Segmented Optical Couplers for Ridge-to-Rib Waveguide Transitions
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Solution Overview
Problem
Conventional optical couplers in photonics chips face inefficiencies due to poor modal overlap, leading to coupling issues with non-guided or unwanted guided radiation modes, often requiring lengthy continuous tapers for signal transfer between waveguide cores.
Innovation Solution
A structure comprising a waveguide core and segmented layers with specific thickness and spacing arrangements, including a slab layer with varying thickness, to facilitate efficient transition between ridge and rib waveguide cores, reducing the need for lengthy tapers and improving coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional continuous tapers are used for waveguide core transitions, then coupling efficiency may be maintained, but the device length increases significantly
Solution Approach 1:
The continuous taper structure is divided into multiple discrete segments with varying thicknesses along the longitudinal axis. These segments create a stepped transition profile that approximates the continuous taper function while significantly reducing the overall device length. The segmented approach allows for optimized coupling efficiency without requiring the full length of a conventional continuous taper.
2Manufacturing precision
If the slab layer thickness is reduced below the waveguide core thickness, then fabrication tolerance is improved, but modal overlap may deteriorate
Solution Approach 1:
The slab layer thickness is varied locally across different segments rather than maintaining a uniform thickness. Each segment has a specific thickness optimized for its position in the transition, allowing the structure to maintain good modal overlap while accommodating fabrication tolerances. The local variation in thickness enables the system to achieve both manufacturing precision and optical performance.
Data Source
AI summary
Structures for an optical coupler and methods of fabricating a structure for an optical coupler. A first plurality of segments are positioned with a first spaced arrangement along a longitudinal axis, and a second plurality of segments are positioned with a second spaced arrangement along the longitudinal axis between the first plurality of segments and a waveguide core. A slab layer has a plurality of sections respectively connected to the second plurality of segments. The second plurality of segments have a first thickness, and the slab layer has a second thickness that is less than the first thickness.