Side-Pumped Fiber Laser Reflective Coating Protection
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Solution Overview
Problem
High power fiber laser systems with side-pumping arrangements face issues with undesirable dispersion of high pump power at the ends of the coupling region, leading to heat generation and potential burning of the reflective coating, resulting in quick destruction of the gain block.
Innovation Solution
A protective layer with a refractive index smaller than the core of the multimode passive fiber is applied to the ends of the pump fiber, sandwiched between the doped fiber and the reflective coating, minimizing direct contact with high pump power and preventing burning. This layer is made of materials like SiF or polymers and is applied during the manufacturing process using preforms with alternating radial regions to shield the ends of the reflective cladding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If pump light is launched into the doped fiber through the coupling region, then signal light is amplified, but heat is generated at the end portions of the coupling region causing burning of the reflective coating
Solution Approach 1:
A protective layer with lower refractive index than the pump fiber core is introduced as an intermediary between the pump fiber and reflective coating at the coupling region ends. This protective layer has lower absorption characteristics, preventing pump light from directly contacting and heating the reflective coating, thereby eliminating the harmful thermal effect while maintaining the amplification function
Solution Approach 2:
The protective layer is applied specifically at the end portions of the coupling region where heat generation occurs, rather than uniformly throughout. This localized application addresses the specific problem area (where pump light dispersion causes overheating) without affecting the overall coupling efficiency or amplification performance of the gain block
2Productivity
If the reflective coating is exposed to high pump power at the ends of the coupling region, then pump light can be launched, but the reflective coating burns and the gain block is destroyed
Solution Approach 1:
The protective layer serves as a mediator that allows pump light to be launched into the doped fiber through the coupling region while simultaneously protecting the reflective coating from direct exposure to high pump power. The layer transmits sufficient pump light for effective amplification while blocking the harmful concentrated power at the ends
Solution Approach 2:
The protective layer is applied in advance to the pump fiber at the coupling region ends before the gain block is assembled or before operation begins. This pre-protection measures prevents the burning of reflective coating before it can occur, ensuring long-term reliability of the gain block under high pump power conditions
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
The protective layer effectively prevents the burning of the reflective coating, ensuring the stability and longevity of the high power fiber laser system by reducing direct exposure to high pump powers, thus extending the lifespan of the gain block.
Implementation Method 1
The protective layer is configured with a refractive index smaller than that one of the core of the MM passive fiber
Implementation Method 2
pump light, launched by passive pump delivery fiber 12, starts propagating into doped fiber 16 through end portions A of coupling region 14. As pump light propagates along coupling region 14, its major part is gradually absorbed by gain medium of a core 20 of doped fiber 16 so as to amplify signal light
Data Source
AI summary
A twin fiber laser arrangement is configured with active and passive fibers supporting respective signal and pump lights and a reflective coating surrounding the fibers along a section of the arrangement. The passive fiber has regions covered by respective protective layer and coating-free regions alternating with the layer covered regions, wherein the reflective coating is configured to overlap the protective layer which shields the end of the reflective coating from high power pump light.