Fibre Laser Damage Protection via Capillary Termination
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Solution Overview
Problem
Fibre lasers are vulnerable to damage from reflected radiation during material processing, particularly with highly reflective materials like copper, which can cause the 'optical fuse effect, leading to destruction of the delivery fibre and pump diodes due to uncontrolled plasma propagation.
Innovation Solution
A fibre laser system with enhanced damage resistance features, including a capillary termination to reduce power intensity, multiple cladding layers to confine stray radiation, cladding mode strippers, and power monitors to detect and prevent damage, along with an annular pump combiner to isolate pump radiation from the core, ensuring safe operation and protection of critical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If pump radiation is applied to the optical gain medium to generate laser beam, then laser output power is improved, but the system becomes vulnerable to damage from reflected radiation
Solution Approach 1:
The patent introduces intermediary components between the pump diodes and the optical gain medium, specifically isolating cladding layers and protective elements, that mediate the interaction between pump radiation and the laser medium while protecting against reflected radiation damage
2Productivity
If laser beam intensity is increased to improve material processing capability, then productivity is improved, but the optical fuse effect becomes more likely to occur
Solution Approach 1:
The patent implements protective measures before the optical fuse effect can occur by introducing damage-resistant designs and protective cladding structures that cushion against the harmful effects of high intensity radiation before they can cause fibre destruction
3Device complexity
If reflected radiation is allowed to return to pump diodes, then device complexity is reduced, but the pump diodes will be damaged
Solution Approach 1:
The patent extracts and removes reflected radiation from the system by introducing isolation mechanisms and protective structures that take out the harmful reflected beams before they can reach and damage the pump diodes
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 system effectively mitigates damage from errant radiation, preventing destruction of the fibre laser components and allowing for simple restoration of operation by controlling power intensity and isolating stray radiation, thus enhancing the robustness and reliability of fibre laser systems during material processing.
Implementation Method 1
a fibre termination, at an output end, which is arranged to enable expansion of a laser beam, before it is launched, to thereby reduce power intensity at the point of launch
Implementation Method 2
a capillary mounted at the output end and having a face, at its end closest to the active gain medium, which is angled to have an angle greater than 0° but less than 90° to the axial direction of the fibre
Implementation Method 3
multiple cladding layers to confine stray radiation
Implementation Method 4
a core of an optical fibre is doped with a rare earth element to become an active gain medium and pump radiation is applied via a cladding layer
Implementation Method 5
The defect in the optical fibre creates a region of high absorption which can raise the core to above 1000 C and a plasma is created in the core. This plasma will propagate towards the source of radiation, destroying the core of the delivery fibre at a subsonic velocity
Data Source
AI summary
A fibre laser system is disclosed comprising an optical fibre, a part of which is doped with a rare earth to form an optical gain medium; at least one laser diode; means for applying pump radiation from the laser diode to the optical gain medium and for generating a laser beam and delivery fibre means for delivering a laser beam to a workpiece, wherein the fibre laser is provided with at least one means for protecting one or more components from damage caused by errant radiation. Several different means of protection are disclosed.