Coherent Beam Combination Phase Correction via Target In-the-Loop Interferometry
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Solution Overview
Problem
Existing coherent beam combination (CBC) systems face challenges in accurately synchronizing phase offsets between multiple beams, particularly in free-space laser systems affected by atmospheric turbulence, with stochastic approaches converging too slowly for large numbers of beams.
Innovation Solution
A deterministic method using Target In-the-Loop Interferometry (TILI) and interferometric techniques to measure and correct phase offsets by modulating each beam's phase at multiple frequencies, calculating phase offsets relative to the sum of all other beams, and rapidly adjusting phases to achieve coherent combination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a stochastic approach is used for phase correction in CBC systems, then the system can handle atmospheric turbulence, but the convergence speed is too slow for large numbers of beams
Solution Approach 1:
The patent replaces the stochastic (random trial-and-error) phase correction approach with a deterministic interferometric measurement system. By using target-in-the-loop interferometry, the system directly measures phase offsets through optical interference patterns and calculates precise correction values, eliminating the slow random search process while maintaining adaptability to atmospheric conditions
Solution Approach 2:
The patent implements a feedback mechanism where the phase offsets are continuously measured through interferometric detection of reflected target radiation, and correction values are fed back to the beam phase modulators. This closed-loop system rapidly converges to optimal phase synchronization by using real-time measurement data rather than stochastic exploration
2Power
If the number of beams to be combined is increased for power scaling, then the laser output power increases, but the difficulty of achieving phase offset correction is greatly compounded
Solution Approach 1:
The patent segments the phase correction problem by using individual phase modulators for each beam and measuring phase offsets independently through interferometric techniques. Each beam's phase can be corrected separately based on its measured offset, making the scaling to large numbers of beams manageable rather than requiring simultaneous coordination of all beams
Solution Approach 2:
The patent introduces a target-in-the-loop interferometric measurement system as an intermediary between the multiple beams and the phase correction control. This intermediary directly measures the phase relationships and provides quantitative feedback, simplifying the control complexity even as the number of beams increases for power scaling
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
Enables rapid and accurate phase correction, even under dynamic conditions, enhancing coherent beam combination energy delivery and adaptability to atmospheric turbulence.
Implementation Method 1
the current phase of each transmitted beam is modulated at a modulation frequency
Implementation Method 2
A detector is provided for detecting variations in reflected intensity from the target
Data Source
Figure 1~2
Figure 3~4
Figure 5A~6
AI summary
A coherent beam combination (CBC) system (10) includes an array of beam sources (12a, 12b and 12c) generating coherent beams directed towards a target (T). The phase modulators (14a, 14b and 14c) allow adjustment of relative phase offsets of the beams. A detector (16) monitors an intensity of the radiation impinging on an area of the target (T). A controller (18) receives the intensity parameter and controls a phase adjustment of the beams according to a deterministic (i.e., quantitative) measurement of a phase offset of each beam relative to a representative phase of the sum of all the other beams. This is achieved by using interferometric techniques, referred to herein as Target In-the-Loop Interferometry (TILI).