Coherent Beam Combination Using Target In-the-Loop Interferometry
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Solution Overview
Problem
Coherent beam combination systems face challenges in accurately correcting phase offsets between multiple beams, especially in free-space laser systems affected by atmospheric turbulence, as the number of beams increases, leading to rapid variations in diffractive properties.
Innovation Solution
A method and system that monitor intensity parameters at a target, actuate phase modulators to modulate beam phases between multiple states, identify variations, and calculate phase offsets relative to a representative phase, allowing for real-time phase correction using Target In-the-Loop Interferometry and adaptive optics to synchronize beams effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the number of beams to be combined is increased to achieve higher power scaling, then the power output is improved, but the difficulty and complexity of phase offset correction increases significantly
Solution Approach 1:
The patent transforms the complex multi-beam phase correction problem into a series of simpler two-beam interference measurements by modulating beam phases and detecting intensity variations. This parameter transformation approach allows scalable correction for any number of beams without proportionally increasing system complexity.
Solution Approach 2:
The system implements real-time feedback by continuously monitoring intensity parameters, calculating phase offsets, and adjusting phase modulators accordingly. This closed-loop feedback mechanism enables dynamic correction of phase offsets even as the number of beams increases, maintaining correction effectiveness through iterative optimization.
2Reliability
If rapid phase correction is implemented to compensate for atmospheric turbulence variations, then the beam synchronization is improved, but the system response time requirements and measurement precision demands increase
Solution Approach 1:
The patent employs periodic phase modulation of beams at distinct frequencies, allowing the system to encode phase information in time-varying intensity patterns. This periodic modulation approach enables rapid extraction of phase offset data through frequency-domain analysis, achieving both fast response and high precision measurements.
Solution Approach 2:
The system performs preliminary phase modulation and intensity measurement before final phase correction is applied. By pre-modulating beams with known phase patterns and measuring the resulting intensity variations, the system can calculate accurate phase offsets in advance, enabling proactive synchronization rather than reactive correction.
3Measurement precision
If phase modulation is performed at multiple frequencies simultaneously for multiple beams, then the measurement accuracy is improved, but the device complexity and control requirements increase
Solution Approach 1:
The patent segments the multi-beam phase measurement problem into individual two-beam interference measurements. Each beam's phase offset is determined separately by comparing it with a reference beam through intensity modulation and detection, rather than attempting to measure all beams simultaneously in a single complex measurement.
Solution Approach 2:
The system uses intensity variations as an intermediary to indirectly measure phase offsets. Instead of directly measuring phase differences between beams, the patent modulates beam phases and detects the resulting intensity changes at the target, using intensity as a mediator that encodes phase information in a measurable form.
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 rapid and accurate phase correction of multiple beams, enhancing coherent beam combination by minimizing phase differences and improving energy delivery to a target, even under conditions of moderate to high atmospheric turbulence.
Implementation Method 1
actuating the corresponding phase modulator to modulate a current phase of the transmitted beam between at least three phase states
Implementation Method 2
identifying variations in the intensity parameter resulting from the modulation of the current phase of each transmitted beam relative to the sum of all the other beams
Data Source
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).