Coherent Laser Array Phase Control via Interferometric Feedback
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Solution Overview
Problem
High-power fibre lasers face limitations in power generation due to small core diameters, leading to non-linear effects and damage thresholds, particularly when scaling to a large number of fibre amplifiers, where wavelength recombination becomes impractical for spectral control.
Innovation Solution
A high-power laser source employing a collective coherent phase-control technique, utilizing a coherent source to interfere with fibre amplifier outputs, generating an interferogram for phase detection and compensation via a spatial modulator, enabling phase modulation of each fibre amplifier to achieve coherent addition and increased power output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the number of fibre amplifiers is increased to generate higher power, then the output power increases, but non-linear effects and damage thresholds appear due to small core diameter
Solution Approach 1:
The system segments the high-power generation task across multiple fibre amplifiers (N amplifiers) rather than relying on a single amplifier. Each amplifier operates at lower power levels within safe thresholds, while the collective array achieves high total power through coherent combination, resolving the contradiction between power scaling and damage thresholds
Solution Approach 2:
The patent merges the outputs of N fibre amplifiers through coherent combination using phase control. The individual beams are combined constructively to achieve total power equal to N times the power of a single amplifier, while maintaining reliability by keeping each individual amplifier operating below damage thresholds
2Power
If wavelength multiplexing is used to combine fibre amplifier outputs, then power scaling is achieved, but spectral control becomes impractical for large numbers of amplifiers
Solution Approach 1:
The patent replaces the mechanical/optical complexity of wavelength multiplexing systems with an electronic phase control system. Instead of using complex wavelength division multiplexing hardware for N amplifiers, the system uses electronic phase modulators and interferometric detection to achieve coherent combination, dramatically simplifying spectral control while maintaining power scaling capability
Solution Approach 2:
The system changes the control parameter from wavelength multiplexing to phase modulation. By controlling the phase of each amplifier's output rather than relying on wavelength separation, the system achieves scalable power combination with simplified spectral control, especially for large N where wavelength multiplexing becomes impractical
3Ease of operation
If individual unit phase modulators are coupled to each fibre amplifier, then coherent phase control is achieved, but device complexity increases significantly for large N
Solution Approach 1:
The patent introduces an intermediary interferometric detection system that measures the relative phases of all N amplifiers simultaneously. This intermediary measurement system allows centralized phase control through a single spatial light modulator, avoiding the need for complex distributed control of N individual phase modulators and significantly reducing overall system complexity
Solution Approach 2:
The system implements feedback control by detecting the interferogram to determine relative phases, then using this information to adjust the phase modulator settings. This feedback loop enables automatic coherent phase control of all N amplifiers through a unified control mechanism, reducing operational complexity compared to manual control of individual modulators
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 allows for high-power emission and brightness enhancement, compatible with large arrays of fibre amplifiers, achieving N or N2 times the power of an elementary amplifier, while maintaining high spatial resolution and image rate compatibility.
Implementation Method 1
means for making the coherent wave interfere with the optical waves output by the fibre amplifiers, and generating an interferogram consisting of an array of fringes
Implementation Method 2
processing/display means for processing the detected phase law and for displaying it on the spatial modulator, said spatial modulator being positioned so as to be able to be read by the signal wave and thus generate a phase-modulated signal wave
Data Source
AI summary
The invention relates to a laser device comprising a number of fiber amplifiers (3) delivering a number of optical waves, which is supplied by an oscillator (1) that delivers a signal wave, characterized in that said device comprises:a coherent source (4) emitting a coherent wave at a wavelength approximately equal to that of the signal wave and the propagation direction of which is inclined to the propagation direction of the optical waves output by the fiber amplifiers;means for making the coherent wave interfere with the optical waves output by the fiber amplifiers, and generating an interferogram consisting of an array of fringes;interferogram detection means (7), the relative positions of the fringes transcribing an inter-fiber phase law;a spatial phase modulator (2); andprocessing/display means (6) for processing the detected phase law and for displaying it on the spatial modulator, said spatial modulator being positioned so as to be able to be read by the signal wave and thus generate a phase-modulated signal wave selectively at each of the fiber amplifiers, compensating for the phase shifts induced by said fiber amplifiers.