Spectrally Multiplexed Diode Pump Modules for Fiber Laser Brightness
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Solution Overview
Problem
The power scaling of fiber lasers is limited by nonlinear processes and thermal effects, and existing methods fail to effectively address these limitations, hindering further power scaling and improving beam quality.
Innovation Solution
The method involves generating pump beams at multiple wavelengths corresponding to ytterbium absorption peaks, combining these beams using wavelength and polarization multiplexing, and directing them into a gain fiber to produce a brighter optical output, thereby increasing the SRS threshold and maintaining beam quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If single-wavelength pump sources are used, then the system is simple, but the brightness and power scaling are limited
Solution Approach 1:
The patent combines multiple diode laser sources operating at different wavelengths (900-930 nm and 970-980 nm) into a single pump beam that simultaneously excites ytterbium-doped fiber at multiple absorption peaks, thereby increasing overall pump brightness without proportionally increasing system complexity
Solution Approach 2:
The pump source is segmented into multiple wavelength components that target different absorption peaks of the ytterbium-doped gain medium, allowing each wavelength to contribute independently to the overall pumping efficiency and brightness
2Power
If pump power is increased to scale up laser output, then power scaling is achieved, but nonlinear processes and thermal effects worsen
Solution Approach 1:
The patent changes the spectral parameters of the pump source by incorporating multiple wavelengths that match different absorption peaks of ytterbium, improving pump absorption efficiency and reducing the total pump power required, thereby mitigating thermal effects and nonlinear processes
Solution Approach 2:
The patent converts the typically harmful thermal effects into a benefit by using multiple wavelengths to more efficiently couple pump power into the gain medium, reducing wasted energy and improving overall system efficiency
3Productivity
If multiple wavelengths are combined, then brightness and power scaling improve, but the system complexity increases
Solution Approach 1:
The patent employs optical components such as dichroic mirrors and fiber combiners that serve multiple functions: wavelength separation, beam combining, and mode matching, thereby reducing overall system complexity despite the multi-wavelength approach
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 allows for the generation of high-power continuous-wave fiber laser outputs exceeding 5 kW without significant stimulated Raman scattering, with improved beam quality and increased brightness, enabling more efficient power scaling.
Implementation Method 1
generating one or more pump beams from respective diode lasers at a first wavelength, generating one or more pump beams from respective diode lasers at a second wavelength
Implementation Method 2
combining at least one of the one or more pump beams at the first wavelength with at least one of the one or more pump beams at the second wavelength to form at least one combined pump beam
Implementation Method 3
a first polarization multiplexer situated to receive and combine a first subset of the first plurality of laser beams having a first polarization state and a second subset of the first plurality of laser beams having a second polarization state orthogonal to the first polarization state
Implementation Method 4
focusing optics situated to receive and focus the combined laser beams
Implementation Method 5
the gain fiber includes a ytterbium-doped core, and the first wavelength corresponds to a ytterbium absorption peak or band associated with the wavelength range of 900 nm to 930 nm, and the second wavelength corresponds to a ytterbium absorption peak or band associated with the wavelength range of 970 nm to 980 nm
Data Source
Figure 1A~1D
Figure 2~3
Figure 4A~4B
AI summary
A method of spectrally multiplexing diode pump modules to increase brightness includes generating one or more pump beams from respective diode lasers at a first wavelength in a diode laser package, generating one or more pump beams from respective diode lasers at a second wavelength different from the first wavelength in the diode laser package, wavelength combining at least one of the pump beams at the first wavelength with at least one of the pump beams at the second wavelength to form one or more combined pump beams, and receiving the combined pump beams in a pump fiber coupled to the diode laser package. Laser systems can include multi- wavelength pump modules and a gain fiber having a core actively doped so as to have an absorption spectrum corresponding to the multiple wavelength, the gain fiber situated to receive the pump light and to produce an output beam at an output wavelength.