Ball Lens Expanded-Beam Coupling for Sub-Micron Fiber Alignment
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Solution Overview
Problem
Existing optical coupling solutions face challenges in achieving sub-micron alignment accuracy between optical fibers and micro-lenses, leading to significant optical signal losses due to misalignment, particularly in co-packaged optics systems.
Innovation Solution
The use of ball lenses in expanded beam fiber array units (EB-FAUs) with semiconductor substrates, such as silicon, enables precise alignment through high-precision patterning processes, allowing for sub-micron accuracy and simplified assembly by leveraging features like V-grooves and symmetric ball lenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If expanded beam lenses are used to increase misalignment tolerance, then alignment sensitivity is improved, but manufacturing precision requirements for sub-micron alignment between micro-lenses and fiber centers worsen
Solution Approach 1:
The patent employs ball lenses with spherical geometry instead of traditional aspheric or cylindrical lenses. The spherical shape provides inherent rotational symmetry that simplifies alignment requirements while maintaining beam expansion functionality. The ball lens is positioned in a recessed cavity with precise depth control, allowing the spherical surface to naturally focus and expand beams with reduced sensitivity to angular misalignment.
Solution Approach 2:
The ball lens is nested within a precisely engineered recessed cavity in the substrate. This nesting structure provides mechanical support and positional reference, with the cavity depth and diameter precisely controlled to position the ball lens center at the required sub-micron accuracy relative to fiber centers. The nested configuration protects the lens while maintaining optical performance.
2Measurement precision
If traditional alignment methods are used for connecting optical fibers with silicon waveguides, then alignment accuracy can be achieved, but device complexity and assembly difficulty increase
Solution Approach 1:
The patent integrates the ball lens directly into the substrate with the fiber array, merging the optical coupling function with the mechanical support structure. The recessed cavity is formed in the same substrate that holds the fibers, combining alignment references and optical elements into a single integrated component, thereby simplifying assembly while maintaining sub-micron alignment accuracy.
Solution Approach 2:
The ball lens configuration with its spherical symmetry provides self-aligning properties. The rotational symmetry of the ball lens means that small angular deviations do not significantly impact optical performance, providing a degree of self-tolerance to alignment errors. This reduces the need for complex active alignment procedures during assembly.
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 significantly reduces optical signal losses to approximately 0.1 dB or lower, enhancing optical coupling efficiency and alignment precision in optical systems.
Implementation Method 1
The expanding beam lens expands the optical beam in order to increase tolerance to misalignment
Data Source
AI summary
Embodiments disclosed herein comprise an apparatus with a substrate with a first surface, and a second surface that is recessed from the first surface. In an embodiment, the second surface is adjacent to an edge of the substrate. In an embodiment, a hole is in the second surface, and a groove is in the first surface. In an embodiment, a centerline of the groove passes over the hole.