Diffractive Laser Beam Combining With Precompensation for Beam Quality
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Solution Overview
Problem
Combining laser beams with different wavelengths results in a deterioration of beam quality due to non-ideal bandwidth, particularly in fiber lasers, leading to a deformed beam cross-section and reduced quality in the output beam.
Innovation Solution
A device comprising precompensation and combination units with diffractive optical elements that spatially sort and recombine spectral components, maintaining beam quality by utilizing diffraction effects to broaden and converge the beams without additional divergence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If spectral coupling is used to combine laser beams with different wavelengths, then the output beam contains all input wavelengths, but the beam quality deteriorates due to additional divergence from the diffractive optical element
Solution Approach 1:
The patent applies preliminary action by using a precompensation unit before the combination unit to pre-broaden the beam cross-section and pre-sort spectral components spatially. This anticipates the divergence that will occur in the combination unit and compensates for it in advance, ensuring that the final output beam maintains high quality while achieving spectral coupling.
Solution Approach 2:
The precompensation unit implements preliminary anti-action by introducing a controlled beam broadening that counteracts the harmful divergence introduced by the diffractive optical element in the combination unit. This opposite action is calculated to precisely cancel out the quality degradation that would otherwise occur during spectral coupling.
2Power
If fiber lasers with non-zero bandwidth are used as input sources, then high power can be achieved, but the beam quality deteriorates due to wavelength-dependent scattering
Solution Approach 1:
The precompensation unit performs preliminary action by detecting the input beam parameters and pre-broadening the beam cross-section in proportion to the square of the wavelength before the beam enters the combination unit. This anticipates and compensates for the wavelength-dependent scattering that would otherwise degrade beam quality, allowing high-power fiber lasers to be used without sacrificing beam quality.
3Adaptability or versatility
If multiple diffractive optical elements are used for beam combination, then spectral components can be combined, but additional divergence is introduced that degrades output beam quality
Solution Approach 1:
The precompensation unit implements preliminary action by pre-broadening the beam and pre-sorting spectral components before they enter the combination unit with multiple diffractive optical elements. This preparation reduces the complexity of the overall system by eliminating the need for complex adaptive optics or feedback mechanisms that would otherwise be required to correct the divergence introduced by multiple DOE elements.
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 maintains high beam quality in the output beam by compensating for non-ideal bandwidths, allowing for the combination of multiple input laser beams with intrinsic beam qualities, even at high power levels.
Implementation Method 1
The precompensation unit has at least one diffractive optic, which expands the respective input laser beam into an associated, broadened intermediate beam bundle
Implementation Method 2
the first diffractive optical element converts each intermediate beam into a convergent beam with a beam waist by diffraction
Implementation Method 3
The second diffractive optical element is then designed and arranged in such a way that all incident spectral components are deflected into a common radiation direction
Data Source
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AI summary
The invention relates to a device (18) for combining at least two input laser beams (16; 16-1,...,16-n) having different spectral components, comprising: - at least one pre-compensation unit (20) for the at least two input laser beams (16), comprising a diffractive optical unit (28) which expands the input laser beam (16) into an intermediate beam bundle (22), in which the spectral components are spatially arranged so as to be adjacent to one another with increasing wavelength (λ1, λ2, λ3); - a combination unit (24), comprising at least a first diffractive optical element (48) and a second diffractive optical element (50), the combination unit (24) being aligned with the pre-compensation unit (20) in such a way that the first diffractive optical element (48) converts an intermediate beam bundle (20) into a convergent beam bundle (52) having a beam waist (54), the beam waist (54) lying on the second diffractive element (50), and the second diffractive optical element (50) being designed in such a way that all incident spectral components are diffracted into a common radiation direction (26).