Monolithic Phased Array Beam Shaping for High Fill Factor CBC
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Solution Overview
Problem
Fiber laser amplifier systems face challenges in combining beams to achieve a uniform phase over the beam diameter, leading to clipping losses and reduced fill factor, which affects the ability to focus the combined beam to a small spot effectively, especially in applications like directed energy weapons.
Innovation Solution
A coherently combined fiber laser amplifier system with a beam shaper array assembly that includes spaced apart tiled beam shaper arrays, transforming round Gaussian beams into high fill factor beams with minimal clipping losses, using beam shaper arrays to alter the spatial phase distribution and intensity profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple fiber laser amplifiers are combined to increase output power, then the power of the laser amplifier is improved, but the beam quality and phase uniformity deteriorate
Solution Approach 1:
The system divides the laser beam into multiple separate fiber amplifier channels, each processing a portion of the total power. These segmented beams are then coherently combined through precise phase control to achieve high power output while maintaining beam quality and phase uniformity across the combined beam profile.
2Device complexity
If beam combining is performed without beam shaping, then the device complexity is reduced, but the fill factor and energy efficiency deteriorate due to clipping losses
Solution Approach 1:
Beam shaping optics are integrated into each fiber amplifier channel before the beams are combined. This preliminary shaping of individual beams ensures optimal spatial profiles that maximize the fill factor during coherent combination, thereby minimizing clipping losses and improving energy efficiency before the beams are merged.
3Reliability
If the beam diameter is increased to reduce diffraction effects, then the beam quality is improved, but the focusing capability to a small spot deteriorates
Solution Approach 1:
The system dynamically controls the phase and amplitude parameters of individual fiber beams through electronic feedback and phase modulation. By adjusting these parameters, the system maintains a larger effective beam diameter for reduced diffraction while simultaneously enabling precise focusing to a small spot through coherent control, effectively decoupling these two opposing requirements.
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 system achieves a nearly 100% fill factor with uniform intensity and phase across the emitting aperture, enabling high-speed beam steering and compensation for atmospheric aberrations, improving beam quality and focusing capabilities.
Implementation Method 1
beam shaper arrays that each convert a round Gaussian or other low fill factor beam to a high fill factor beam
Data Source
Figure 1
Figure 2~3
Figure 4A~4D
AI summary
A coherently beam combining (CBC) fiber laser amplifier system including beam shaper array assembly and a beam source that provides a plurality of beams having a low fill factor profile. The assembly includes an input beam shaper array having a plurality of input cells positioned adjacent to each other that are shaped to cause the beam to expand as it propagates away from the input array to be converted from the low fill factor profile to a high fill factor profile and cause the profile to taper to a lower value at a perimeter of each input array cell. The assembly further includes an output beam shaper array having a plurality of output cells positioned adjacent to each other that are shaped to cause the beam to stop expanding so that the output array provides a plurality of adjacent beams with minimal overlap and a minimal gap between the beams.