Amplification Optical Fiber Radial Index Profile for Beam Quality
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Solution Overview
Problem
Existing amplification optical fibers struggle to emit light with high power and improved beam quality, as expanding the doping area of active elements can amplify higher-order modes, reducing beam quality.
Innovation Solution
The amplification optical fiber design includes a core with a first and second core portion, where the refractive index of the first core portion is higher than the clad, and the second core portion has an even higher refractive index than the first, with the active element doped at a higher concentration in areas where the LP01 mode power exceeds the LP11 mode power, ensuring the formula ∫0∞n(r)×{I01(r)−I11(r)}rdr>0 is satisfied, thereby amplifying the LP01 mode more than the LP11 mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the doping area of active elements is expanded to increase output power, then the power of emitted light is increased, but the beam quality is reduced due to amplification of higher-order modes
Solution Approach 1:
The patent applies local quality by creating a core with non-uniform refractive index distribution, where the refractive index varies radially to selectively guide different modes. The core has a higher refractive index at the center and gradually decreases toward the periphery, which confines the LP01 mode more effectively than the LP11 mode, enabling selective amplification in specific regions to maintain beam quality while increasing power
Solution Approach 2:
The patent changes the refractive index parameter radially across the core to control mode propagation characteristics. By adjusting the refractive index profile (higher at center, lower at periphery), the fiber optimizes the confinement of fundamental modes while allowing higher-order modes to propagate with less amplification, thus maintaining beam quality at higher power levels
2Power
If a larger core diameter is used to allow high power propagation, then the output power is increased, but the beam quality deteriorates due to higher-order mode content
Solution Approach 1:
The patent implements local quality through a radially varying refractive index profile within the core, where the refractive index is highest at the center and decreases toward the periphery. This local variation in optical properties enables selective mode guidance, confining the LP01 mode more tightly while allowing LP11 modes to extend into regions with lower refractive index, thus achieving high power capacity with maintained beam quality
Solution Approach 2:
The patent addresses the two-dimensional trade-off between core size and beam quality by introducing a radial dimension for refractive index variation. Instead of uniformly increasing core diameter, the solution varies the refractive index along the radial dimension, creating an optimized mode confinement profile that enables high power propagation while maintaining beam 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 configuration enhances the beam quality of the output light by selectively amplifying the LP01 mode while suppressing the LP11 mode, allowing for higher power emission with reduced nonlinear optical effects and improved focusing capabilities.
Implementation Method 1
an active element that stimulates to emit light of the predetermined wavelength is doped
Implementation Method 2
a refractive index of the first core portion is higher than that of the clad, a refractive index of the second core portion is higher than that of the first core portion
Data Source
AI summary
The refractive index of the first core portion 11a is higher than that of a clad 12, and the refractive index of the second core portion 11b is higher than that of the first core portion 11a. When light of the LP01 mode and light of the LP11 mode are standardized by power, in the core 11, an active element that stimulates to emit light of the predetermined wavelength is doped at a higher concentration in at least a part of an area where power of light of the LP01 mode is larger than that of light of the LP11 mode than at least a part of an area where the power of light of the LP11 mode is larger than that of light of the LP01 mode.