Dual-Zone Coupling Lens for Fiber Laser Pump Focus Alignment
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Solution Overview
Problem
High-power fiber lasers and amplifiers face challenges in efficiently coupling pump and laser radiation due to excessive dispersion and residual axial focus point differences, especially at significantly different wavelengths, leading to increased coating losses, larger beam diameters, and limited integration possibilities, which are detrimental in compact and robust designs required for military and industrial applications.
Innovation Solution
A dual-zone coupling lens is designed with an inner zone adapted to the laser wavelength and an outer zone adapted to the pump wavelength, optimizing focal planes to minimize power losses and achieve simultaneous coupling of both radiations using a single lens, exploiting the numerical aperture difference between the pump and laser beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If free-beam laser sections are coupled into fibre sections, then high peak power can be achieved, but high pulse energies lead to nonlinear effects and damage
Solution Approach 1:
The laser system is divided into separate free-beam and fibre sections that are coupled together. The free-beam section generates high peak power pulses, while the fibre section delivers the energy with controlled parameters. This segmentation allows each section to operate in its optimal regime without suffering from the drawbacks of the other.
Solution Approach 2:
A coupling element acts as an intermediary between the free-beam laser section and the fibre section. This coupling element transfers the laser beam from free-space to the fibre core while managing the transition of optical parameters, enabling high peak power generation without directly exposing the fibre to conditions that would cause damage.
2Power
If beam parameters are transformed through coupling, then high peak power is achieved, but the process is complex and costly
Solution Approach 1:
The coupling element serves as a specialized intermediary device that performs the beam parameter transformation in a controlled manner. By using a dedicated coupling element designed for this specific purpose, the complexity is contained in a single component rather than distributed across multiple complex systems.
Solution Approach 2:
The coupling element is designed to transform beam parameters (such as mode field diameter, numerical aperture, and wavefront curvature) in a controlled manner. By systematically managing these parameter changes, the coupling process achieves high peak power transmission while keeping the device design manageable.
3Power
If high pulse energies are used, then high peak power is generated, but nonlinear effects and damage occur
Solution Approach 1:
The system separates the high energy generation function (in free-beam section) from the high intensity transmission function (in fibre section). This segmentation allows the fibre to be exposed to high peak power only during brief coupling intervals, avoiding cumulative damage from continuous high pulse energy exposure.
Solution Approach 2:
The coupling element acts as a protective intermediary that manages the transfer of high pulse energies. It controls the coupling conditions to ensure that the fibre receives the necessary peak power while minimizing exposure to harmful nonlinear effects and damage-inducing 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 optical arrangement enhances efficiency and power handling capabilities, enabling compact and robust designs suitable for high-power fiber lasers in military and industrial applications by minimizing focal plane differences and beam diameters, thus improving integration and reducing complexity.
Implementation Method 1
a free-beam laser section (101) arranged to generate laser beams
Implementation Method 2
a fibre laser or fibre amplifier section (102) arranged to amplify the laser beams
Implementation Method 3
a coupling element (103) arranged to couple free-beam laser sections into fibre sections
Data Source
Figure 1~3
Figure 4
AI summary
The present invention relates to an optical arrangement comprising a fibre laser (1) or fibre amplifier (2), which has at least one active fibre (3) with a fibre core and at least one fibre jacket and a coupling lens (4), which is arranged at a distance from a first fibre end of the active fibre (3) and can be coupled into the fibre jacket by means of the pump radiation (5) via the first fibre end. The coupling lens (4) has a circular inner zone (4a) and an annular outer zone (4b), which are designed so that a focal plane of collimated radiation of the pump wavelength, incident on the outer zone (4b), is closer to a focal plane of collimated radiation of the laser wavelength incident on the inner zone (4a) than in a conventional embodiment of a lens, which has just one focal plane in the entire lens region for one wavelength. An increased efficiency of the fibre laser or fibre amplifier and higher pump and output powers can be achieved with the proposed optical arrangement. The entire arrangement can be can be realised in a compact design by using just one individual coupling lens.