Coherent Laser Beam Combining with Dynamic Phase Control
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Solution Overview
Problem
High-power laser systems face challenges in maintaining and repairing due to stringent requirements for balancing amplifier chains, particularly when using seed lasers with shorter coherence lengths, as the coherence length decreases with increased linewidth, leading to difficulties in balancing path lengths and increasing the risk of stimulated Brillouin scattering.
Innovation Solution
An apparatus for combining laser radiation that includes a seed laser, splitter, amplifier chains, reference amplifier chain, detection means, demodulator means, and phase control means, where the output power is at least 50 W, the seed laser bandwidth is at least 1 GHz, and the path length difference between amplifier chains is less than the coherence length, allowing for dynamic balancing and phase control using optical fibre heating and quantum defect mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the linewidth of the seed laser is increased to raise the SBS threshold, then the power level at which SBS becomes noticeable increases, but the coherence length decreases and the balancing requirement becomes more difficult
Solution Approach 1:
The patent implements dynamic path length balancing using active feedback control. Phase detectors monitor the coherence of combined beams from multiple amplifier chains, and piezoelectric actuators dynamically adjust the optical path lengths to maintain balancing within the coherence length, even when using seed lasers with shorter coherence lengths and broader linewidths.
Solution Approach 2:
The system employs feedback control where phase detectors continuously monitor the interference pattern of combined laser beams, and the detected phase information is used to drive piezoelectric actuators that adjust optical path lengths, creating a closed-loop control system that maintains path length balancing dynamically.
2Power
If the coherence length of the seed laser is shortened to allow broader linewidth operation, then the SBS threshold increases, but the path length balancing becomes more difficult especially during maintenance and replacement
Solution Approach 1:
The dynamic feedback control system allows the laser system to automatically rebalance after amplifier replacement. The phase detectors and piezoelectric actuators adapt to new path lengths in real-time, eliminating the need for manual precision balancing during maintenance and enabling the use of shorter coherence length seed lasers.
Solution Approach 2:
The system performs self-balancing through automatic feedback control. When amplifiers are replaced or conditions change, the phase detection and piezoelectric adjustment system automatically restores optimal path length balancing without requiring external intervention or precise manual adjustment.
3Productivity
If the output power of each amplifier chain is increased to achieve higher total power, then the system efficiency improves, but the risk of stimulated Brillouin scattering increases
Solution Approach 1:
The patent broadens the linewidth of the seed laser (increasing its bandwidth), which directly increases the SBS threshold power level. This parameter change allows each amplifier chain to operate at higher power levels before SBS becomes problematic, improving overall system efficiency while controlling harmful nonlinear effects.
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 solution enables easier maintenance and repair of high-power laser systems by allowing the use of seed lasers with shorter coherence lengths, reducing the risk of stimulated Brillouin scattering, and achieving coherent combination with improved beam quality and increased power output.
Implementation Method 1
a seed laser (2) having a bandwidth of at least 1 GHz
Implementation Method 2
each amplifier chain (4) comprising at least one optical amplifier (11)
Implementation Method 3
the path length difference (14) between each amplifier chain (4) and the reference amplifier chain (7) is less than the coherence length (10) of the seed laser (2)
Implementation Method 4
SBS is characterized by a frequency shift between the forward propagating pump wave and the backward travelling wave
Data Source
AI summary
Apparatus for combining laser radiation (1) 5 which apparatus comprises a seed laser (2), a splitter (3), a plurality of amplifier chains (4), a reference amplifier chain (7), detection means (5). demodulator means (6), and phase control means (12), wherein each of the amplifier chains (4) comprises at least one optical amplifier (11), optical radiation (17) emitted from the seed laser (2) is split into the plurality of amplifier chains (4) by the splitter (3). amplified by the plurality of amplifier chains (4), interfered, detected by the detection means (5), demodulated by the demodulator means (6), and a signal (27) indicative of path length imbalance (14) fed back to the phase control means (12), and wherein the apparatus is characterized in that the output power emitted by each amplifier chain (4) is at least 50 W, the bandwidth (8) of the seed laser (2) is at least 1 GHz, and the path length difference (14) between each amplifier chain (4) and the reference amplifier chain (7) is less than the coherence length (10) of the seed laser (2).