Laser Oscillator Pulse Modulation to Suppress Raman Scattering
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Solution Overview
Problem
High-power laser oscillators generate stimulated Raman scattering (SRS) during pulse operations, leading to unstable laser beam power and deteriorated beam quality, which affects the processing velocity and quality of thin sheet metal cutting.
Innovation Solution
A laser oscillator and processing machine that employs a pulse generation unit to modulate the driving voltage signal with sub-pulses during high-power periods, alternately repeating high and low states to suppress SRS generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the core diameter of the optical fiber is reduced to achieve high beam quality and high processing velocity, then the beam condensing property is improved, but stimulated Raman scattering is more likely to be generated
Solution Approach 1:
The patent applies periodic action by superimposing sub-pulses on the driving voltage signal during high-power periods. The sub-pulse modulation creates periodic variations in the laser power output, which prevents the continuous high power conditions that lead to SRS accumulation. This periodic modulation allows the system to maintain high average power while avoiding the threshold conditions for SRS generation.
Solution Approach 2:
The patent implements dynamics by making the driving voltage signal adjustable and time-varying. The pulse generation unit dynamically modifies the voltage signal characteristics (superimposing sub-pulses) based on the operating conditions, transforming the static driving signal into a dynamic one that can adapt to prevent SRS while maintaining high power output.
2Object-affected harmful factors
If the effective fiber length is shortened to increase the SRS generation threshold, then stimulated Raman scattering is suppressed, but the feeding fiber length cannot be reduced due to system constraints
Solution Approach 1:
The patent applies parameter changes by modifying the temporal characteristics of the laser power output through sub-pulse modulation. Instead of changing the physical parameter of fiber length, the system changes the operational parameter of power delivery by introducing periodic variations, which effectively raises the SRS threshold without altering the fiber physical dimensions.
3Productivity
If high laser power is used to improve processing capability, then the processing velocity and quality are improved, but stimulated Raman scattering is more likely to be generated causing power instability
Solution Approach 1:
The patent uses periodic action through sub-pulse modulation to create controlled oscillations in the laser power output. This periodic modulation prevents the laser from operating in a continuous high-power state that would lead to SRS-induced instability, while still maintaining high average power for improved processing velocity and 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
Effectively suppresses SRS during pulse operations, maintaining beam quality and enabling high-brightness laser processing with improved cutting and welding capabilities.
Implementation Method 1
When the power of the laser oscillator becomes higher, stimulated Raman scattering, which is one of the non-linear phenomena of the optical fiber, is likely to be generated.
Data Source
AI summary
A pulse generation unit generates a driving voltage signal including a pulse signal. A laser oscillation module oscillates a laser beam by carrying out, based on the driving voltage signal, a pulse oscillating operation. When the power command signal has a voltage command value corresponding to a laser power greater than a predetermined laser power during a high period, the pulse generation unit modulates, in a pulsed manner, a voltage value of the high period of the driving voltage signal so as to alternately repeat, for a preset period of time from a rising time of the high period of the driving voltage signal, a high state in which the voltage value is maintained and a low state in which the voltage value is lowered by a predetermined voltage value without being lowered to a voltage value of a low period of the driving voltage signal.