Multi-Wavelength Laser Ablation for Crack-Free Glass Processing
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Solution Overview
Problem
Conventional methods for processing thin glass substrates using laser radiation often introduce additional stresses and cracks due to the diffractive and refractive effects of ablation depression surfaces, leading to roughening and damage during cutting or drilling processes.
Innovation Solution
A method employing a mixture of at least two wavelengths of laser radiation is used to reduce the intensity contrast in the ablation depression, ensuring that diffraction maxima of one wavelength align with minima of another, thereby minimizing the focusing effect and preventing excessive stress on the material, and adjusting the power and focus radii of the superimposed wavelengths to avoid crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser radiation with a single wavelength is used for ablation of brittle-hard material, then the ablation process is simple and efficient, but the diffractive and refractive effects at the ablation depression surfaces cause interference patterns that roughen the surface and induce cracks in the material
Solution Approach 1:
The laser radiation is segmented into multiple wavelength components. Instead of using a single wavelength, the invention employs at least two different wavelengths simultaneously or in sequence, which segments the interference pattern into non-coincident maxima and minima, thereby reducing the overall contrast and mitigating the harmful focusing effects that cause cracks and surface roughening.
Solution Approach 2:
The spectral parameter of the laser radiation is changed by introducing multiple wavelengths. This parameter change modifies the interference pattern characteristics, reducing the intensity contrast at the ablation depression surfaces and eliminating the conditions that lead to crack formation and excessive surface roughening while maintaining ablation efficiency.
2Productivity
If the power of laser radiation is increased to achieve higher removal rate, then the ablation speed increases, but the intensity at the leading edge exceeds the damage threshold and causes cracks to emanate from the leading edge
Solution Approach 1:
The laser radiation is applied in a periodic pulsed manner rather than continuously. This periodic action allows the material to cool between pulses, preventing excessive heat accumulation and stress buildup that would lead to crack formation from the leading edge, while still achieving high removal rates through repeated ablation cycles.
Solution Approach 2:
The laser processing parameters are made dynamic and adaptive. The power, pulse duration, and wavelength composition are adjusted in real-time based on the ablation progress and material response, allowing the process to maintain high removal rates while staying below the damage threshold and preventing crack formation.
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 allows for a high removal rate with minimal damage, reducing the occurrence of cracks and ensuring a smooth surface finish by reducing the intensity contrast and focusing effects at the ablation flanks, thus preventing material stress and damage.
Implementation Method 1
the surfaces of which have a diffractive and refracting effect on the introduced laser radiation and thus radiation components of this laser radiation generate interference diffraction patterns within the ablation indentation
Implementation Method 2
radiation components of this laser radiation generate interference diffraction patterns within the ablation indentation
Implementation Method 3
the surfaces of which have a diffractive and refracting effect on the introduced laser radiation
Implementation Method 4
Method for removing brittle-hard material by means of laser radiation in which an ablation depression is formed in the material as a result of the ablation
Implementation Method 5
an ablation depression is formed in the material as a result of the ablation
Data Source
Figure 1~2
Figure 3~4
Figure 5a~6
AI summary
The invention relates to a method for removing brittle-hard material by means of laser radiation, wherein a removal depression forms in the material as a result of the removal, the surfaces, also designated as flanks, of which removal depression have a diffractive and refractive effect on the laser radiation introduced and, as a result, radiation portions of said laser radiation generate interference diffraction patterns within the removal depression which, as soon as said radiation portions again impinge on the surfaces of the removal depression and penetrate into the material volume, bring about there a removal that is spatially variable along the surfaces, and as a consequence roughen the surface and induce cracks in the material volume. A wavelength mixture comprising at least two wavelengths is used as laser radiation for the removal, said wavelength being chosen such that interference diffraction patterns are established on account of the diffraction and refraction both along the surfaces of the removal depression and in the material volume in such a way that spatial positions of interference maxima of one wavelength (or more) fall within interference minima of the other wavelength(s).