Variable Beam Characteristics Fiber for Optical Power Density Control
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Solution Overview
Problem
Fiber lasers and fiber-coupled lasers face limitations in maintaining optimal optical beam characteristics, such as spot size and power density, due to stimulated Raman scattering (SRS) effects, which restrict the length and core diameter of delivery fibers, especially at higher optical powers.
Innovation Solution
The use of a variable beam characteristics (VBC) fiber system, which includes a first length of fiber with a specific refractive index profile and a second length with multiple confinement regions, allows for adjustment and control of optical power density by perturbing the beam and confining it within these regions to avoid SRS effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the length of delivery fiber is increased to enable longer power delivery, then the ability to deliver optical power over distance is improved, but stimulated Raman scattering (SRS) effects occur that degrade beam quality and limit further power increases
Solution Approach 1:
The patent applies dynamic control of beam characteristics by using a variable beam characteristics (VBC) fiber system that can adjust its effective core diameter and refractive index profile in real-time. This allows the fiber to dynamically adapt its confinement properties to maintain optimal beam quality at different power levels and lengths, preventing SRS effects from degrading beam quality during power delivery.
Solution Approach 2:
The patent changes key physical parameters of the fiber system, specifically the effective core diameter and refractive index profile, to optimize power delivery. By adjusting these parameters, the system can increase fiber length while maintaining beam quality, as the modified parameters reduce the impact of SRS effects that normally limit length and power.
2Power
If the core diameter of delivery fiber is increased to accommodate higher optical power, then the power handling capability is improved, but the spot size and beam characteristics at output deteriorate
Solution Approach 1:
The patent implements local quality by creating multiple confinement regions within the fiber with different refractive indices and sizes. Each region is optimized for specific power levels and beam characteristics, allowing the system to maintain optimal spot size and beam shape even when handling high optical power. The different regions provide localized optimization rather than a uniform approach.
Solution Approach 2:
The VBC fiber system dynamically adjusts which confinement region is active based on the input power level, allowing the effective core diameter to change with power. This dynamic adaptation ensures that beam shape and spot size remain optimal across a wide range of power levels, preventing deterioration that would occur with a fixed core diameter.
3Length of moving object
If the fiber length is extended to reach remote targets, then the delivery distance capability is improved, but non-linear optical effects such as SRS increase and limit further extension
Solution Approach 1:
The patent changes the refractive index profile and effective core diameter parameters of the fiber to reduce the intensity of optical effects that cause SRS. By optimizing these parameters, the system can extend delivery distance while keeping non-linear effects below threshold levels, allowing fiber length to increase without being limited by harmful optical effects.
4Productivity
If the optical power is increased to improve processing capability, then the productivity is improved, but the risk of SRS effects and beam quality degradation increases
Solution Approach 1:
The VBC fiber system provides dynamic control that allows the fiber to adapt its confinement properties to the instantaneous power level. This enables the system to operate at high power levels for improved processing capability while automatically adjusting parameters to maintain beam quality and prevent SRS effects, resolving the contradiction between productivity and reliability.
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 approach enables the maintenance of adjusted optical beam characteristics, reducing the risk of SRS and allowing for longer fiber lengths and higher optical powers without non-linear effects, thereby optimizing beam quality and power delivery for various applications.
Implementation Method 1
a first length of fiber having a first refractive index profile (RIP), the first RIP enabling, in response to an applied perturbation, modification of the optical beam to form an adjusted optical beam
Implementation Method 2
a second length of fiber having an input end coupled to the output end of the first length of fiber, the second length of fiber formed with multiple confinement regions defining a second RIP that is different from the first RIP, the multiple confinement regions arranged to confine at least a portion of the adjusted optical beam
Data Source
AI summary
An optical power control system includes a laser source to provide an optical beam, a variable beam characteristics (VBC) fiber, and a controller operatively coupled to the VBC fiber and configured to control, in response to information indicating change in optical power of the optical beam, different states of perturbation so as to control optical power density.