Second-Surface Laser Ablation for Low-Diffraction Mirror Electrodes
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Solution Overview
Problem
Laser ablation processes often produce artifacts on the workpiece surface that create undesirable diffraction patterns, particularly when the diffraction severity exceeds 5, which can be objectionable in certain applications such as electrochromic devices used in vehicle rearview mirrors.
Innovation Solution
The process involves subjecting a conductive layer on a substrate to laser ablation to form a periodic structure with specific dimensions, such as a period between 4,500 nm and 850,000 nm, and a peak-to-valley dimension of less than 25 nm, while maintaining a diffraction severity of less than 5, often achieved by using a picosecond laser and optimizing laser parameters like pulse width and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser ablation is used to form periodic structure on conductive layer, then surface precision and optical clarity are improved, but diffraction artifacts are generated
Solution Approach 1:
The patent applies parameter changes by precisely controlling laser ablation parameters including pulse width (picosecond range), energy density, scan speed, and overlap percentage to create periodic structures with specific dimensions (4,500-850,000 nm period, less than 25 nm peak-to-valley) that minimize diffraction severity below threshold of 5, thus resolving the contradiction between achieving surface precision and avoiding diffraction artifacts
Solution Approach 2:
The patent employs periodic action by using pulsed laser ablation to create periodic structures on the conductive layer surface. The controlled periodicity of the ablation process (through pulse repetition and scan patterns) generates the desired microstructure while maintaining diffraction severity within acceptable limits, addressing both the precision requirement and the harmful diffraction effect
2Illumination intensity
If periodic structure with small peak-to-valley dimension is created, then optical clarity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent replaces complex mechanical machining or multi-step manufacturing processes with laser ablation technology. The laser system can precisely create the required periodic structures with small peak-to-valley dimensions (less than 25 nm) through optical field interaction, eliminating the need for complex mechanical tooling and multiple processing steps, thus achieving optical clarity while managing manufacturing complexity
3Object-generated harmful factors
If diffraction severity is reduced to less than 5, then visibility of diffraction effects is minimized, but laser process control becomes more difficult
Solution Approach 1:
The patent implements feedback control mechanisms to monitor and adjust laser ablation parameters in real-time, ensuring that the periodic structures created maintain diffraction severity below 5. The system uses feedback from process monitoring and quality measurement to optimize pulse width, energy density, and scan parameters, making the control process more manageable despite the precision requirements
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
This approach reduces the diffraction severity to acceptable levels, minimizing the visibility of diffraction effects in electrochromic devices, ensuring improved optical clarity and functionality, particularly in automotive applications.
Implementation Method 1
The ablated surface is formed by subjecting the conductive layer to laser ablation
Data Source
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.