Interfering Laser Beam Shaping for Aberration-Compensated Machining
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Solution Overview
Problem
Existing methods for processing optical components using interfering laser radiation face limitations due to accumulated aberrations, which impair imaging quality and precision in structuring, and lack control over the spatial modulation of refractive index modifications.
Innovation Solution
A method and apparatus that utilize a collimated laser beam split into two partial beams, with a phase mask and adaptive optics to influence the intensity and phase distribution, allowing for aberration compensation and precise control of the interference pattern, enabling well-defined modifications with lower laser power and adjustable period progression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high numerical aperture optics are used to generate a well-defined focus, then the focal quality and intensity distribution are improved, but the accumulated aberration increases
Solution Approach 1:
A phase mask is introduced as an intermediary optical element between the laser beam and the focusing optics. This phase mask pre-modulates the wavefront to compensate for aberrations that will be accumulated during propagation and focusing, enabling high numerical aperture focusing while maintaining wavefront quality and reducing the harmful effects of aberrations on the focal spot
Solution Approach 2:
The phase mask performs preliminary wavefront shaping before the light enters the focusing system. By pre-correcting the wavefront phase distribution, the system anticipates and compensates for aberrations that will occur during propagation, allowing the use of high numerical aperture optics without suffering from degraded focal quality due to accumulated aberrations
2Manufacturing precision
If the angle between two focused partial beams is controlled to adjust the mean period, then the period of modification is improved, but the period progression (spatial modulation of period) cannot be controlled
Solution Approach 1:
The phase mask introduces spatially varying phase shifts across the laser beam profile, creating local variations in the interference pattern. This enables different regions of the processing zone to have different period progressions, providing spatial control over the modulation characteristics that cannot be achieved by uniform angle control alone
Solution Approach 2:
The phase mask dynamically modifies the phase distribution parameter across the beam cross-section, enabling control over both the mean period and the period progression. By varying the phase mask's optical path difference profile, the system can adjust multiple interference pattern parameters simultaneously, achieving versatile control over the modification structure
3Reliability
If a dynamic delay line is used to maintain coherence, then the coherence condition is improved, but the system complexity increases
Solution Approach 1:
The patent extracts the delay line from the optical path by using a common-path interferometer configuration where both partial beams travel through identical optical components. This eliminates the need for a dynamic delay line to maintain coherence, as the path length difference remains constant and negligible, thereby reducing system complexity while maintaining coherence
Solution Approach 2:
The optical paths of the two partial beams are merged through a common-path configuration where they share the same optical components including the phase mask and focusing optics. This merging of paths ensures that both beams experience identical optical conditions, maintaining coherence without requiring active delay control mechanisms
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 high-quality, precise modifications with improved imaging quality and adjustable period progression in optical components, reducing the impact of aberrations and achieving desired functionalities with lower laser power.
Implementation Method 1
The function of the phase mask is based on the fact that the phase shift of the laser radiation generated when passing through the plate is a function of the optical thickness
Implementation Method 2
The material of the component is heated locally limited by the high power of the laser pulses, whether up to the threshold at which a plasma is generated in the material by the individual laser pulse or below
Implementation Method 3
The interference pattern (hologram) created in the material is written into the material by the laser pulses
Data Source
AI summary
A method and an apparatus for processing an object by generation of laser radiation as a collimated laser beam, influencing the intensity distribution and/or the phase progression over the cross section of the laser beam, splitting the laser beam into two partial beams, and deflection and focusing of the partial beams so that the partial beams are superimposed in a processing zone in the material of the object.