Tapered Photonic Waveguide Coupling to Optical Fiber
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Solution Overview
Problem
Coupling optical signals from 0.2 μm×1.0 μm single mode silicon photonic waveguides to 8-10 μm core size single mode optical fibers is challenging while maintaining high optical coupling efficiency.
Innovation Solution
A tapered photonic waveguide structure within a photonic substrate is used, where the waveguide tapers in width along its longitudinal length, and a portion of the optical fiber core is partially exposed by removing the cladding, allowing for efficient coupling of optical signals to the fiber core, optionally with additional satellite tapered waveguides for mode broadening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a 0.2 μm×1.0 μm single mode waveguide is used to couple optical signals to an 8-10 μm core size single mode optical fiber, then the waveguide dimensions are compatible with integrated photonic devices, but the optical coupling efficiency is difficult to maintain at high levels
Solution Approach 1:
The waveguide width is varied along its length, transitioning from 0.2 μm at the input to a wider dimension at the output end. This gradual parameter change allows the optical mode to expand and match the larger fiber core size, achieving high coupling efficiency without complex alignment mechanisms
Solution Approach 2:
The coupling transition is achieved by modifying the waveguide in the lateral dimension (width) while maintaining propagation in the longitudinal dimension. This dimensional transformation enables mode size matching between the small waveguide and large fiber core
2Reliability
If the waveguide width is gradually increased to match the fiber core size, then the mode field diameter is better matched for coupling, but the coupling length increases
Solution Approach 1:
The waveguide width is made dynamic along the propagation direction, creating a gradual transition rather than an abrupt change. This dynamic geometry allows the optical mode to adapt progressively to the changing waveguide dimensions, achieving effective mode matching in a compact length
Solution Approach 2:
The linear taper provides a smooth, continuous transition in waveguide width along its length. This curved/gradual geometric transition prevents abrupt mode disturbances and enables efficient adiabatic coupling over a reduced interaction length
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
Achieves high coupling efficiency, with over 92% of the optical signal power being transferred from the photonic waveguide to the optical fiber, enhancing the transmission of optical signals.
Implementation Method 1
A tapered photonic waveguide structure within a photonic substrate may include a tapered region that progressively tapers in width along a longitudinal length of the tapered photonic waveguide structure
Data Source
AI summary
A photonic waveguide structure may include a tapered photonic waveguide structure within a photonic substrate, such that the tapered photonic waveguide structure has a tapered region that progressively tapers in width along a longitudinal length of the tapered photonic waveguide structure. The photonic waveguide structure also includes an optical fiber waveguide having a core region and a cladding region, whereby a portion of the core region is partially exposed by removing a portion of the cladding region. An outer surface of the portion of the core region that is partially exposed is substantially coupled to the tapered photonic waveguide structure. An optical signal propagating along the tapered photonic waveguide structure is coupled from the tapered region of the tapered photonic waveguide structure to the core region of the optical fiber waveguide via the core region that is partially exposed.