Ultrafast Laser Writing of Periodic Structures Without Bifurcation
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Solution Overview
Problem
Current methods for generating highly regular periodic nanostructures on metallic surfaces via laser ablation face challenges such as loss of regularity, double periodicity, and bifurcation points, limiting their application in fields like microelectronics and photovoltaics due to insufficient structural uniformity and high-speed writing capabilities.
Innovation Solution
The method involves selecting specific conditions for laser pulse duration, illuminated area size, laser fluence, and dielectric permittivity to induce strong ablation while maintaining coherence of surface electromagnetic waves, ensuring highly regular periodic structures with minimal bifurcation points and high scanning speed by adjusting overlap and repetition rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional laser ablation methods are used to generate periodic structures, then processing speed can be increased, but structural regularity and uniformity deteriorate due to loss of coherence and appearance of bifurcation points
Solution Approach 1:
The patent applies parameter changes by carefully controlling laser pulse duration (ultrafast regime), fluence (above ablation threshold), and repetition rate to maintain surface electromagnetic wave coherence during ablation. These parameter optimizations enable high-speed processing while preserving structural regularity with FFT dispersion angles below 15 degrees, eliminating the trade-off between speed and precision.
2Productivity
If laser fluence is increased to improve ablation efficiency, then processing speed increases, but excessive molten substrate formation occurs leading to loss of periodic structure regularity
Solution Approach 1:
The patent optimizes laser fluence to be above the ablation threshold but carefully controlled to induce strong ablation without excessive molten substrate formation. This precise fluence control maintains the periodic absorption profile on the metallic surface, achieving high ablation efficiency while preserving structural regularity.
3Area of stationary object
If overlapping scanning is used to cover large areas, then coverage area increases, but regularity is lost due to accumulation of deviations across multiple scan lines
Solution Approach 1:
The patent employs preliminary action by using a small illuminated area (diameter ≤ 30 μm) that maintains surface electromagnetic wave coherence across the entire illuminated region. This coherent interaction ensures that periodic structures are formed with high regularity from the beginning, and this regularity is consistently reproduced across multiple overlapping scan lines, achieving uniform coverage over large areas with FFT dispersion angles below 15 degrees.
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 enables ultrafast writing of highly regular periodic structures with reduced angle dispersion and no bifurcation points, achieving high regularity and uniformity on large areas, suitable for industrial applications in photovoltaics and microelectronics.
Implementation Method 1
The fluence is selected so that strong the ablation of the substrate is induced with avoiding formation of excessive volume of molten substrate
Implementation Method 2
strong the ablation of the substrate is induced
Implementation Method 3
providing a high degree of coherence of the surface electromagnetic waves
Implementation Method 4
preserving the said periodic absorption profile on the metallic surface
Data Source
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AI summary
A method, a product by the method and device of preparation of highly-regular periodic structure using a pulsed laser beam irradiating a spot on a surface of a substrate are disclosed. The method of direct formation of highly-regular periodic structure on a materials uses activation of Surface Electromagnetic Wave (SEW) interfering with the laser beam on the surface of the substrate in a manner which ensures high quality and regularity of the obtained pattern.