Optical Fiber Taper Cladding Mode Stripper for High Power Laser Coating Protection
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Solution Overview
Problem
High power fibre lasers face reliability issues due to polymer coatings overheating when exposed to high numerical aperture pump radiation, and existing solutions involving liquids or polymers are complex, expensive, and thermally unreliable.
Innovation Solution
A glass taper with a cladding mode stripper is used to attenuate higher angle rays, reducing damage to the polymer coating on the output fibre by adjusting the factor β, which is less than 1.0, and positioning the stripper along the taper to fine-tune the attenuation, thereby minimizing heating and maintaining optical power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polymer coating is used on the output fibre to guide pump radiation, then the fibre can be protected and light can be guided, but the polymer coating overheats and damages when exposed to high numerical aperture pump radiation
Solution Approach 1:
The invention extracts and removes the harmful high numerical aperture rays from the optical system by positioning the cladding mode stripper at a specific diameter along the taper where these rays can be stripped from the cladding and directed away from the polymer coating, thereby protecting the coating from overheating
Solution Approach 2:
The cladding mode stripper acts as an intermediary component between the taper and the output fibre, selectively removing harmful high NA rays while allowing useful lower NA rays to pass through to the polymer coating, thus mediating the interaction between light and the coating
2Power
If liquid cooling and refractive index control are used to remove unwanted light, then high power pump radiation can be handled, but the system becomes complex and expensive
Solution Approach 1:
The invention extracts the harmful function of liquid cooling and complex refractive index control systems by replacing them with a simple cladding mode stripper positioned at a critical diameter on the taper, which passively removes unwanted high NA rays through mode stripping without requiring active cooling or complex material properties
Solution Approach 2:
The cladding mode stripper enables the system to self-regulate and protect itself from overheating through its geometric design and position on the taper, eliminating the need for external liquid cooling systems and complex refractive index management
3Power
If higher power pump radiation is used to increase laser output, then power-scaling is achieved, but the polymer coating absorbs excessive energy and degrades
Solution Approach 1:
The invention converts the harmful effect of high numerical aperture rays, which would normally cause polymer coating degradation, into a beneficial filtering mechanism where the cladding mode stripper selectively removes these harmful rays while preserving the useful lower NA rays needed for laser operation, thus enabling higher power operation without coating damage
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 or eliminates damage to the polymer coating, enhancing the reliability and power-handling capabilities of high power fibre lasers and amplifiers, particularly those above 1 kW, by using an all-glass cladding mode stripper that does not contain polymers, fluids, or gels, thus preventing thermal degradation.
Implementation Method 1
the taper comprises a cladding mode stripper located at a diameter DCMS equal to a fraction... such that higher angle rays propagating along the taper towards the output optical fibre are attenuated
Implementation Method 2
the taper comprises a waveguide having a glass outer cladding... which waveguide is defined by a numerical aperture NAT
Data Source
AI summary
An apparatus for combining optical radiation, wherein the apparatus comprises a bundle of input optical fibers formed of glass, a taper, and an output optical fiber, wherein the taper is fused to the output optical fiber; and the apparatus comprises at least one cladding mode stripper to strip out higher order modes that would otherwise degrade a polymer coating on at least one of the input optical fibers and the output optical fiber.