Helical Phase Front Laser Cutting Transparent Materials
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Solution Overview
Problem
Current laser cutting technologies for transparent materials, particularly in biological tissues like the eye, face challenges in achieving precise cuts perpendicular to the laser light direction with minimal energy dose and high precision, leading to photochemical and photomechanical side effects.
Innovation Solution
A laser cutting device that converts linearly polarized Gaussian beams into helical phase front beams, producing a toroidal plasma generation region with a larger focal diameter, allowing for fewer grid points and reduced total energy usage, thereby increasing cutting speed and minimizing side effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional Gaussian beam focusing is used, then the laser can be focused to a small spot size for precise energy deposition, but the focal diameter is limited requiring many grid points and high total energy for perpendicular cuts
Solution Approach 1:
The patent transforms the laser beam from a conventional Gaussian profile to an azimuthally polarized profile with helical phase front. This parameter change in beam structure fundamentally alters the focal characteristics, producing a toroidal focus with larger diameter that reduces the number of grid points needed while maintaining cutting precision.
Solution Approach 2:
The invention introduces a new dimensional characteristic to the focal volume by creating a toroidal (doughnut-shaped) focus instead of a conventional point focus. This dimensional change in the focal geometry enables larger focal diameter perpendicular to the beam direction, allowing fewer spots to cover the same cutting area.
2Manufacturing precision
If conventional Gaussian beam focusing is used, then the focus is concentrated in a small volume, but the cutting speed is reduced due to the large number of spots required for perpendicular cuts
Solution Approach 1:
By changing the beam polarization and phase structure to azimuthal polarization with helical phase front, the patent achieves a toroidal focus that maintains precise energy deposition while expanding the focal diameter. This parameter change directly increases cutting speed by reducing the number of spots required.
3Productivity
If high energy density is used to reduce the number of spots, then the cutting speed increases, but photochemical and photomechanical side effects increase
Solution Approach 1:
The patent changes the beam parameters to azimuthal polarization and helical phase front, which redistributes the energy density in a toroidal pattern. This parameter change allows using lower peak energy densities while achieving the same cutting effect with fewer spots, thereby reducing photochemical and photomechanical side effects.
4Productivity
If the focal diameter is increased to reduce the number of grid points, then the cutting speed increases, but the precision of energy localization may be compromised
Solution Approach 1:
By transforming to azimuthal polarization with helical phase front, the patent achieves a toroidal focus that simultaneously provides larger diameter for speed and maintains sharp energy localization through the structured phase distribution, resolving the apparent contradiction between size and precision.
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
The device achieves precise cuts with fewer spots and lower energy doses, enhancing cutting speed and reducing adverse mechanical and photochemical side effects, particularly beneficial for UV lasers in eye surgery by optimizing radiation dose and improving axial cutting precision.
Implementation Method 1
a localized energy deposition can be carried out by multi-photon processes in the form of multiphoton ionization and avalanche ionization
Implementation Method 2
multi-photon processes in the form of multiphoton ionization and avalanche ionization
Implementation Method 3
the plasma formation rate above a threshold, which depends on material and laser parameters, increases extremely strongly, the plasma formation process in this parameter range is also referred to as 'optical breakdown'
Implementation Method 4
At each grid point (in the following also: spot), plasma is generated, which disintegrates the transparent material in the focal volume
Data Source
AI summary
A laser cutting device for transparent material (23), which device is designed to focus the laser light (2) into a plurality of predetermined spots within the material (23), wherein the spots lie on a predetermined cutting line or cutting area (24) running substantially perpendicularly to the direction of incidence of the laser light (2), wherein the device comprises means for mode conversion (3) into laser light having a helical phase front (5), which means can be brought into and out of the beam path of the laser light (2).