Laser Cutting of Transparent Materials with Shaped Femtosecond Beams
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Solution Overview
Problem
Existing methods for cutting and processing transparent materials, such as glass, face challenges in achieving precise geometry and orientation, particularly when creating small holes or cuts with high curvature, as they often result in irregular shapes and significant material deformation due to the accumulation of ablated material and unpredictable micro-cracks during chemical etching.
Innovation Solution
A two-phase method involving the use of ultra-short pulse laser radiation to create controlled damage areas followed by chemical etching, utilizing a birefringent optical element to generate a non-diffractive laser beam with an off-center symmetrical energy distribution, allowing for precise orientation and elongation of damage regions along the desired cut or split trajectory, which are then chemically processed for accurate separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional laser ablation is used for cutting transparent materials, then material removal is achieved, but the ablated material accumulates on walls and covers light access, preventing processing in narrow gaps
Solution Approach 1:
The patent changes the laser pulse duration parameter from conventional nanosecond or picosecond pulses to femtosecond pulses (10^-15 seconds). This ultra-short pulse duration enables precise material ablation with minimal heat diffusion, preventing molten material accumulation that would block subsequent laser access. The femtosecond laser creates clean ablation edges without the harmful material accumulation effect.
Solution Approach 2:
The patent employs periodic laser pulsing with carefully controlled duty cycles and repetition rates. By using periodic femtosecond pulses rather than continuous laser irradiation, the system allows time for material ejection between pulses and prevents heat buildup that would cause material to melt and accumulate on cavity walls, maintaining light access throughout the processing sequence.
2Object-affected harmful factors
If laser splitting separation is used to avoid material accumulation, then light access is maintained, but the method is limited for high curvature lines and hole drilling
Solution Approach 1:
The patent utilizes femtosecond laser parameters (pulse duration, energy density, repetition rate) that enable both ablation and splitting mechanisms to operate effectively. The ultra-short pulse duration and high peak power allow the laser to induce nonlinear optical effects and stress accumulation that lead to clean splitting without material accumulation, while maintaining the ability to process high curvature paths and drill holes by adjusting focal position and pulse energy.
3Volume of moving object
If acid or alkali etching is used to enlarge laser holes, then hole diameter increases, but the hole shape deviates from cylindrical with significant slopes
Solution Approach 1:
The patent performs preliminary laser drilling to create precise cylindrical holes with vertical walls before any chemical etching. The femtosecond laser ablation creates holes with excellent geometric fidelity (cylindrical shape, minimal slopes) as a preliminary structure. Subsequent chemical etching is then applied in a controlled manner to enlarge the holes while maintaining the preliminary cylindrical geometry as a template, resulting in larger holes that retain good geometric precision.
Solution Approach 2:
The patent applies chemical etching selectively and locally after laser drilling. By controlling the etching process parameters (etchant concentration, exposure time, temperature) and applying etching only where needed to enlarge specific regions, the method maintains the overall cylindrical geometry established by the laser while achieving the desired hole diameter increase without excessive slope formation.
4Manufacturing precision
If alkali etching is used to maintain hole geometry, then cylindrical shape is preserved, but the etching process becomes extremely slow requiring several hours
Solution Approach 1:
The patent uses femtosecond laser ablation as a preliminary action to create precise damage zones and micro-channels in the glass. These pre-formed structures provide defined pathways for subsequent chemical etching, allowing the etchant to rapidly penetrate and enlarge holes along predetermined trajectories. This preliminary laser structuring dramatically accelerates the overall hole enlargement process while maintaining geometric precision, eliminating the need for slow bulk chemical etching.
Solution Approach 2:
The patent merges laser ablation and chemical etching into a hybrid processing method. The femtosecond laser creates initial damage zones and micro-channels that serve as conduits for chemical etchants. This combination allows the etching process to proceed rapidly through the pre-formed pathways while the laser maintains geometric control, achieving both fast processing speeds and high geometric precision that neither method could achieve alone.
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 precise geometry cuts or holes with a cut width to depth ratio of up to 1:100 and minimal surface irregularities, significantly improving processing accuracy and speed, making it suitable for high-precision applications like semiconductor devices and microfluidic systems.
Implementation Method 1
Conventional laser microprocessing (drilling, cutting, or groove formation, etc.) methods generally rely on the removal of material due to focusing of the laser pulse energy in the affected area - the ablation
Implementation Method 2
Known analogues use acid or alkali etching of laser affected material
Implementation Method 3
the laser radiation beam transformation, according to the predetermined rule, takes place in an optical element (10), which comprises a birefringent structure that smoothly changes the Pancharatnam-Berry phase (PBP) of the perpendicular laser radiation beam
Data Source
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Figure 3~4
AI summary
The invention is related to fabrication of transparent materials by means of ultra-short laser pulses. Method to fabricate materials transparent in most part to laser wavelength comprises forming non-centrosymmetric, non-diffracting beam by optical element that contains at least two zones of birefringent structures changing Pancharatnam-Berry Phase according to the rule specific for that particular zone.The distribution of energy, phase and polarization depends on parameters of light approaching said element. Pulse energy is selected to employ main maximum of distributionto form voids elongated in desired direction while side maxima form changes of chemical character betveen damages from adjacent pulses. Void damages and zones of chemical changes form desired cut line. The workpiece prepared in said manner is placed in chemically aggresive solution, in which zones affected by laser light are dissolved much faster than non-affected ones. This enables achieving cuts with aspect ration up to 1/50.