Fiber Laser Reflected Light Resistance via Wavelength Filtering
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Solution Overview
Problem
High power density MO-PA fiber lasers are prone to damage from reflection light, and existing solutions like isolators are expensive and inefficient, particularly when dealing with high power outputs, as they generate heat and fail to adequately prevent parasitic oscillation across all wavelengths.
Innovation Solution
Incorporating a wavelength conversion portion between the master oscillator and power amplifier, along with wavelength filters before and after the conversion, to differentiate and block reflection light wavelengths from the original pulse light, thereby preventing damage without the need for expensive isolators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an isolator is used to protect optical components from reflection light, then the reliability of the fiber laser is improved, but the cost increases significantly and heat generation occurs at high power outputs
Solution Approach 1:
The patent extracts the harmful reflection light from the system by introducing a wavelength filter that selectively removes reflected light at specific wavelengths while allowing the main laser wavelength to pass through. This eliminates the need for expensive isolators by targeting only the harmful component rather than blocking all light.
Solution Approach 2:
The patent introduces a wavelength filter as an intermediary component between the optical components and the reflection light. This filter acts as a mediator that allows the main laser beam to pass while blocking the harmful reflected light, providing protection without the cost and heat issues of isolators.
2Reliability
If an isolator is used to prevent parasitic oscillation, then the reliability is improved, but it fails to adequately prevent parasitic oscillation across all wavelengths and generates heat
Solution Approach 1:
The patent applies local quality by using a wavelength filter with specific transmission characteristics that targets only the problematic reflected light wavelengths while maintaining high transmission for the main laser wavelength. This localized filtering approach suppresses parasitic oscillation where needed without affecting the main beam or generating excessive heat.
Solution Approach 2:
The patent changes the wavelength parameter of the light being filtered, using a filter that blocks reflected light at specific wavelengths while allowing the main laser wavelength to pass. This parameter-based selection enables selective suppression of parasitic oscillation without the heat generation problems of broad-spectrum isolators.
3Ease of manufacture
If a wavelength filter is used to block reflection light, then the cost is reduced and heat generation is minimized, but additional components are added to the system
Solution Approach 1:
The wavelength filter serves multiple functions simultaneously: it blocks reflected light to prevent damage, suppresses parasitic oscillation across different wavelengths, and maintains high transmission for the main laser beam. This multi-functionality reduces the need for multiple separate components like isolators, ultimately simplifying the system despite adding a filter element.
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 effectively blocks reflection light without using costly isolators, reduces heat generation, and suppresses parasitic oscillation, enhancing the reliability and cost-effectiveness of the fiber laser by allowing wavelength conversion regardless of the pulse light wavelength and increasing the power of pulse light amplified by the power amplifier.
Implementation Method 1
a wavelength filter which transmits only wavelength components of pulse light emitted from the master oscillator
Implementation Method 2
a wavelength conversion portion which converts a wavelength of pulse light emitted from the master oscillator to another wavelength
Data Source
Figure 1~3
Figure 4~5
Figure 6~7
AI summary
An MO-PA fiber laser having a master oscillator; and a first power amplifier which uses as a gain medium, a rare earth-doped optical fiber which is connected to a later stage of the master oscillator, wherein the MO-PA fiber laser has a wavelength conversion portion between the master oscillator and the power amplifier, and has a wavelength filter between the wavelength conversion portion and the master oscillator which only allows wavelength components of pulse light emitted from the master oscillator to pass, thereby making it possible to prevent breakage to a fiber laser which is caused by reflection light without using high-cost optical components.