black™ on Copper Flexible copper foil VIS – IR Absorption + thermal conductivity Opto-thermal assemblies

 

Foils and films are ideal for:

  • Retrofitting existing systems
  • Large-area lining
  • Lightweight integration
  • Flexible or patterned components

 

Technical Performance

  • Spectral Coverage: EUV/UV through VIS, NIR, MWIR, FIR (coating dependent)
  • Total Hemispherical Reflectance: typically <1.3%, reaching <1% at selected wavelengths
  • Solar Absorptivity (300–2500 nm): ~0.98
  • Emissivity (1.5–21 µm measured): ~0.88–0.90
  • Specular Reflectance: near-zero
  • Angular Performance: stable absorption at normal and grazing incidence
  • Coating Thickness: typically <5 µm
  • Thickness Tolerance: tight tolerances achievable upon request, down to ±0.4 µm
  • Knife Edge Conformality: maintains sharp geometries, radius <7 µm
  • Uniformity: SEM-verified thickness uniformity across complex geometries and undercut features
  • Adhesion: ASTM D3359 5A rating (no coating removal)
  • Thermal Shock Resistance: validated from elevated temperature (~125°C) to cryogenic exposure (liquid nitrogen) without flaking or cracking
  • Zero Auto Fluorescence: no measurable fluorescence under UV excitation, preventing background signal contamination in sensitive optical and semiconductor systems
  • Extremely Low Molecular Contamination: MOC <10⁻⁹ g/cm²
  • Mechanical Stability: high vibration stability
  • Cleanability: resistant to IPA, ethanol, acetone, ultrasonic solvent cleaning, and argon plasma cleaning with negligible change in thermo-optical performance

Performance validated through thermal cycling, thermal vacuum testing, cryogenic exposure, adhesion testing, reflectance stability after environmental stress, and space-environment simulation.

 

Structural Bonding Capability

Beyond stray light suppression, Fractal Black™ has demonstrated performance as a structural bonding primer.

  • Lap Shear Strength (EC-2216 adhesive): ~3.4–3.9 ksi, comparable to industry standard aerospace primers
  • Cohesive dominant failure modes observed, indicating reliable bond integrity
  • Enables dual-function use: stray light control + structural primer on the same surface

This dual capability reduces processing steps, eliminates separate primer application, and simplifies fabrication of complex opto-mechanical assemblies.

 

Applications

  • Internal optical baffles and light traps
  • Precision apertures, pinholes, diaphragms
  • Imaging systems and cameras
  • Telescopes and scientific instruments
  • Laser beam dumps and absorbers
  • Semiconductor process equipment, wafer inspection systems, precision metrology platforms, and advanced lithography tools
  • Cryogenic optical and thermo optical assemblies
  • Spaceborne optical payloads

 

Integration & Compatibility

  • Substrates: compatible with virtually all engineering materials including aluminum, copper, stainless steel, titanium, tungsten, molybdenum, magnesium, Invar, Kovar, nickel, silicon, sapphire, ceramics, glass, and high-performance polymers such as PEEK, Ultem (PEI), polyimide, ABS, and related engineering thermoplastics (application dependent)
  • Formats: direct coating, foils, films, sheets, rolls, die-cuts, patterned components
  • Geometries: complex 3D parts, fine apertures, sharp edges, thin baffle vanes
  • Precision Masking: due to the ultra thin (<5 µm) conformal nature of the coating, masking is typically unnecessary for most mechanical interfaces. When explicitly required, coating can be selectively applied only to optically active regions while leaving sealing surfaces, bonding areas, electrical contacts, and grounding points completely uncoated—preserving assembly integrity without secondary machining.
  • Patternability: compatible with conventional photolithography, etching, and lift off processes
  • Electrical Properties: tailorable electrical conductivity; available in dissipative range for ESD-sensitive systems
  • Cleanroom Compatibility: handling and packaging available from ISO 8 to ISO 5 upon request.
  • Manufacturing Routes: customer-furnished parts, coating of patterned sheets, turnkey manufacturing
  • Vacuum / UHV: suitable for high vacuum, ultra-high vacuum (to 10⁻¹¹ mbar), thermal vacuum, and space systems
  • Toxicity Free Composition: fully inorganic, RoHS and REACH compliant, free of volatile binders and hazardous organic compounds; suitable for sensitive environments where material purity and non toxicity are critical

 

Mission-Proven Results

Acktar low reflectance coatings are deployed in operational systems across space, semiconductor, metrology, laser, and scientific instrumentation markets.

Delivered benefits include:

  • Measurable contrast improvement
  • Reduced ghost artifacts
  • Improved signal to noise ratio
  • Stable long term optical performance

 

Related Solutions

  • Thermal Control & Emissivity Management
  • Laser Light Management
  • High Performance Optical Coatings