Optical Interface Assembly Using Multimode Interference Lens
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Solution Overview
Problem
The efficient transmission of optical signals between optical components is hindered by diffraction losses due to gaps between waveguides, which are difficult to eliminate due to manufacturing inaccuracies and material limitations, especially in indium phosphide compounds where lens-based adapters are costly and cumbersome to fabricate.
Innovation Solution
The use of a multimode interference (MMI) lens assembly or reflective lensing region with carefully designed refractive indices and dimensions to focus the fundamental mode of light from a source waveguide into a receiving waveguide, effectively reducing diffraction losses and increasing transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If waveguides are brought into sub-micron proximity to reduce diffraction losses, then power transfer efficiency is improved, but manufacturing feasibility deteriorates due to surface perturbations, non-uniformities in manufacturing tolerances, mechanical alignment inaccuracies, and interposing glue
Solution Approach 1:
The patent introduces an intermediary optical element (lens or mode transforming adapter) between the two waveguides. This intermediary collects the diffracted light from the source waveguide and focuses or transforms it into the receiving waveguide, thereby mediating the optical coupling without requiring sub-micron proximity between the waveguides themselves. This resolves the contradiction by maintaining manufacturing feasibility while achieving efficient power transfer through the intermediary optical component.
Solution Approach 2:
The patent replaces the mechanical alignment system (requiring sub-micron precision mechanical positioning of waveguides) with an optical system (lens or mode transforming adapter) that provides optical focusing and mode matching. This substitution eliminates the need for extremely precise mechanical alignment and gap control, thereby resolving the contradiction between power transfer efficiency and manufacturing precision.
2Loss of energy
If lens-based adapters are used to collect and focus diffracted light, then power transfer efficiency is improved, but fabrication cost and complexity increase significantly in indium phosphide compounds
Solution Approach 1:
The patent changes the material parameter from indium phosphide (which is costly and cumbersome to etch and regrow) to silicon-based materials or other materials that are more easily fabricated using standard CMOS or MEMS processes. This parameter change maintains the optical focusing function while dramatically reducing fabrication cost and complexity, thereby resolving the contradiction between power transfer efficiency and ease of manufacture.
Solution Approach 2:
The patent implements the optical focusing function locally within the packaged device using integrated lens structures or mode transforming adapters fabricated in the same material system as the waveguides. This local implementation eliminates the need for complex multi-material fabrication processes and repeated etching and regrowth operations, thereby reducing fabrication cost and complexity while maintaining efficient power transfer.
3Manufacturing precision
If larger gaps are allowed between waveguides to accommodate manufacturing tolerances, then manufacturing feasibility is improved, but diffraction losses increase
Solution Approach 1:
The patent introduces an intermediary optical element (lens or mode transforming adapter) between the two waveguides. This intermediary collects the diffracted light from the source waveguide and focuses or transforms it into the receiving waveguide, thereby mediating the optical coupling without requiring sub-micron proximity between the waveguides themselves. This resolves the contradiction by maintaining manufacturing feasibility while achieving efficient power transfer through the intermediary optical component.
Solution Approach 2:
The patent employs mode transforming adapters that can dynamically adapt to varying gap conditions and alignment tolerances. The mode transforming adapter is designed to provide robust coupling over a range of gap widths and alignment conditions, thereby providing dynamic adaptability that resolves the contradiction between manufacturing tolerance and diffraction loss.
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 provides a high-efficiency optical interface with over 80% power transfer, being tolerant of manufacturing variances and gap widths, and is more cost-effective than conventional methods, particularly in challenging material systems like indium phosphide.
Implementation Method 1
The first waveguide is configured such that the optical signal undergoes multimode interference to focus the fundamental mode at the end portion of the second waveguide
Implementation Method 2
a cladding layer surrounding the first and second waveguides
Data Source
AI summary
An optical device includes a first waveguide having an end portion configured to receive an optical signal, the optical signal having a fundamental mode; a second waveguide having an end portion spaced from the end portion of the first waveguide; and a cladding layer surrounding the first and second waveguides. The first waveguide is configured such that the optical signal undergoes multimode interference to focus the fundamental mode at the end portion of the second waveguide.