Low-mode high power fiber combiner with cladding mode absorber
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High power fiber laser systems face challenges in maintaining output quality and power efficiency due to structural defects and unwanted forward and backreflected light, which cause power losses and damage to components.
Innovation Solution
A multi-layer configuration for SM-LM combiners with a cladding mode absorber, featuring three zones with specific refractive index polymers to filter out unwanted light and a filtering splice to prevent high aperture rays from propagating further, along with a downstream component to scatter and direct cladding light to a heat sink.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple single mode fiber laser systems are optically and mechanically coupled together in a combiner to achieve kW power levels, then the output power is improved, but structural defects and power losses occur during fabrication and operation
Solution Approach 1:
The combiner fabrication process is divided into distinct operational stages (alignment, heating, fusing, tapering) with controlled temperature zones. The multi-layer cladding structure is segmented into inner and outer layers with different material properties, allowing each layer to serve specific functions during fabrication and operation, thereby maintaining structural integrity while achieving high power output.
Solution Approach 2:
The fiber cladding is constructed as a composite structure with an inner layer (original cladding material) and an outer layer (different material with specific properties). This composite configuration allows the outer layer to protect against fabrication damage while the inner layer maintains optical performance, resolving the contradiction between achieving kW power levels and maintaining structural reliability.
2Use of energy by moving object
If forward propagating core-guide light is allowed to bleed into cladding at air-quartz interfaces, then power distribution is improved, but thermal loads damage polymeric coating
Solution Approach 1:
The patent converts the potentially harmful thermal load from cladding light into a beneficial heating effect for the polymeric coating. By allowing controlled light bleeding into the cladding and using the resulting thermal energy to heat and cure the coating, the system transforms what would be a damaging factor into a useful process enabler, achieving both power distribution and coating consolidation.
Solution Approach 2:
The polymeric coating undergoes a phase transition from uncured to cured state through thermal heating. The controlled thermal load from cladding light provides the necessary energy for this phase transition, allowing the coating to consolidate and protect the fiber structure without suffering damage, thus resolving the contradiction between power distribution and thermal damage.
3Object-affected harmful factors
If backreflected light is removed from waveguide before propagating back into fiber laser systems, then component protection is improved, but power loss occurs in the removal process
Solution Approach 1:
The polymeric coating serves as an intermediary layer between the cladding and the external environment. It absorbs and manages the backreflected light energy, preventing it from propagating back into the fiber laser systems while minimizing power loss through controlled absorption and thermal conversion. This intermediary structure protects components without significant energy loss.
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 solution effectively minimizes power losses and protects components from thermal deformation, ensuring high quality and reliable kW-level output with minimal damage during fabrication and operation.
Implementation Method 1
The outer layer is made from SiO2 doped with ions of fluorine ("F") and having a relatively low melting temperature
Implementation Method 2
a cladding mode absorber which is operative to efficiently filter out unwanted forward propagating and backreflected cladding light
Implementation Method 3
a filtering splice to prevent high aperture rays from propagating further
Implementation Method 4
a downstream component to scatter and direct cladding light to a heat sink
Implementation Method 5
three zones with specific refractive index polymers to filter out unwanted light
Data Source
Figure 1~3
Figure 4~5
AI summary
A high power fiber laser system is configured with a combiner end fiber spliced to a combiner output fiber. The system further includes a light stripper extending along the combiner end and output fibers and configured with sequentially located zones 'which are provided with respective refractive indices. In a forward propagating direction of light signal, the upstream zone includes polymeric material with the refractive index higher than that of the cladding of the combiner end fiber. This zone is configured to remove the backreflected core guided light bled into the cladding of the combiner through a splice between combiner end and output fibers. The intermediate zone includes polymeric material configured with a refractive index lower than that of the cladding of the combiner output fiber so it can prevent clad guided signal light from decoupling the cladding under the material. The downstream zone is configured with polymeric material having a refractive index lower than that of the cladding of the combiner output fiber. The polymeric material of the downstream zone is impregnated with a plurality of light diffusers scattering high numerical aperture rays of the clad-guided signal light.