Spectral Beam Combiner Wavelength Feedback for Beam Alignment
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Solution Overview
Problem
Fiber laser amplifier systems face challenges in maintaining uniform phase and beam quality due to wavelength drifts and pointing direction changes over time, especially as the number of channels increases, requiring precise wavelength locking to prevent degradation in combined output beam quality.
Innovation Solution
A fiber laser amplifier system with multiple seed beam sources, each generating a seed beam at a unique wavelength, uses beam collimating optics and a spectral beam combining grating to align amplified beams, along with a detector assembly and feedback components to control wavelength and maintain alignment, ensuring all beams propagate in the same direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the number of laser channels is increased to achieve higher output power, then the total power increases, but the wavelength spacing between channels decreases requiring higher precision wavelength locking
Solution Approach 1:
The patent combines multiple individual wavelength lockers into a single shared wavelength locker that serves all laser channels. This is achieved by combining the output beams from all channels and using a single Fabry-Perot interferometer to monitor and control the wavelength of each channel, thereby reducing component count while maintaining the required precision for closely spaced wavelengths.
Solution Approach 2:
The single wavelength locker performs multiple functions by simultaneously monitoring and controlling the wavelength of all laser channels. The system uses a wavelength demultiplexer to distribute the combined beam signal to individual control channels, allowing one device to serve multiple purposes and maintain precision across all channels despite reduced spacing.
2Device complexity
If conventional Fabry-Perot based wavelength lockers are used, then the system is simple, but achieving wavelength locking precision within 1 GHz is difficult
Solution Approach 1:
The patent implements a feedback control system where the Fabry-Perot interferometer continuously monitors the wavelength of each laser channel and feeds this information back to control mechanisms (such as piezoelectric actuators or temperature control) that adjust the laser wavelength. This closed-loop feedback ensures wavelength locking precision within 1 GHz while maintaining reasonable system complexity.
3Ease of operation
If wavelength drift is not corrected, then the system operates simply, but the pointing direction of beams changes resulting in reduced beam quality
Solution Approach 1:
The system uses feedback control where wavelength drift is continuously monitored by the Fabry-Perot interferometer and corrected in real-time through feedback to the laser control mechanisms. This maintains beam quality stability despite thermal or mechanical changes in the system.
Solution Approach 2:
The wavelength locking system is self-correcting, automatically detecting and compensating for wavelength drift without requiring external intervention. The system monitors its own performance and makes real-time adjustments to maintain optimal beam quality.
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 effectively stabilizes beam wavelengths and maintains beam alignment, enhancing the quality of the combined output beam by precisely controlling seed beam wavelengths and compensating for thermal and mechanical changes, thereby improving the power and focus of the far-field beam.
Implementation Method 1
a spectral beam combining (SBC) grating responsive to the collimated uncombined beams and spatially combining the collimated uncombined beams at the different wavelengths so that all of the separate amplified beams in the collimated uncombined beams are directed in the same direction as an output beam
Data Source
Figure 1~2
Figure 3~4
AI summary
A fiber amplifier system including a plurality of seed beam sources each generating a seed beam at a different wavelength and a plurality of fiber amplifiers that amplify the seed beams. The system also includes a spectral beam combining (SBC) grating that spatially combines the amplified beams and directs them in the same direction as an output beam, and a first fiber sampler and a second fiber sampler that generate a first fiber sample beam having a first intensity and a second fiber sample beam having a second intensity. The system further includes a configuration of optical and electrical feedback components that determine a difference between the first intensity and the second intensity and use the difference to control the wavelength of all of the seed beams so that all of the amplified beams are spatially aligned and propagating in the same direction in the output beam.