Transmission Grating Beam Combiner for High Power Scaling
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Solution Overview
Problem
Current optical beam combining technologies face challenges in efficiently combining beams of the same or different wavelengths with narrow or broad linewidths, particularly with crystal gain media like YLF and YAG, and high-power fiber lasers, while maintaining high beam quality and power scaling without damaging the beam combiners.
Innovation Solution
The use of transmission gratings in a non-Littrow orientation, configured for +1 and −1 diffraction orders, to combine optical beams into a single superimposed output with high efficiency, potentially exceeding 90% efficiency, and allowing for cascaded arrangements to increase the number of combinable beams exponentially.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If dielectric layered beam splitters are used to combine same wavelength beams, then combining efficiency is improved (90%+), but the beam combiner has a low damage threshold and cannot combine additional beams
Solution Approach 1:
The patent changes the fundamental operating parameters of the beam combiner by using transmission gratings in a non-Littrow geometry, where the incident and diffracted beams are separated. This geometric parameter change allows the system to achieve both high efficiency (90%+) and high damage threshold, while also enabling the combination of multiple beams beyond the two-beam limitation of dielectric coatings
Solution Approach 2:
The patent employs composite optical structures combining transmission gratings with specific substrate materials and coating layers. The grating structure itself acts as a composite element that diffracts light while the substrate provides mechanical support and thermal management, enabling high power handling capability that simple dielectric coatings cannot achieve
2Power
If spectral beam combining techniques are used to combine multiple wavelengths, then beam power is improved, but beam quality may deteriorate
Solution Approach 1:
The patent applies local quality optimization by carefully controlling the diffraction of each wavelength component through the transmission grating. Each wavelength is diffracted at a specific angle according to the grating equation, allowing individual beam quality preservation while achieving overall power combination. The non-Littrow geometry ensures that each wavelength maintains its spatial coherence and beam profile characteristics
3Productivity
If transmission gratings are used in non-Littrow orientation, then combining efficiency is improved and multiple beams can be combined, but device complexity increases
Solution Approach 1:
The patent uses segmentation by dividing the combination of multiple beams into sequential stages using cascaded transmission gratings. Each grating handles a specific subset of wavelengths or beams, making the overall complex task manageable through modular segmentation. This approach maintains high efficiency while organizing the complexity into manageable, interchangeable units
Solution Approach 2:
The transmission grating in non-Littrow orientation serves multiple functions simultaneously: it acts as a wavelength separator, a beam combiner, and a spatial filter. The same grating structure handles both the diffraction of individual beams and the overall combination geometry, reducing the need for additional specialized components and thereby managing complexity through multi-functionality
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 the efficient combination of beams with excellent beam quality, high power handling, and broad spectral bandwidth, overcoming the limitations of existing technologies by achieving high diffraction efficiency and minimizing interference, while also providing a robust and reliable system with a high laser damage threshold.
Implementation Method 1
the transmission grating and/or the system that includes the grating is configured to have only +1 and −1 diffraction orders to produce high efficiency. Two optical beams, which may be monochromatic and/or have same or different wavelengths, can be incident on the transmission grating and diffract into opposite diffraction orders output from the grating.
Data Source
AI summary
A transmission grating optical beam combiner is provided. In some implementations, the beam combiner can include an optically transparent substrate and a transmission grating on the substrate. The transmission grating can be configured to combine and/or superimpose first and second input beams as a single output beam. The first input beam can be incident on the transmission grating at an angle corresponding to one diffraction order of the grating and the second input beam can be incident on the transmission grating at an angle corresponding to another diffraction order of the grating.