Optical Fiber Cladding Scattering Centers for Laser Radiation Extraction
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Solution Overview
Problem
High-power laser radiation often enters the cladding region of optical fibers, leading to radiation absorption and damage, as well as compromised beam quality due to disturbances in total reflection at fiber bends or splices, which affects processing quality and the integrity of the fiber.
Innovation Solution
Incorporating scattering centers in the second outer fiber cladding, particularly in the capillary-free longitudinal section, to scatter and extract laser radiation from the inner fiber cladding, while maintaining the radiation-guiding characteristics of the fiber core, using techniques such as introducing air-filled bubbles or micro-crystals, or generating scattering centers through ultra-short laser pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a flexible protective sheath with lower refractive index is used to protect the optical fiber, then the fiber is protected mechanically, but laser radiation entering the cladding region is absorbed and heated the protective sheath causing damage
Solution Approach 1:
The patent extracts the harmful laser radiation from the cladding region by introducing a longitudinal section with modified capillary structure that allows selective coupling of cladding modes to radiation modes, extracting the radiation before it reaches the protective sheath and causing heating damage
Solution Approach 2:
The patent introduces an intermediary longitudinal section with specific capillary structure that acts as a mediator between the cladding region and the protective sheath, enabling controlled radiation extraction through mode coupling while protecting the sheath from harmful heating
2Use of energy by moving object
If total internal reflection is used to guide laser radiation in the fiber core, then radiation transmission is efficient, but disturbances at fiber bends or splices cause radiation to escape into the protective sheath
Solution Approach 1:
The patent applies preliminary action by introducing a longitudinal section with modified capillary structure before radiation can escape at bends or splices, enabling pre-extraction of potentially harmful cladding radiation through controlled mode coupling
3Illumination intensity
If capillary-threaded quartz glass cladding is used to reduce effective refractive index, then beam quality is improved, but laser radiation can still enter the cladding region and be conveyed outside the fiber core
Solution Approach 1:
The patent applies local quality by creating a longitudinal section with specifically modified capillary structure (different from the rest of the fiber) that enables selective extraction of cladding radiation through mode coupling, while maintaining the beneficial capillary-threaded structure elsewhere for 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 solution effectively reduces radiation-related damage and maintains beam quality by selectively extracting radiation from the fiber core, preventing absorption and heating issues, and allowing for precise control of radiation power measurement and coupling.
Implementation Method 1
The core carries laser radiation up to a maximum acceptance angle by means of total internal reflection. The cladding is not used for light transmission, but provides the lower refractive index necessary for the total internal reflection.
Implementation Method 2
The second outer fiber cladding has scattering centers, at least in the region of the capillary-free longitudinal section, for scattering the laser radiation emerging from the inner fiber cladding along the capillary-free longitudinal section.
Data Source
AI summary
An optical fiber is designed to transmit high-power laser radiation. The optical fiber includes a fiber core, and an inner fiber cladding surrounding the fiber core, where the inner fiber cladding is configured to carry the laser radiation in the fiber core. The optical fiber also includes a first outer fiber cladding surrounding the inner fiber cladding. The first outer fiber cladding has a capillary-free longitudinal section and has a smaller refractive index than the refractive index of the inner fiber cladding. The optical fiber includes an outermost fiber cladding surrounding the first outer fiber cladding. The outermost fiber cladding has scattering centers that surround the capillary-free longitudinal section, where the scattering centers scatter laser radiation emerging from the inner fiber cladding through the first outer fiber cladding along the capillary-free section.