Coherent Beam Combination Phase Locking for High-Power Beam Steering
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Solution Overview
Problem
Existing coherent beam combination (CBC) systems face inefficiencies due to non-linear optical and thermal effects, limited beam steering capabilities, and challenges in maintaining phase coherence among amplified beams, leading to suboptimal power output and control.
Innovation Solution
A CBC system with a laser source, beam broadener, splitter, and focusing optics, coupled with a control unit that includes a phase-locking module and delay compensation, uses a stochastic parallel gradient descent algorithm to optimize phase control and beam steering, achieving high peak intensity and efficient beam recombination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a single laser source is amplified to obtain high power, then power output increases, but non-linear optical effects and thermal effects limit further power increase
Solution Approach 1:
The single laser beam is segmented into N secondary beams using a splitter, each beam is independently amplified through separate channels, and then recombined coherently. This segmentation allows each channel to operate at lower power levels avoiding non-linear effects while achieving high total power through coherent combination.
Solution Approach 2:
Multiple amplified secondary beams are merged through coherent recombination in the focusing optics. The beams are phase-locked and interfered constructively to produce a high-power output beam with peak intensity proportional to N², combining the power of all channels while maintaining beam quality.
2Power
If N channels are individually amplified and recombined to obtain high power output, then power output increases, but maintaining phase coherence and phase-locking among beams requires accurate phase control
Solution Approach 1:
A feedback control system monitors the phase of each channel using photodetectors and adjusts the phase modulators accordingly. The control unit receives signals from detectors and dynamically adjusts phase control signals to maintain phase-locking and constructive interference, ensuring high efficiency coherent combination.
Solution Approach 2:
The system dynamically adjusts phase parameters of each channel through phase modulators controlled by the control unit. By changing phase parameters in real-time based on feedback, the system maintains optimal phase coherence despite environmental disturbances or drift.
3Power
If known CBC systems are used, then beam amplification is achieved, but beam steering is not simple and effective
Solution Approach 1:
The system employs dynamic beam steering by independently controlling the phase and direction of each secondary beam through phase modulators and optical elements in each channel. This allows real-time adjustment of the recombined beam direction without mechanical movement of the entire system, enabling simple and effective beam steering.
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 high peak intensity up to tens of kW, efficient beam steering, and close to theoretical efficiency, with the ability to track and adjust beam position accurately, overcoming limitations of prior systems.
Implementation Method 1
Each channel (20A-20D) comprises an optical amplifier (40)
Implementation Method 2
a phase modulator (42), optically coupled to the optical amplifier (40)
Implementation Method 3
If the amplified beams are coherent one with the other, the amplified beams interfere with each other. In particular, it is desired that the amplified beams interfere constructively with each other.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The coherent beam recombination (CBC) system (1) provides an output recombined beam (2) and comprises: a laser source (3) providing a source beam (8) with linewidth; a beam broadener (5) providing a broadened beam (10) from the source beam; a splitter (7) splitting the broadened beam into a plurality of secondary beams (12A-12D); a plurality of channels (20A-20D) coupled to the splitter. Each channel receives a respective secondary beam (12A-12D) and provides a respective intermediate beam (21A-21D). Each channel has an optical amplifier (40), a phase modulator (42), an optical delay line (44), and an opto-mechanical element (47). The CBC system further comprises an optical sensor (23, 24) that provides a detection signal (INT, IMG) indicative of an intensity of a received optical beam; a focusing optics (17) that receives the intermediate beams (21A-21D), provides the output recombined beam (2) from a first portion of each intermediate beam, and provides a sampled recombined beam (63) to the optical sensor from a second portion (63) of each intermediate beam. The CBC system further comprises a control unit (30) coupled to the optical sensor and the plurality of channels. The control unit comprises a phase-locking module (26) configured to: provide a plurality of phase control signals (u1, u2, u3, u4) to the phase modulators (42); receive the detection signal (INT) from the optical sensor, indicative of an intensity of the sampled recombined beam; calculate a cost function (1) from the detection signal (INT), wherein the cost function is a function of the intensity of the sampled recombined beam; perform an optimization algorithm of the cost function, configured to maximise the intensity of the sample recombined beam; and provide a plurality of updated phase control signals, based on a result of the optimization algorithm.