Fiber-Coupled Diode Laser Beam Circularization for Higher Brightness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fiber-coupled laser diode packages face challenges in achieving optimal brightness due to the rectangular beam shape and mismatch between the laser diode beams' angular and physical divergence spaces and the circular space of the fiber, limiting the number of emitter beams that can be coupled into the fiber.
Innovation Solution
The use of beam shaping optics, including afocal fast and slow axis telescopes with variable focal lengths and collimators, to circularize the ensemble image and numerical aperture spaces of laser diode beams at the coupling plane, allowing for different magnifications and displacements along the fast and slow axes, thereby optimizing the filling of the fiber's circular space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple single-emitter diode lasers are stacked in the fast axis to achieve power scaling, then power and brightness are improved, but the rectangular beam shape and mismatch between beam divergence spaces and fiber circular space limit further brightness improvement
Solution Approach 1:
The patent applies local quality by implementing beam-specific optical paths with individual fast axis collimators and telescopes for each diode emitter. Each beam receives customized optical treatment with different magnifications and displacements tailored to its specific characteristics, allowing optimal adaptation of each beam to the fiber's circular acceptance space while maintaining high power from multiple stacked emitters
Solution Approach 2:
The patent employs parameter changes by varying the focal lengths of fast axis collimators and telescopes for different beams in the stack. This allows each beam to be independently optimized with different magnification factors, transforming the uniform rectangular beam parameters into a distributed set of parameters that collectively fill the fiber's circular NA space more efficiently
2Power
If beam shaping optics with different focal lengths are used to circularize ensemble image space, then brightness and power coupling efficiency are improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the beam shaping function into discrete modular components: individual fast axis collimators for each emitter, separate telescope assemblies with adjustable magnifications, and staged optical paths. This modular segmentation allows the complex beam circularization function to be achieved through multiple simple, independent optical elements rather than a single complex system
Solution Approach 2:
The patent introduces intermediary optical elements (fast axis collimators and telescopes) that mediate between the laser diode emitters and the fiber coupling interface. These intermediaries transform and adapt the beams step-by-step, first collimating individual beams and then applying magnification/displacement transformations, making the overall system more manageable and aligning beam parameters with fiber requirements
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 enhances brightness by allowing more single emitter beams to be coupled into the fiber, achieving up to 57% power and brightness improvement by efficiently utilizing the available numerical aperture and physical space of the fiber.
Implementation Method 1
beam shaping optics include a plurality of fast axis collimators with different focal lengths configured to produce different corresponding fast axis magnifications for the respectively received beams, and a plurality of slow axis collimators with different focal lengths configured to produce different corresponding slow axis magnifications
Implementation Method 2
afocal fast axis telescope configured to receive the laser diode beams as fast-axis and slow-axis collimated beams with the beam axes parallel to each other and stacked along a common fast axis to define a plurality of initial beam displacements relative to an optical axis of the afocal fast axis telescope, and to compress the laser diode beams along the common fast axis
Data Source
AI summary
Apparatus include a plurality of laser diodes configured to emit respective laser diode beams having perpendicular fast and slow beam divergence axes mutually perpendicular to respective beam axes, and beam shaping optics configured to receive the laser diode beams and to circularize an ensemble image space and NA space of the laser diode beams at an ensemble coupling plane. In selected examples, beam shaping optics include variable fast axis telescopes configured to provide variable fast axis magnification and beam displacement.