Laser Focal-Line Cutting of Glass Through Narrow Apertures
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Solution Overview
Problem
Current laser cutting methods for glass substrates, particularly using non-diffracting Bessel beams, face challenges in minimizing the laser-affected zone (LAZ) to cut through narrow apertures without damaging pre-existing surface features, and often result in unwanted damage, surface planarity issues, and glass strength degradation, limiting parallel processing and requiring corrective processing steps.
Innovation Solution
A method involving a pulsed laser beam focused into a focal line with varying deflection angles and radii, using an optical arrangement that includes a spatial light modulator or diffractive optical element, to create a defect line within the glass substrate, allowing for precise cutting and separation near sensitive structures without damaging them, by generating induced absorption and nonlinear absorption processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a Bessel beam with fixed deflection angle is used to cut through glass, then the beam can penetrate the entire thickness, but the laser-affected zone (LAZ) becomes large (500 μm to 1 mm), severely restricting the minimum street width
Solution Approach 1:
The patent applies dynamics by continuously varying the beam deflection angle along the propagation direction. The optical system uses a gradient index (GRIN) lens or axicon with a specific refractive index profile that causes the beam to transition from a larger deflection angle at the entrance (for sufficient penetration) to a smaller deflection angle deeper in the material (for reduced LAZ). This dynamic adjustment of the beam parameter along the depth direction resolves the contradiction between maintaining penetration capability and reducing the affected zone width.
Solution Approach 2:
The patent changes the beam deflection angle parameter as a function of depth within the glass substrate. By using optical elements with graded refractive indices, the effective deflection angle is modified continuously along the beam path, allowing the beam to maintain adequate penetration at shallow depths while minimizing the LAZ at greater depths where the cutting action is most critical.
2Area of stationary object
If the beam width is reduced to decrease LAZ, then the laser-affected zone becomes smaller, but the beam deflection angle must be reduced, resulting in insufficient laser damage to cut the glass
Solution Approach 1:
The patent dynamically adjusts the beam characteristics by using a gradient index optical element that modifies the deflection angle as a function of depth. This allows the beam to maintain an optimal balance between width and penetration capability at different depths, ensuring sufficient damage accumulation for effective cutting while keeping the LAZ minimized where it matters most for feature preservation.
Solution Approach 2:
The patent applies preliminary action by creating a cone-shaped damage region that precedes the final cut. The varying deflection angle ensures that sufficient energy is deposited throughout the glass thickness to create a continuous defect line, while the reduced beam width at deeper levels minimizes the LAZ. This preliminary damage accumulation enables successful cutting without requiring a uniformly large beam width throughout the entire path.
3Area of stationary object
If the beam deflection angle is reduced to decrease LAZ, then the laser-affected zone becomes smaller, but weak damage areas form below the glass entrance surface and ablation effects occur on the surface
Solution Approach 1:
The patent changes the beam deflection angle parameter continuously along the depth direction using gradient index optics. This ensures that the beam maintains adequate deflection at shallow depths to prevent weak damage formation and surface ablation, while transitioning to smaller deflection angles at greater depths to minimize the LAZ. The gradual parameter change avoids abrupt transitions that could cause unwanted surface effects.
Solution Approach 2:
The dynamic variation of beam parameters through the glass thickness allows the system to adapt to different depth requirements. Near the surface, larger deflection angles ensure sufficient damage for reliable cutting initiation without ablation, while deeper in the material, smaller angles minimize the LAZ. This dynamic adaptation maintains both surface quality and cutting reliability throughout the entire processing depth.
4Ease of manufacture
If laser processing is performed on bare substrates with non-diffracting beams, then cutting can be achieved, but undesired damage occurs including reduced surface planarity, roughness, surface debris, and glass strength degradation
Solution Approach 1:
The patent uses parameter changes by varying the beam deflection angle as a function of depth to concentrate the cutting action primarily within the bulk material rather than at the surface. This depth-dependent parameter modulation ensures that the most intense damage occurs inside the glass where it contributes to clean separation, while surface-level effects are minimized, reducing debris and maintaining surface quality.
Solution Approach 2:
The patent applies local quality by creating different beam characteristics at different depths within the glass substrate. The varying deflection angle produces a cone-shaped energy distribution that is more intense in the bulk material and less intense near the surfaces. This localized quality variation ensures effective cutting in the interior while preserving surface integrity, eliminating the need for corrective processing steps.
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 method enables precise cutting and separation of glass substrates with reduced LAZ, minimizing damage to pre-fabricated structures, improving surface quality, and enabling parallel processing, while maintaining the integrity of surface features and glass strength.
Implementation Method 1
the laser beam focal line generating an induced absorption within the glass substrate, and the induced absorption producing a defect line along the laser beam focal line within the substrate
Data Source
AI summary
The present invention relates to a method of laser processing a glass substrate, the method comprising: focusing a pulsed laser beam into a laser beam focal line into the glass substrate, the glass substrate having a feature formed on a first surface of the glass substrate, wherein a first portion of the laser beam focal line is focused at the first surface of the glass substrate and a second portion of the laser beam focal line is focused at a second surface of the glass substrate that is opposite the first surface, wherein a first set of rays exiting the optical arrangement at a first radius R1, as measured from a center of the optical arrangement forms the first portion of the laser beam focal line with a deflection angle of θ1, wherein a second set of rays exiting the optical arrangement at a second radius R2, as measured from the center of the optical arrangement forms the second portion of the laser beam focal line with a deflection angle of θ2, wherein R1 is less than R2; and wherein θ1 is greater than θ2, and wherein θ1 decreases to θ2 from R1 to R2 in one of a step-wise decrease or a graded decrease; and translating the glass substrate and the laser beam relative to each other along a first contour, thereby laser forming a plurality of defect lines along the first contour within the substrate.