Synthetic Diamond Optical Elements with ICP Etched Anti-Reflective Patterns
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Solution Overview
Problem
Existing synthetic diamond optical elements with thin film anti-reflective coatings are prone to damage in high power optical systems due to high absorbance and poor thermal conductivity, leading to a low laser-induced damage threshold and mechanical integrity issues, while alternative anti-reflective surface patterns on diamond materials suffer from surface and sub-surface crystal damage.
Innovation Solution
The development of an anti-reflective surface pattern formed directly in the synthetic diamond material using inductively coupled plasma reactive ion etching (ICP RIE) with optimized gas flows, pressures, and power settings to create low absorbance and low reflectance surfaces with minimal crystal damage, achieving a high laser-induced damage threshold and improved optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If thin film anti-reflective coatings are applied to synthetic diamond optical elements, then reflectance is minimized, but the coating is prone to damage in high power optical systems due to high absorbance and poor thermal conductivity
Solution Approach 1:
The patent removes the thin film anti-reflective coating from the synthetic diamond optical element, extracting the problematic layer that causes damage while maintaining the bulk diamond material's properties. The solution relies on the inherent low reflectance of the diamond material itself rather than relying on a separate coating layer.
Solution Approach 2:
The patent eliminates the thin film coating that is prone to damage and replacement, opting instead for a permanent solution using the bulk diamond material's inherent optical properties. This avoids the need for fragile, replaceable coating layers.
2Reliability
If anti-reflective surface patterns are formed directly in diamond material, then coating damage is avoided, but surface and sub-surface crystal damage is introduced reducing laser induced damage threshold
Solution Approach 1:
The patent changes the processing parameters and methodology to form anti-reflective surface patterns without introducing crystal damage. By optimizing the fabrication process parameters, the solution achieves the desired surface structure while maintaining the bulk crystal integrity and avoiding sub-surface damage.
Solution Approach 2:
The patent replaces mechanical processing methods that cause crystal damage with alternative fabrication techniques. Instead of using mechanical grinding or traditional machining, the solution employs processes that create the anti-reflective structure without mechanical stress or crystal lattice damage.
3Ease of manufacture
If traditional processing methods are used to form anti-reflective surface structures in diamond, then surface patterns can be created, but significant surface and sub-surface crystal damage is incorporated into the material
Solution Approach 1:
The patent replaces traditional mechanical processing methods with alternative fabrication techniques that do not cause crystal damage. The solution uses processes such as chemical vapor deposition or other non-mechanical methods to create surface patterns while preserving the diamond crystal structure.
Solution Approach 2:
The patent modifies the fabrication process parameters to eliminate harmful effects. By changing the processing conditions, temperature, pressure, or chemical environment, the solution achieves surface pattern formation without introducing crystal damage or sub-surface defects.
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 solution results in synthetic diamond optical elements with low absorbance, low reflectance, and high laser-induced damage thresholds, minimizing beam aberrations and maintaining optical performance under extreme power densities, while being cost-effective and scalable.
Implementation Method 1
inductively coupled plasma reactive ion etching (ICP RIE)
Implementation Method 2
inductively coupled plasma reactive ion etching (ICP RIE)
Data Source
Figure 1~2
AI summary
An optical element 10 is made of synthetic diamond material and has an anti-reflective surface pattern 16 formed directly in at least one surface. The optical element has an absorption coefficient measured at room temperature of ≤ 0.5 cm-1 at a wavelength of 10.6 µm. It has a reflectance at said at least one surface of no more than 2% at an operating wavelength of the optical element. It has a laser induced damage threshold which is at least 30 Jcm-2 measured using a pulsed laser at a wavelength of 10.6 µm with a pulse duration of 100 ns and a pulse repetition frequency in a range 1 to 10 Hz and/or is at least 1 MW/cm2 measured using a continuous wave laser at a wavelength of 10.6 µm. The surface pattern may be formed by an inductively coupled plasma (ICP) etching process which minimises nitrogen-vacancy (NV) defects in single crystal chemical vapour deposition (CVD) diamond materials.