Phase-Mask Laser Line Structuring With Lower Radiant Power Loss
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Solution Overview
Problem
Conventional methods for producing periodic structures using electromagnetic radiation are inefficient, as a significant portion of radiant power is lost at the diffraction grating, and Schwarzschild optics hide additional radiation power, limiting the effectiveness of the process.
Innovation Solution
A device comprising a pulsed laser, a phase mask that suppresses diffraction orders parallel to the optical axis, and imaging optics with a cylindrical lens to generate equidistant parallel lines by interference, ensuring that a predominant portion of the light is used efficiently, reducing near-axis light to enhance resolution and depth of focus, and prevent aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a diffraction grating is used to generate parallel lines, then periodic line structures can be produced, but a significant part of the radiant power is lost at the diffraction grating
Solution Approach 1:
The patent changes the fundamental parameter of light modulation from amplitude-based (diffraction grating) to phase-based (phase mask). The phase mask modulates the phase of incident light according to a rectangular profile in the transverse direction, creating interference patterns that form the periodic line structure. This phase modulation approach preserves radiant power much better than amplitude-based diffraction, as the phase mask is reflective rather than absorptive, and the interference pattern is formed by constructive and destructive interference rather than by blocking light.
Solution Approach 2:
The patent replaces the mechanical diffraction grating structure with an optical interference system using a phase mask and cylindrical lens. Instead of relying on physical diffraction at a grating surface, the system uses wave interference between two beams (from +1 and -1 diffraction orders of the phase mask) to create the periodic pattern. This substitution of the underlying physical mechanism eliminates the radiant power loss inherent in traditional diffraction grating approaches.
2Manufacturing precision
If Schwarzschild optic is used with diffraction grating, then imaging is achieved, but another large part of the radiation power is hidden
Solution Approach 1:
The patent extracts and eliminates the Schwarzschild optic from the optical system, replacing it with a much simpler arrangement: a phase mask positioned in the laser beam path and a cylindrical lens for imaging. By removing the complex Schwarzschild mirror system, the patent eliminates the associated radiant power losses while achieving the same imaging function through a different optical approach that uses interference of diffraction orders.
Solution Approach 2:
The patent segments the optical function into distinct components: the phase mask handles light modulation and interference pattern generation, while the cylindrical lens handles the imaging function. This segmentation allows each component to be optimized independently and eliminates the need for the complex integrated Schwarzschild optic system that was causing radiation power loss.
3Use of energy by moving object
If near-axis light is not suppressed, then total light output is maintained, but resolution and depth of focus are reduced and aberration occurs
Solution Approach 1:
The patent introduces a diaphragm (aperture stop) as an intermediary element in the optical path, positioned between the phase mask and the imaging plane. This diaphragm selectively blocks the near-axis light (zeroth diffraction order) while allowing the off-axis light (+1 and -1 diffraction orders) to pass through and form the interference pattern. The diaphragm acts as a mediator that filters the light based on its angular distribution, enabling high-resolution imaging by eliminating the problematic near-axis component that would otherwise cause aberration and reduce depth of focus.
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 solution allows for the efficient production of high-contrast, finer periodic line structures with improved resolution and depth of focus, while minimizing light loss and aberration, resulting in more effective use of ablative light for microstructure fabrication.
Implementation Method 1
a phase mask arranged in the optical path of the ablative light and adapted to generate a plurality of equidistant parallel lines in an object plane by interference
Implementation Method 2
the phase mask can generate the two beams. Each of the beams can correspond to a diffraction order
Implementation Method 3
a pulsed laser for generating ablative light; The equidistant parallel lines shown can create the periodic line structure on the workpiece by ablation
Data Source
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AI summary
The invention relates to an ablative production device and method for a periodic line structure on a workpiece (108). The device comprises a pulsed laser (109) for generating ablative light (110), a phase mask (102) arranged in the beam path of the ablative light (110), imaging optics (104) arranged on an optical axis (101), and a holder (106) to hold the workpiece (108) in an image plane (107). The phase mask (102) produces a plurality of equidistant parallel lines (112) in an object plane (103) by interference and suppresses an order of diffraction parallel to the optical axis (101). The optical axis (101) is perpendicular to the object plane (103). The imaging optics (104) comprises a cylindrical lens which is aligned in parallel to the lines (112) and is designed to image the object plane (103) into the image plane (107).