Fiber Laser Filter for Reflected Light Damage Suppression
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Solution Overview
Problem
Fiber lasers face internal damage due to reflected light, and existing solutions to mitigate this often result in a decline in output light intensity.
Innovation Solution
A fiber laser configuration that includes a filter allowing only signal light and longer wavelength light to pass through, while blocking light with maximum gain wavelengths, combined with an optical isolator to prevent reflected light from re-entering the rare-earth doped fiber, and a control unit to adjust pumping light intensity based on detected reflected light levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a filter with narrowed wavelength band is used to remove ASE light, then internal damage from reflected light is suppressed, but the intensity of output signal light is declined
Solution Approach 1:
The filter is designed with non-uniform wavelength characteristics: it has high attenuation only in the specific wavelength band where ASE light causes damage (shorter wavelengths), while maintaining high transmission in the signal light wavelength range and longer wavelength bands. This localized filtering approach suppresses harmful ASE light while preserving the intensity of useful signal light.
Solution Approach 2:
The filter's transmission characteristics are optimized by changing its wavelength-dependent parameters. The filter allows transmission of signal light at its specific wavelength and light at longer wavelengths, while blocking only the problematic ASE wavelength band. This parameter-based selection enables differentiation between harmful and useful light components.
2Reliability
If a filter with narrowed wavelength band is used to remove ASE light, then reflected light amplification is prevented, but the degree of output light intensity decline increases with higher intensity output attempts
Solution Approach 1:
The filter provides localized protection by attenuating only the specific wavelength band where ASE light is generated and causes reflected light amplification. By targeting only this narrow problematic band while maintaining high transmission for signal light and longer wavelengths, the filter prevents reflected light amplification without limiting the fiber laser's ability to produce high intensity output light.
Solution Approach 2:
The filter applies partial action by removing only the necessary portion of light (ASE light in the specific wavelength band) without excessively filtering the useful signal light. This partial removal approach is sufficient to prevent reflected light amplification while maintaining high productivity for the desired output.
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 internal damage from reflected light while maintaining the intensity of the output light, ensuring reliable operation of the fiber laser.
Implementation Method 1
a light emitting unit including a pumping light source configured to emit pumping light, and a rare-earth doped fiber on which the pumping light is incident, and to which a rare-earth element that is to be pumped by the pumping light is doped, the light emitting unit being configured to amplify pulsed signal light in the rare-earth doped fiber
Implementation Method 2
The filter does not allow transmission of light in at least a part of a wavelength band, including the wavelength with which a gain is maximized in the rare-earth doped fiber, and allows transmission of light with the same wavelength as the signal light and light in a wavelength band on a side with a longer wavelength than the wavelength of the signal light
Data Source
AI summary
A fiber laser includes a light emitting unit that amplifies pulsed signal light in a rare-earth doped fiber and emits output light, and a filter arranged in an optical path of the output light emitted from the light emitting unit. The signal light is light having a longer wavelength than a wavelength with which a gain is maximized in a rare-earth doped fiber within a gain wavelength band of the rare-earth doped fiber. The filter does not allow transmission of light in at least a part of the wavelength band that includes the wavelength with which the gain is maximized in the rare-earth doped fiber, and allows transmission of light having the same wavelength as the signal light and light in a wavelength band on a longer wavelength side than the wavelength of the signal light.