Fiber Laser Polarization Control Without PM Fiber Splicing
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Solution Overview
Problem
Fiber-lasers delivering unpolarized radiation require complex and costly polarization-maintaining fibers to achieve plane-polarized operation, which is necessary for frequency-converting near-infrared radiation to cut materials like silicon or copper, and the splicing of these fibers is difficult.
Innovation Solution
A fiber-laser configuration using a non-polarization-maintaining gain-fiber with a polarizer and a waveplate to select and maintain a single linear polarization state, allowing for the delivery of linearly-polarized radiation without the need for polarization-maintaining fibers, and enabling frequency-conversion in optically nonlinear crystals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If polarization-maintaining fiber is used to achieve plane-polarized radiation, then the polarization quality is improved, but the cost and device complexity increase
Solution Approach 1:
The invention extracts the polarization-maintaining function from the fiber itself and relocates it to a separate optical element (waveplate or polarizing beam splitter) in the resonator. This allows the gain fiber to be simple non-polarization-maintaining fiber while still achieving plane-polarized output through the external polarization-selective element.
Solution Approach 2:
A waveplate or polarizing beam splitter is introduced as an intermediary element between the gain fiber and the output coupling. This intermediary component performs the polarization selection function, allowing the fiber itself to remain simple while achieving the desired polarization state at the output.
2Manufacturing precision
If polarization-maintaining fiber is used to achieve plane-polarized radiation, then the polarization quality is improved, but the splicing difficulty increases
Solution Approach 1:
The invention extracts the polarization-maintaining function from the fiber itself and relocates it to a separate optical element (waveplate or polarizing beam splitter) in the resonator. This allows the gain fiber to be simple non-polarization-maintaining fiber while still achieving plane-polarized output through the external polarization-selective element.
3Use of energy by moving object
If fundamental-wavelength radiation is used for cutting, then the laser efficiency is improved, but the ability to cut transparent or reflective materials deteriorates
Solution Approach 1:
The invention changes the wavelength parameter of the laser radiation through frequency conversion (e.g., second harmonic generation) while maintaining the plane-polarized state. This allows the system to convert from efficient NIR fundamental wavelength to shorter wavelengths (e.g., visible range) that are better suited for cutting transparent or reflective materials like silicon and copper.
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 configuration simplifies the production and maintenance of fiber-lasers while achieving plane-polarized radiation, enabling efficient frequency-conversion for materials transparent or reflective to near-infrared radiation, reducing costs and splicing complexities.
Implementation Method 1
a waveplate arranged to rotate the plane of polarization of radiation circulating in the resonator by 90 degrees
Implementation Method 2
a polarizer arranged to transmit radiation having polarization in a plane
Implementation Method 3
the fundamental-wavelength radiation be frequency-converted in an optically nonlinear crystal to provide shorter-wavelength radiation
Data Source
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AI summary
A fiber-laser includes a gain-fiber in a laser-resonator. A polarizer is located in the laser-resonator at an end thereof, causing the output of the fiber-laser to be linearly polarized. A wavelength-selective element is also included in the laser-resonator for selecting an output wavelength of the fiber-laser from within a gain-bandwidth of the gain-fiber.