Multi-Pulse Diffracted Laser Beam for Precision Photo-Disruption
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Solution Overview
Problem
Conventional photodisruptive treatments using single-pulse laser applications can result in imprecise incisions due to the expansion of damage areas caused by LIOB-induced cavitation bubbles, which complicates the precision of cutting in materials, including biological tissues like the eye.
Innovation Solution
A method employing a diffracted beam of pulsed laser radiation that generates photo-disruptions by irradiating a target position with a series of temporally offset pulses, each with a cross-sectional portion including a local intensity maximum, allowing for spatially overlapping and overlapping irradiation to create a multi-pulse effect without exceeding the single-pulse intensity threshold, thereby minimizing damage area and enhancing precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single-pulse laser application is used to create incisions in transparent material, then the incision can be created quickly, but the LIOB-induced cavitation bubbles expand the damage area beyond the focal volume, corrupting the precision of the incisions
Solution Approach 1:
The patent divides a single high-energy pulse into multiple lower-energy pulses applied in sequence to the same focal point. Each pulse contributes a portion of the total energy needed to reach the photodisruption threshold, while individual pulses remain below the threshold that would generate excessive cavitation. This segmentation of energy delivery allows cumulative damage at the target while limiting lateral damage from cavitation bubbles.
Solution Approach 2:
The patent employs periodic puling with specific pulse repetition frequencies to deliver multiple sub-threshold pulses to the same location. The periodic application of energy allows thermal and mechanical effects to accumulate over time while maintaining control over cavitation bubble formation. The pulse timing is optimized to allow partial dissipation of cavitation between pulses while building cumulative photodisruption effect.
2Manufacturing precision
If multiple pulses are applied to the same target position, then the cumulative effect can cause photo-disruption with smaller individual pulse energies, but the processing time increases compared to single-pulse application
Solution Approach 1:
The patent maintains continuous laser beam illumination at the target position by applying pulses in rapid succession without moving the beam away. This continuous action at the same focal point allows cumulative energy deposition and photodisruption buildup while minimizing idle time between pulses. The system keeps the laser engaged with the target throughout the multi-pulse sequence, maximizing processing efficiency.
Solution Approach 2:
The patent applies preliminary sub-threshold pulses that prepare the material by creating initial structural changes and reducing the threshold for subsequent pulses. These preliminary pulses modify the material properties at the focal point, making it more susceptible to photodisruption from later pulses in the sequence. This preliminary action reduces the total energy required and accelerates the overall process.
3Productivity
If the laser beam is scanned quickly across multiple target positions, then productivity increases, but the precision of maintaining the cutting plane orientation (parallel or inclined) deteriorates
Solution Approach 1:
The patent introduces temporal dimension to the processing by applying multiple pulses at each position before moving to the next position, rather than using a single pulse per position. This temporal stacking of pulses at each location allows the system to maintain precise spatial positioning and cutting plane orientation while still achieving high productivity through cumulative photodisruption. The time dimension compensates for the reduced scanning speed.
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 reduces the overall processing time for creating precise incisions in materials by allowing simultaneous processing of multiple target positions with reduced speed of transverse scanning, while maintaining precision and control over the cutting plane, whether parallel or inclined to the x-y plane.
Implementation Method 1
The photo-disruption originates from a physical phenomenon called laser-induced optical breakdown (abbreviated as LIOB) and is associated with mechanical effects including, but not limited to, cavitation resulting from plasma formation in the material being irradiated with laser radiation
Implementation Method 2
providing a diffracted beam of pulsed laser radiation; wherein each radiation pulse from the set of radiation pulses is incident at the target position with a cross-sectional portion of the diffracted beam, the cross-sectional portion including a local intensity maximum of the diffracted beam
Implementation Method 3
LIOB-induced cavitation bubbles may expand the damage area beyond the focal volume, corrupting the precision of the incisions made in the material
Data Source
AI summary
Embodiments of the invention provide a method and apparatus for laser-processing a material. In the embodiments, a diffraction-limited beam of pulsed laser radiation is diffracted by a diffraction device to generate a diffracted beam. The diffracted beam is subsequently focused onto the material and is controlled in time and space to irradiate the material at a target position with radiation from a set of radiation pulses of the diffracted beam so that each radiation pulse from the set of radiation pulses is incident at the target position with a cross-sectional portion of the diffracted beam, the cross-sectional portion including a local intensity maximum of the diffracted beam. The beam cross-sectional portions of at least a subset of the pulses of the set include each a different local intensity maxi-mum. In this way, a multi-pulse application for generating a photo-disruption at a target location of the material can be implemented.