DIASEMI Pre-AR Coated CVD Diamond Window Dies for the Photonics Industry

Enabling the Next Generation of Miniaturized Optical Systems

As photonics systems continue to scale toward higher power densities, smaller footprints, and harsher operating environments, the demand for advanced optical window materials has intensified. Applications in optical communications, high-power lasers, and sensing technologies require materials that simultaneously deliver:

• High optical transmission
• Exceptional thermal conductivity
• Mechanical robustness
• Long-term environmental stability

Conventional optical materials—such as fused silica or sapphire—often fail to meet all these requirements simultaneously. This limitation has driven increasing interest in CVD diamond, a material uniquely positioned at the intersection of optics, thermal management, and extreme durability.

DIASEMI introduces a breakthrough solution:

Pre-AR Coated CVD Diamond Window Dies

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A Fundamental Shift in Optical Coating Architecture

Traditional approaches rely on depositing anti-reflective (AR) coatings after the diamond substrate has been fabricated and polished. While effective for large optics, this method becomes impractical for micro-scale window dies (sub-millimeter dimensions), where handling, alignment, and coating uniformity present major challenges.

DIASEMI’s innovation reverses this paradigm.

Instead of post-processing, we implement a pre-deposition architecture, where the optical coating is engineered before diamond growth. This approach integrates thin-film optics directly into the material synthesis process, leveraging principles of thin film interference at the earliest stage of fabrication.

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Technology Overview

1. Pre-Engineered Optical Coating Layer

A precisely designed anti-reflective coating is deposited onto a sacrificial substrate using advanced thin-film deposition techniques (PVD or CVD). Material systems are selected based on wavelength requirements:

• SWIR (0.8–1.5 µm): SiO₂, Si₃N₄
• MWIR / LWIR: Y₂O₃, HfO₂, ZrO₂, rare-earth oxides

Layer thickness is optimized according to optical interference conditions to minimize surface reflection.

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2. Direct CVD Diamond Growth

High-quality diamond is then grown directly on the AR-coated surface using chemical vapor deposition (CVD). During this process:

• Diamond inherits the optical interface
• The AR coating undergoes in-situ thermal stabilization (~800–900°C)
• A robust, low-defect interface is formed

This step also ensures compatibility with high-power photonic environments.

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3. Precision Microfabrication

Following growth, the diamond surface is:

• Mechanically polished to optical grade (Ra ≤ 10 nm)
• Laser diced into micro-scale dies (down to <500 µm)
• Plasma treated to remove graphitic residues

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4. Sacrificial Substrate Removal

The original substrate is selectively removed via chemical or plasma etching, leaving behind a self-supported diamond window with an integrated AR coating.

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Key Advantages

Native Integration of Optical Functionality

The AR coating is not an add-on—it is structurally integrated into the diamond window. This eliminates interface weaknesses associated with post-deposition coatings.

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Wafer-Level Manufacturing of Micro Windows

DIASEMI’s process enables batch fabrication of ultra-small optical dies, overcoming the limitations of conventional coating techniques.

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Superior Thermal and Mechanical Stability

Because the coating is exposed to the full CVD growth environment, it achieves:

• High thermal stability
• Strong adhesion
• Reduced residual stress

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Enhanced Optical Performance

Optimized AR coatings significantly reduce Fresnel reflection at the diamond interface, improving transmission efficiency across target wavelengths.

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Reduced Processing Complexity and Cost

By eliminating post-growth coating steps, the process:

• Simplifies manufacturing flow
• Improves yield
• Enables scalable production

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Performance Characteristics

Typical DIASEMI Pre-AR Diamond Window Dies offer:

• Transmission: >98% (design-dependent)
• Surface roughness: ≤ 10 nm
• Thickness: 5–50 µm
• Die size: down to 0.3–0.5 mm
• Thermal conductivity: up to 2000 W/m·K (diamond bulk)

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Application Areas

DIASEMI’s pre-AR coated diamond windows are engineered for demanding photonics applications, including:

• Optical communication modules (SWIR band ~1.0–1.5 µm)
• High-power laser systems (e.g., ~1 µm wavelength platforms)
• Infrared sensing and imaging systems
• Harsh-environment optical sensors
• MEMS and micro-photonic packaging