Synthetic Diamond Anti-Reflective Surface Patterns
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Solution Overview
Problem
Existing synthetic diamond optical elements face challenges with thin film anti-reflective coatings, which are prone to damage in high power optical systems due to high absorbance and poor thermal conductivity, leading to low laser-induced damage thresholds and mechanical integrity issues, while alternative anti-reflective surface patterns are difficult to process in diamond materials without introducing surface and sub-surface 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, which reduces reflectance and absorbance, and enhances the laser-induced damage threshold without introducing crystal damage, utilizing a method similar to that used in quantum sensing for forming well-defined optical structures.
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 high damage threshold properties. The solution relies on the inherent optical properties of the diamond material itself rather than relying on a separate coating layer.
Solution Approach 2:
The patent modifies the surface morphology parameters of the synthetic diamond by creating specific surface patterns (such as micro-structures or textured surfaces) that change the optical interaction with light. These parameter changes in surface geometry enable anti-reflective performance without requiring thin film coatings, thereby eliminating the coating's vulnerability to laser damage.
2Strength
If anti-reflective surface patterns are formed directly in the synthetic diamond material, then mechanical robustness is improved, but processing difficulty increases due to extreme hardness and low toughness
Solution Approach 1:
The patent replaces mechanical processing methods (such as mechanical grinding or polishing) with chemical or plasma-based etching processes to form anti-reflective surface patterns in synthetic diamond. This substitution is necessary because mechanical methods would be too aggressive and damaging to the extremely hard and brittle diamond material, while chemical/plasma methods can precisely modify the surface without mechanical stress.
Solution Approach 2:
The patent changes the processing parameters by using controlled chemical etching or plasma treatment conditions that selectively modify the diamond surface morphology. By controlling parameters such as etch rate, surface temperature, and chemical composition, the process creates anti-reflective surface patterns while maintaining the bulk mechanical strength of the diamond material.
3Shape
If conventional processing methods are used to form anti-reflective surface structures in diamond material, then surface patterns are created, but significant surface and sub-surface crystal damage is introduced
Solution Approach 1:
The patent replaces mechanical surface modification methods with chemical or plasma-based processes that can selectively alter the diamond surface without mechanical impact. This substitution prevents the introduction of cracks, dislocations, and other crystal damage that would result from mechanical grinding or polishing, while still achieving the desired anti-reflective surface pattern.
Solution Approach 2:
The patent optimizes processing parameters such as etch depth, surface temperature, and chemical composition to create anti-reflective surface patterns that are confined to the very surface layer without penetrating deep into the bulk material. By controlling these parameters, the process achieves surface patterning while minimizing sub-surface damage that would compromise the diamond's mechanical and optical properties.
4Shape
If surface and sub-surface crystal damage is introduced in the synthetic diamond window, then anti-reflective surface structures are formed, but laser induced damage threshold and optical performance are reduced
Solution Approach 1:
The patent uses chemical or plasma-based surface modification methods instead of mechanical processing to create anti-reflective surface structures. This substitution ensures that the surface pattern is formed without introducing crystal damage into the bulk material, thereby maintaining the high laser induced damage threshold while achieving the desired optical performance.
Solution Approach 2:
The patent precisely controls surface treatment parameters to create anti-reflective structures with controlled depth and geometry that do not penetrate into the bulk material. By optimizing parameters such as etch depth, surface roughness, and pattern periodicity, the process achieves effective anti-reflection while keeping the bulk diamond material intact and free of damage that would reduce its damage threshold.
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 achieves low reflectance, high transmittance, and a high laser-induced damage threshold in synthetic diamond optical elements, suitable for high power laser applications, with minimal beam aberrations and improved optical performance, while being cost-effective and scalable.
Implementation Method 1
inductively coupled plasma reactive ion etching
Implementation Method 2
inductively coupled plasma reactive ion etching
Data Source
AI summary
An optical element comprising: synthetic diamond material; and an anti-reflective surface pattern formed directly in at least one surface of the synthetic diamond material, wherein the optical element has an absorption coefficient measured at room temperature of ≤0.5 cm−1 at a wavelength of 10.6 μm, wherein the optical element has a reflectance at said at least one surface of no more than 2% at an operating wavelength of the optical element, and wherein the optical element has a laser induced damage threshold meeting one or both of the following characteristics: the laser induced damage threshold 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 the laser induced damage threshold is at least 1 MW/cm2 measured using a continuous wave laser at a wavelength of 10.6 μm.