Diamond Multilayer Antireflective Coating for Infrared Windows
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Solution Overview
Problem
Existing antireflective coatings for optical windows, particularly in the medium wavelength infrared range, face issues with delamination, degradation, and fluctuating optical transmissivity, limiting the use of diamond-based semiconductor devices due to diamond's sharp absorption spectra and high fabrication costs.
Innovation Solution
A diamond-based multilayer antireflective coating system is developed, comprising alternating layers of polycrystalline diamond, germanium, and fused silica films on an optical grade silicon substrate, optimized using optical design software to achieve near-zero reflectance across specific infrared wavelengths, enhancing transmissivity and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If diamond-based antireflective coatings are used, then transmissivity is improved, but delamination and degradation occur
Solution Approach 1:
The patent applies composite materials by creating a multilayer structure combining diamond films with germanium and fused silica layers. This composite approach allows the system to achieve the high transmissivity of diamond while the germanium and fused silica layers provide mechanical stability and prevent delamination, thus resolving the contradiction between improved transmissivity and reduced reliability.
Solution Approach 2:
The patent segments the single diamond coating into multiple thin layers alternating with germanium and fused silica layers. This segmentation creates a gradient structure that reduces stress concentration and prevents delamination, while maintaining the optical transmissivity benefits of diamond across the infrared spectrum.
2Illumination intensity
If diamond-based coatings are applied, then optical transmissivity is enhanced, but fabrication cost increases
Solution Approach 1:
The patent applies local quality by using diamond material only where optically critical (in alternating thin layers) rather than coating the entire substrate with thick diamond. The germanium and fused silica layers are used in regions where mechanical stability is more important, optimizing the balance between optical performance and fabrication cost.
Solution Approach 2:
The patent changes the parameter of diamond layer thickness to very thin films (alternating with other materials), which reduces the amount of expensive diamond material required while maintaining optical benefits. This parameter optimization makes the fabrication process more economically viable.
3Illumination intensity
If diamond layers are deposited, then transmissivity improves, but reflectance fluctuates
Solution Approach 1:
The patent creates a dynamic multilayer structure where the optical properties emerge from the interaction between multiple layers with different refractive indices. The alternating diamond-germanium-fused silica configuration dynamically manages light reflection and transmission across different wavelengths, stabilizing overall transmissivity despite variations in individual layer properties.
Solution Approach 2:
The composite multilayer structure compensates for the sharp absorption spectra of diamond by incorporating germanium and fused silica layers with complementary optical properties. This composite approach smooths out reflectance fluctuations across the infrared spectrum, maintaining stable transmissivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The multilayer coating system provides high transmissivity and durability, overcoming previous limitations by incorporating diamond's advantageous properties while minimizing reflectance and maintaining performance across a wide infrared spectrum, suitable for applications like battlefield optics.
Implementation Method 1
A multilayer film synthesis provides nanocrystalline diamond based antireflective coatings fabrication which is beneficial for use in medium wavelength infrared applications
Implementation Method 2
Nanocrystalline diamond may provide high transmissivity infrared windows with high reliability
Data Source
AI summary
A system and method for diamond based multilayer antireflective coating for optical windows are provided. An antireflective coatings for optical windows may include an optical grade silicon substrate; a plurality of polycrystalline diamond films, a plurality of germanium films, and a plurality of fused silica films. A method of fabricating a diamond based multilayer antireflective coating may include the steps of cleaning and seeding an optical substrate, forming a plurality of diamond layers above the optical substrate, forming a plurality of germanium layers above the optical substrate; and forming a plurality of fused silica layers above the optical substrate, wherein the reflectance of the antireflective coating is between 0.1 and 3.0 percent for infrared spectrum wavelengths between 1800 and 5000 nanometers.