Fiber Laser Pulse Width Control for High Average Power
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Solution Overview
Problem
Conventional fibre laser oscillators face challenges in increasing average power at low frequencies due to peak power increases, which can damage the fibre and induce nonlinear optical phenomena like stimulated Raman scattering, making it difficult to perform processes requiring high power, such as deep metal penetration or black marking.
Innovation Solution
A light amplification device with a control unit that adjusts pulse width and excitation light power to increase peak power within a safe threshold, allowing for higher average power output by decreasing repetition frequency and increasing pulse width, while maintaining peak power below damaging levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the repetition frequency is decreased to increase average power, then the average power is improved, but the peak power increases which can damage the fibre
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the pulse width of the laser output in response to changes in repetition frequency. When the repetition frequency decreases, the control unit increases the pulse width to maintain peak power within safe limits while allowing average power to increase. This resolves the contradiction by changing the pulse width parameter to compensate for the effects of frequency changes.
Solution Approach 2:
The patent implements a feedback control mechanism where the control unit monitors the repetition frequency and automatically adjusts the pulse width accordingly. The control unit is configured to increase pulse width when repetition frequency decreases, creating a closed-loop system that maintains peak power within safe thresholds while optimizing average power output. This feedback mechanism resolves the contradiction by continuously adapting parameters based on operating conditions.
2Power
If the peak power is increased to achieve higher average power, then the average power is improved, but nonlinear optical phenomena such as stimulated Raman scattering occur
Solution Approach 1:
The patent changes the pulse width parameter dynamically to prevent nonlinear optical phenomena. By increasing pulse width when repetition frequency decreases, the system maintains peak power below the threshold that triggers stimulated Raman scattering, while still achieving higher average power through the increased duty cycle. This parameter adjustment resolves the contradiction between average power and nonlinear optical effects.
Solution Approach 2:
The control unit is pre-configured with the functional relationship between repetition frequency and pulse width, allowing it to proactively adjust pulse width before nonlinear optical phenomena can occur. The control unit calculates the appropriate pulse width based on the desired repetition frequency, preventing peak power from exceeding safe levels that would trigger Raman scattering. This preliminary action prevents harmful effects before they occur.
3Object-affected harmful factors
If the pulse width is increased to maintain peak power, then the peak power is controlled within safe limits, but the average power may be limited
Solution Approach 1:
The patent applies dynamics by making the pulse width adjustable and dependent on the repetition frequency rather than being fixed. The control unit dynamically modifies pulse width based on the operating conditions, allowing the system to optimize both peak power protection and average power output. This dynamic adjustment resolves the contradiction by adapting parameters in real-time based on operational requirements.
Solution Approach 2:
The system changes the pulse width parameter as a function of repetition frequency to simultaneously achieve safe peak power levels and high average power. By establishing a functional relationship where pulse width increases with decreasing frequency, the system maintains peak power within safe limits while maximizing average power through optimized duty cycle. This parameter change strategy resolves both concerns simultaneously.
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 the fibre laser oscillator to produce higher average power suitable for processes like deep metal penetration and black marking without fibre damage, by controlling peak power and pulse width to prevent nonlinear optical phenomena.
Implementation Method 1
a light amplifying fibre configured to amplify the seed light by the excitation light and output the pulsing amplified light
Data Source
Figure 1
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AI summary
A light amplifier according to an aspect of the present invention includes: a seed light source (2) configured to generate a pulsing seed light; an excitation light source (3, 7) configured to generate excitation light; a light amplifying fiber (1, 9) configured to amplify the seed light by the excitation light and output the amplified light; and a control unit (20) configured to control the seed light source (2) and the excitation light source (3, 7). The control unit (20) has a mode to control the excitation light's power such that as a set value of a pulse width of the amplified light increases, the amplified light's peak energy increases within a threshold value at a minimum set value of the pulse width.