Fiber Laser Pulse Control Prevents High-Peak Damage
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Solution Overview
Problem
The use of high-peak pulses in pulsed fiber laser processing can damage the core of the oscillation optical fiber and adversely affect processing performance, and maintaining a constant laser oscillation state increases power consumption and safety risks.
Innovation Solution
A fiber laser processing method that controls the LD drive current in a power feedback control mode to gradually raise the output of the fiber laser beam from a low level to a desired level, preventing the occurrence of abnormal high-peak pulses and halting laser oscillation during non-processing periods, thereby enhancing safety and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the LD drive current rising rate is enhanced to increase repetition frequency of the fiber laser beam, then productivity is improved, but abnormal high-peak pulses occur at the rising edge which can damage the oscillation optical fiber core
Solution Approach 1:
The patent applies preliminary action by introducing a pre-pulse before the main processing pulse. This pre-pulse gradually excites the oscillation optical fiber core, bringing it to a stable oscillation state before the main pulse arrives. By doing so, when the main pulse is applied, the fiber is already prepared and can handle the high energy without producing abnormal high-peak pulses that would damage the core. This resolves the contradiction by enabling high repetition frequency operation while protecting the fiber core through preparatory excitation.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting the LD drive current waveform parameters. Specifically, it shapes the drive current to include a pre-pulse portion with controlled amplitude and duration, followed by the main pulse. The pre-pulse parameters are optimized to gradually build up oscillation in the fiber core, while the main pulse parameters are set for effective processing. This parameter control prevents abnormal high-peak pulses while maintaining high repetition frequency, thus resolving the technical contradiction between productivity and fiber core protection.
2Reliability
If a constant base current is applied to maintain the fiber laser in a low-power oscillation state during waiting period, then safety is improved by preventing high-peak pulses, but power consumption increases and LD life is shortened
Solution Approach 1:
The patent applies periodic action by using pulsed operation mode instead of continuous base current. During waiting periods when no processing is required, the system completely shuts off the LD drive current, achieving zero power consumption. When processing is needed, precisely shaped pulses (including pre-pulse and main pulse) are applied only at those moments. This periodic on-off operation eliminates the need for continuous base current while still preventing abnormal high-peak pulses, as the pre-pulse ensures the fiber is properly prepared before each main pulse. This resolves the contradiction between safety and power consumption by making the protective mechanism event-driven rather than continuous.
3Loss of time
If the LD drive current is rapidly increased to reach desired output level, then time efficiency is improved, but abnormal high-peak pulses occur which adversely affect processing quality
Solution Approach 1:
The patent applies preliminary action by incorporating a pre-pulse that begins the excitation process before the main processing pulse. This pre-pulse rapidly brings the oscillation optical fiber core to a near-ready state, and then the main pulse completes the excitation to the desired output level. This two-stage approach significantly reduces the total time to reach desired output compared to gradual ramping, while the controlled pre-pulse ensures no abnormal high-peak pulses are generated. Thus, the contradiction between time efficiency and processing quality is resolved by using preliminary excitation followed by a controlled main pulse.
Solution Approach 2:
The patent employs parameter changes by optimizing the temporal and amplitude parameters of the drive current waveform. The pre-pulse is configured with specific amplitude (lower than main pulse) and duration (optimized to bring fiber to near-ready state), while the main pulse has higher amplitude and shorter duration (optimized for processing). These parameter optimizations enable rapid transition to desired output level without generating harmful high-peak pulses, thereby resolving the contradiction between speed 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
This approach effectively prevents high-peak pulses at the rising edge of the pulsed fiber laser beam, ensuring the stability of laser processing quality, safety, and reducing power consumption by maintaining a stable output and halting laser oscillation during idle periods.
Implementation Method 1
an LD end face excitation mode is employed by using a laser diode (LD) for an excitation light source and focusing and making the LD light (excitation light) incident on the core end face
Implementation Method 2
the core of the optical fiber is optically excited to reciprocate an oscillation light beam with a predetermined wavelength output from the end face of the core in the axial direction between the optical resonant mirrors a number of times for resonance and amplification
Implementation Method 3
an optical lens is disposed between the fiber end face and the optical resonant mirror to converge (focus) the oscillation light beam reflected by the optical resonant mirror with the optical lens to return the light beam to the core end face
Data Source
AI summary
A fiber laser processing apparatus controls a LD drive current ILD in a power feedback control mode (FIG. 3E) such that output of a fiber laser beam FB rises substantially from zero or a value around zero to a preceding level having no substantial effect on laser processing and arrives at a desired level (PA) for the laser processing from a preceding level PB after a first time period (preceding pulse width TB) has elapsed (time point t2 of FIGS. 3A to 3F) from the start of the rising to the preceding level (time point t1 of FIGS. 3A to 3F), and this may effectively prevent occurrence of a high-peak pulse HP at the rising edge of the fiber laser beam FB (FIG. 3F).