Diamond Spot Size Converter for Low-Loss Fiber Edge Coupling
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Solution Overview
Problem
Existing optical fiber-to-chip couplings face challenges in efficiently transitioning light signals due to mismatched spot sizes and stringent alignment requirements, leading to high loss and reliability issues, particularly in silicon-based photonic integrated circuits (PICs).
Innovation Solution
The implementation of a diamond-shaped optical coupler with a waveguide and intermediary elements, featuring an inversely tapered design and varying pitch, allows for efficient conversion of light between optical fibers and PICs, accommodating higher misalignment tolerances and reducing manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional optical fiber-to-chip couplings are used, then light coupling is achieved, but high coupling loss occurs due to mismatched spot sizes
Solution Approach 1:
The patent introduces an intermediary spot size converter structure between the optical fiber and the silicon waveguide. This converter acts as a mediator that gradually transforms the spot size from the fiber mode to the waveguide mode, avoiding direct coupling between mismatched modes and thereby reducing coupling loss.
Solution Approach 2:
The spot size converter employs continuous parameter changes in its geometric dimensions along the propagation direction. The width and height of the converter structure vary gradually, enabling adiabatic mode transformation that minimizes reflection and coupling loss while accommodating the spot size mismatch.
2Reliability
If conventional optical fiber-to-chip couplings are used, then light coupling is achieved, but stringent alignment requirements lead to reliability issues
Solution Approach 1:
The spot size converter serves as a tolerance-compensating intermediary structure. Its extended interaction length and gradual mode transformation capability provide inherent alignment tolerance, reducing the impact of manufacturing variations and assembly misalignments on coupling reliability.
Solution Approach 2:
The coupling structure is segmented into distinct regions: the fiber interface region, the spot size converter region with varying dimensions, and the waveguide interface region. This segmentation allows each region to be optimized independently, with the converter region specifically designed to provide alignment tolerance.
3Ease of operation
If diamond-shaped optical coupler with varying pitch is implemented, then misalignment tolerance is improved, but device complexity increases
Solution Approach 1:
The spot size converter employs an asymmetric diamond-shaped cross-section with varying pitch between structural elements. This asymmetric geometry is specifically designed to match the mode field distribution transformation requirements, providing enhanced alignment tolerance while maintaining manufacturability through standard fabrication processes.
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 configuration achieves low coupling loss and polarization mode dispersion, with improved reliability and manufacturability, enabling efficient light transfer with reduced sensitivity to alignment errors.
Implementation Method 1
The intermediary area preferably arranged over, in a vertical direction, the lower area and including two or more intermediary elements with an upper area arranged over the intermediary area. The upper area including one or more upper elements, where the two or more intermediary elements comprise a varying pitch along the propagation direction
Implementation Method 2
The lower area preferably includes a waveguide with a first end, a second end, and an inversely tapered portion
Data Source
AI summary
An optical coupler configured to couple light along a propagation direction is disclosed. The optical coupler includes a lower area. The lower area includes a waveguide including a first end, a second end, and an inversely tapered portion. The optical coupler includes an intermediary area arranged over, in a vertical direction, the lower area. The intermediary area includes two or more intermediary elements. The optical coupler includes an upper area arranged over the intermediary area. The upper area includes one or more upper elements.