Spiral Beam Shaper Optic for Uniform Ring Laser Processing
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Solution Overview
Problem
Existing optical beam shaping elements, such as axicons and Siemens star beam shapers, suffer from alignment sensitivity and poor transmission efficiency, leading to hot spots in laser material processing applications, which result in local damage and poor quality finishes.
Innovation Solution
A refractive or reflective optical beam shaping element with a twisted Siemens star configuration, featuring curved sector-shaped facets that radiate outward in a spiral star pattern, eliminating hot spots by spreading concentrated light uniformly across an annular ring distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If classic axicons or Siemens star beam shapers are used to generate ring-shaped intensity distribution, then the laser beam can be transformed into an annular profile, but hot spots are created at the focal plane leading to local damage and poor quality finishes
Solution Approach 1:
The patent applies curvature to the sector-shaped facets of the beam shaper optic. Instead of using straight edges radiating from the center, the facets are curved to create a spiral or swirl pattern. This curvature redistributes the light intensity more uniformly across the annular ring, eliminating the hot spots that occur with straight-edged Siemens star designs. The curved facets modify the phase distribution of the laser beam to achieve a more uniform intensity profile at the focal plane.
2Shape
If single axicons are used to convert gaussian energy distribution to annular distribution, then the beam shaping function is achieved, but the system becomes highly sensitive to alignment and input intensity distribution variations
Solution Approach 1:
The beam shaper optic is divided into multiple discrete sector-shaped facets arranged in a circular pattern around the optical axis. Each facet is independently configured with specific curvature and orientation. This segmentation allows the system to be more tolerant of alignment variations and input beam parameter changes, as the collective action of multiple facets produces the desired annular distribution even when individual facets are not perfectly aligned. The segmented structure provides inherent robustness against misalignment.
3Shape
If diffractive optical beam shaping elements are used to impose phase distribution on laser beam, then beam shaping is achieved, but transmission efficiency is poor at 75-95% and the system is wavelength dependent
Solution Approach 1:
The patent replaces diffractive optical elements with a refractive beam shaper design. Instead of using diffraction to achieve beam shaping, the invention uses refraction through precisely configured sector-shaped facets. This substitution of the underlying optical mechanism eliminates the wavelength dependence and transmission efficiency losses associated with diffractive elements. The refractive approach directs light through the facets with minimal loss, achieving near-100% transmission efficiency while maintaining the desired annular beam shape.
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 twisted Siemens star configuration achieves a uniform ring-shaped intensity distribution at the focal plane, reducing hot spots and improving the quality of laser material processing by maintaining uniform illumination and reducing skew components in the beam.
Implementation Method 1
A refractive or reflective optical beam shaping element with a twisted Siemens star configuration, featuring curved sector-shaped facets that radiate outward in a spiral star pattern
Data Source
AI summary
An optical beam shaping element to perform beam shaping of multi-mode laser beams where a uniform ring-shaped intensity distribution is produced at a focal length of a focusing lens. The optical beam shaping element with a surface having radial arms which are twisted to be curved in comparison to a known Siemens star beam shaper giving a spiral configuration. Embodiments are described in which each of the arms in the spiral structure is additionally modified with radially varied slope and/or curvature to optimise far field distribution. Relative rotation between two optical beam shaping elements forms an adjustable trident to vary power between the ring and a centre spot. The optical beam shaping element finds application in laser material processing were the spiral curvature removes hotspots and can be configured to improve through focus performance and input sensitivity.