Multi-Metal Reflective Diffraction Grating for High Peak Laser Flux
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Solution Overview
Problem
Existing diffraction gratings used in high-energy ultra-short pulse lasers face limitations in laser flux resistance and spectral bandwidth, with conventional gold gratings suffering from limited efficiency and MLD gratings being complex and expensive, while current models fail to predict performance under intense laser flux.
Innovation Solution
A reflective diffraction grating with a stack of two metallic layers, comprising a reflective outer layer and an intermediate layer with different metals, optimized for electron-phonon coupling and thermal resistance, to enhance flux resistance and spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single gold layer is used for the reflective coating, then diffraction efficiency is high, but laser flux resistance is limited
Solution Approach 1:
The patent uses a composite metallic coating structure consisting of multiple layers with different materials (e.g., gold, silver, aluminum, nickel, chromium) and different thicknesses. This composite structure combines the high reflectivity of gold in the infrared range with the high laser damage threshold of metals like nickel and chromium, achieving both high diffraction efficiency and improved laser flux resistance that cannot be obtained with a single material layer.
Solution Approach 2:
The patent optimizes the thickness parameters of each metallic layer to achieve the desired performance. By carefully controlling the thickness of each layer (e.g., gold layer 50-200 nm, nickel layer 10-50 nm, chromium layer 5-20 nm), the coating maintains high diffraction efficiency while the total thickness and material composition provide enhanced resistance to laser-induced damage compared to conventional single-layer coatings.
2Reliability
If MLD gratings are used to improve flux resistance, then resistance to laser flux increases, but spectral bandwidth becomes too limited
Solution Approach 1:
The patent employs a composite metallic coating structure that combines the advantages of different metals: gold provides high reflectivity and broad spectral coverage in the infrared range, while nickel and chromium contribute high laser damage thresholds. This metallic composite approach maintains broad spectral bandwidth unlike dielectric MLD coatings, while achieving improved flux resistance through the high damage threshold materials.
Solution Approach 2:
The patent applies different materials with specific properties to different layers: the outer gold layer optimizes for broad spectral reflectivity, while the underlying nickel and chromium layers provide localized high damage threshold protection. This layered approach with differentiated material properties achieves both broad bandwidth and high flux resistance.
3Ease of manufacture
If conventional metal gratings are used, then manufacturing is simple, but diffraction efficiency is insufficient
Solution Approach 1:
The patent uses a multi-layer metallic coating structure that can be deposited using conventional vacuum coating techniques, maintaining manufacturing simplicity. The composite structure of gold, nickel, and chromium layers achieves diffraction efficiency superior to conventional single-layer metal gratings, as the optimized thickness and material combination enhance reflectivity and reduce absorption losses.
4Reliability
If the reflective layer thickness is increased to improve flux resistance, then resistance to laser flux increases, but diffraction efficiency decreases
Solution Approach 1:
The patent uses a composite metallic coating structure consisting of multiple layers with different materials (e.g., gold, silver, aluminum, nickel, chromium) and different thicknesses. This composite structure combines the high reflectivity of gold in the infrared range with the high laser damage threshold of metals like nickel and chromium, achieving both high diffraction efficiency and improved laser flux resistance that cannot be obtained with a single material layer.
Solution Approach 2:
The patent optimizes the thickness parameters of each metallic layer to achieve the desired performance. By carefully controlling the thickness of each layer (e.g., gold layer 50-200 nm, nickel layer 10-50 nm, chromium layer 5-20 nm), the coating maintains high diffraction efficiency while the total thickness and material composition provide enhanced resistance to laser-induced damage compared to conventional single-layer coatings.
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 multi-metallic diffraction grating achieves improved resistance to ultra-short pulse laser flux and extended spectral bandwidth, capable of withstanding higher fluences and maintaining high diffraction efficiency.
Implementation Method 1
The combination of the reflective outer layer and the intermediate layer and their respective thicknesses are thus chosen so as to locally reduce the temperature in the reflective outer layer. The combination of thin layers of different metals makes it possible to shift the thermal equilibrium location and to concentrate the thermal energy induced by the laser-matter interaction, preferentially at the level of the metallic intermediate layer.
Implementation Method 2
The intermediate layer is made of another metal, the other metal having an electron-phonon coupling coefficient greater than the electron-phonon coupling coefficient of the first metal
Implementation Method 3
The present invention provides a reflective diffraction grating resistant to a high peak power ultra-short pulse light flux, the diffraction grating comprising grating features formed on a surface of a substrate
Data Source
Figure 1~3
AI summary
The invention concerns a reflective diffraction grating comprising at least one intermediate metal layer (14) arranged between an outer reflective layer (13) and a surface (10) of the substrate comprising the grating lines (11), the outer reflective layer (13) being formed of a first metal and a metal alloy and the intermediate metal layer (14) being formed of another metal, the other metal having an electron-phonon coupling coefficient greater than the electron-phonon coupling coefficient of the first metal or metal alloy, the outer reflective layer (13) having a thickness in a range having a lower limit determined by a reflection coefficient of the first metal and an upper limit determined by a thermal diffusion length of the first metal, and the intermediate metal layer (14) having another thickness greater than a minimum value so as to increase the resistance of the reflective diffraction grating to an ultra-short-pulse light flux with high peak power.