Fiber Beam Shaper Array for High Fill Factor Beam Combining
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Solution Overview
Problem
Fiber laser amplifier systems face challenges in achieving high fill factors and low clipping losses when combining beams from multiple fiber amplifiers, leading to inefficiencies in beam focusing and beam quality, particularly in directed energy applications where high power and precise beam control are required.
Innovation Solution
The system employs a beam shaper array assembly that includes tiled beam shaper arrays to transform round Gaussian beams into square flat-top beams, achieving nearly 100% fill factor with minimal gaps and overlap, allowing for precise phase control and beam steering without physical deformation of optics, using commercially available fiber-coupled waveguide electro-optic modulators for rapid actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If round Gaussian beams are combined directly from multiple fiber amplifiers, then the beam combining process is simple, but the fill factor is low and clipping losses are high
Solution Approach 1:
The patent transforms the beam profile parameter from round Gaussian to square flat-top using beam shapers. This parameter change allows the beams to pack more efficiently in a grid pattern, achieving near 100% fill factor and minimizing clipping losses at the aperture edges.
Solution Approach 2:
The patent applies beam shapers to individual beams in the array, transforming each beam's local intensity distribution from Gaussian to flat-top. This local transformation enables each beam to contribute uniformly to the combined beam, maximizing the fill factor across the entire aperture.
2Reliability
If traditional deformable mirrors are used for beam steering and aberration compensation, then physical wavefront control is achieved, but the actuation speed is limited to acoustic-class speeds
Solution Approach 1:
The patent replaces the mechanical deformable mirror system with an electro-optic modulator system. Instead of physically deforming a mirror surface, the system uses electro-optic phase modulation to achieve wavefront control. This substitution enables GHz-class actuation speeds, far exceeding the acoustic-class speeds of traditional DMs.
Solution Approach 2:
The patent introduces electro-optic modulators as intermediary devices between the laser sources and the beam combining optics. These modulators impose phase corrections on individual beams before combination, achieving the same wavefront control function as a deformable mirror but with electronic actuation speeds.
3Loss of energy
If beam shapers are added to transform Gaussian beams to flat-top beams, then fill factor increases to nearly 100%, but the device complexity increases
Solution Approach 1:
The patent divides the beam shaping function into individual beam shapers, each processing a single Gaussian beam from one fiber amplifier. This segmentation allows for modular design and independent optimization of each beam channel, making the overall system more manageable despite the increased number of components.
Solution Approach 2:
The patent employs identical beam shaper designs for all channels in the array. This universality simplifies manufacturing and alignment, as the same optical component is replicated across all beam channels. The standardized design reduces the effective complexity by allowing mass production and pre-characterization of the beam shaper units.
Data Source
AI summary
A system for fabricating an optical element. The system includes means for welding an array of fibers to the optical element, means for measuring an angle error and a position error of each fiber, means for calculating a correction for each fiber for the angle error and the position error and means for correcting the angle and position of each fiber using the calculated corrections.