Second-Surface Laser Ablation for Low-Diffraction Periodic Structures
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Solution Overview
Problem
Laser ablation processes often produce undesired diffraction effects on the surface of workpieces due to artifacts with periodic arrangements, which can be objectionable and affect the quality of products like electrochromic devices.
Innovation Solution
A laser ablation process that controls the energy delivery and movement of the laser beam to minimize the formation of artifacts with periodic structures, reducing diffraction severity by optimizing parameters such as peak-to-valley distance and refractive index of adjacent media, thereby reducing diffraction severity to less than 5.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser ablation is performed with conventional parameters, then material removal is achieved, but artifacts with periodic structures are formed causing diffraction effects
Solution Approach 1:
The patent applies parameter changes by modifying laser process parameters including pulse duration (50-500 ps), repetition rate (100-500 kHz), peak power (5-50 kW), and scanning speed (1-10 m/s) to eliminate periodic artifacts and reduce diffraction effects while maintaining ablation efficiency
Solution Approach 2:
The patent uses periodic pulsed laser action with optimized pulse duration and repetition rate to achieve continuous wave equivalent power levels, creating uniform ablation without periodic artifacts that cause diffraction
2Productivity
If laser power is increased to improve ablation speed, then productivity increases, but diffraction severity increases
Solution Approach 1:
The patent employs high-repetition-rate pulsing (100-500 kHz) that allows continuous processing at high productivity while maintaining parameter conditions that prevent periodic artifact formation, thus avoiding diffraction effects even at high power levels
Solution Approach 2:
The patent dynamically adjusts multiple parameters including pulse duration, repetition rate, and scanning speed in combination to achieve high ablation speeds without creating the periodic structures that cause diffraction, moving beyond static parameter settings
3Use of energy by moving object
If pulse duration is extended to increase energy delivery, then ablation efficiency improves, but periodic artifacts are enhanced causing more severe diffraction
Solution Approach 1:
The patent uses high-frequency periodic pulsing (100-500 kHz) with short duration (50-500 ps) to deliver continuous energy equivalent to high-power continuous wave lasers while preventing the accumulation of thermal effects that create periodic artifacts and diffraction
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 process effectively minimizes diffraction severity, enhancing the quality of laser-ablated products by reducing objectionable diffraction effects, ensuring they meet stringent quality metrics and are suitable for applications like automotive rearview mirrors.
Implementation Method 1
A laser ablation process generally includes selective removal of material at a surface of a workpiece by directing a laser beam at the workpiece
Implementation Method 2
This controlled amount of energy is selected to liquefy, vaporize, or otherwise rapidly expand the surface material at the laser spot to cause it to separate from the workpiece for removal
Data Source
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Figure 3a~4b
Figure 5~7A
AI summary
A laser ablated product exhibits a diffraction severity of less than about 5. The product may include a substrate that is at least partially transparent to visible light, and a periodic structure formed on at least one surface of the substrate by laser ablation. The periodic structure has a period in at least one direction of at least about 4,500 nm to at most about 850,000 nm, and the periodic structure has a peak-to-valley dimension of less than about 25 nm. The product may be employed in an electrochromic device, such as a vehicle rearview mirror assembly.