Spectral Beam Combiner Alignment via Longitudinal Source Spacing
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Solution Overview
Problem
Combining and co-aligning multiple laser beams of different wavelengths becomes increasingly complex and costly as the number of wavelengths and spectral range increase, with traditional dichroic mirrors requiring precise alignment and limited spectral bandwidth, while spectral beam combining methods face challenges in maintaining beam divergence and quality.
Innovation Solution
The apparatus allows for longitudinal spacing of radiation sources relative to the collimator element, enabling precise positioning of each source at its correct focal length to correct geometric aberrations and achieve co-alignment, using a mount with V-shaped channels and a translation stage to adjust the position of waveguides, and employing a diffraction grating or prism for combining the beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dichroic mirrors are used to combine and co-align multiple laser beams of different wavelengths, then beam combination is achieved, but the system complexity and cost increase significantly as the number of wavelengths and spectral range increase
Solution Approach 1:
The patent merges multiple laser beams of different wavelengths into a single spatial path using a beam combining apparatus. The collimator element combines the collimating function, while the diffractive optical element combines the wavelength-specific routing function that would otherwise require multiple dichroic mirrors, thereby reducing overall system complexity while maintaining spectral versatility
Solution Approach 2:
The diffractive optical element serves multiple functions simultaneously: it acts as a beam combiner, a wavelength separator, and a beam steering element. This multi-functional component replaces what would traditionally require multiple specialized optical elements (dichroic mirrors), reducing system complexity while handling broad spectral ranges
2Adaptability or versatility
If dichroic mirrors are used for beam combination, then beam combination is achieved, but alignment precision becomes increasingly difficult to maintain as more wavelengths are added
Solution Approach 1:
The patent merges the alignment reference function into the diffractive optical element itself. Since all wavelength-specific routing is handled by the DOE's diffraction patterns rather than multiple dichroic mirrors, there is a single alignment reference (the DOE geometry) rather than multiple sequential alignment references, thereby maintaining precision as the number of wavelengths increases
3Measurement precision
If a diffraction grating is used as the dispersive element in spectral beam combining, then high spectral dispersion is achieved, but the spectral bandwidth is limited due to diffraction order overlap
Solution Approach 1:
The patent changes the operational parameters of the diffractive optical element by using a reflective configuration rather than transmission, and by optimizing the groove density and blaze angle. This allows the DOE to achieve high spectral dispersion while accommodating broader spectral bandwidths without diffraction order overlap, as the reflective geometry provides better control over beam paths for different wavelengths
4Adaptability or versatility
If a prism is used as the dispersive element in spectral beam combining, then wide spectral bandwidth is achieved, but spectral dispersion is reduced limiting the ability to combine closely spaced wavelengths
Solution Approach 1:
The patent changes from a prism-based dispersive element to a diffractive optical element with optimized parameters. The DOE's groove density, blaze angle, and reflective configuration are specifically designed to provide high spectral dispersion while maintaining broad spectral bandwidth capability, overcoming the inherent trade-off present in prism-based systems
5Device complexity
If radiation sources are positioned at a single focal plane, then the optical path is simplified, but beam quality and divergence deviate from requirements due to focal length variations across different wavelengths
Solution Approach 1:
The patent introduces longitudinal spacing along the optical axis as an additional degree of freedom for positioning radiation sources. Instead of constraining all sources to a single focal plane, the system allows sources to be positioned at different longitudinal positions, each optimized for its specific wavelength's focal length requirement. This dimensional addition enables correction of geometric aberrations and optimization of beam quality for each wavelength while maintaining a relatively simple optical path
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 improves beam quality and efficiency by ensuring each radiation source is positioned correctly, minimizing aberrations and achieving effective co-alignment across a broad spectral range, enhancing the combination of power from separated radiation beams.
Implementation Method 1
a collimator element (13) which is arranged to receive the radiation beams (11a-c) from the radiation sources (12a-c)
Implementation Method 2
a diffractive optical element (14) which is arranged to combine the collimated beams into a single co-aligned beam
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
Apparatus and method are disclosed for co-aligning a number of laterally displaced radiation beams from respective radiation source outputs, each beam having a respective waveband. The apparatus comprises a collimating element for receiving each of said radiation beams with respective lateral displacements and a combining element for receiving each of said radiation beams passed by said collimating element. The apparatus further comprises a radiation source mount for positioning the radiation source outputs relative to the collimating element. The method comprises longitudinally positioning the radiation source outputs upon the mount, relative to the collimating element,in dependence upon the waveband of each beam, to cause the radiation beams passed by the combining element to be co-aligned.