Twin-Arm Waveguide for Low-Loss Slot Waveguide Coupling
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Solution Overview
Problem
Conventional connecting structures for optical waveguides cannot be directly applied to slot waveguides due to their unique electric field and electromagnetic wave energy distribution, which differs from conventional waveguides.
Innovation Solution
A waveguide connecting structure that includes a light branching element and a twin-arm waveguide with cores in a cladding, where the arm waveguides gradually narrow to match the core spacing of the slot waveguide, allowing for low-loss and smooth electromagnetic field mode conversion from a high-index to a low-index region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional connecting structures are used to connect waveguides, then connection is achieved, but the structure cannot be applied to slot waveguides due to different electric field and electromagnetic wave energy distribution
Solution Approach 1:
The patent introduces an intermediate coupling structure consisting of two waveguides arranged in parallel between the input waveguide and the slot waveguide. This intermediate structure serves as a mediator to bridge the gap between conventional waveguide modes and slot waveguide modes, enabling efficient mode conversion without directly applying conventional connecting structures to the slot waveguide.
Solution Approach 2:
The patent changes the geometric parameters of the waveguide structure by gradually varying the spacing between the two parallel waveguides in the intermediate coupling section. This gradual parameter change enables smooth mode transformation from conventional waveguide modes to slot waveguide modes, resolving the incompatibility between different waveguide types.
2Ease of manufacture
If the spacing between arm waveguides is maintained constant, then manufacturing is simplified, but mode conversion to slot waveguide is inefficient
Solution Approach 1:
The patent applies local quality variation by making the spacing between the two arm waveguides different at different locations along the waveguide length. The spacing is larger at the input end and gradually decreases toward the output end, creating optimal local conditions for mode conversion at each position while maintaining overall manufacturing feasibility.
Solution Approach 2:
The patent introduces a dynamic geometric configuration where the spacing between arm waveguides varies continuously along the waveguide length rather than remaining static. This dynamic spacing adjustment optimizes the coupling between waveguide modes throughout the interaction region, minimizing energy loss during mode conversion.
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
Enables efficient and low-loss conversion of electromagnetic field modes from conventional waveguides to slot waveguides, facilitating smooth connection and reducing propagation loss.
Implementation Method 1
a twin-arm waveguide including a pair of arm waveguides which output the light components branched by the light branching element to a slot waveguide including two cores arranged in parallel at a narrow spacing, wherein the pair of arm waveguides have cores formed in a cladding on a substrate and having a refractive index higher than that of the cladding, and are formed such that a spacing between the pair of arm waveguides gradually narrows and becomes equal to a core spacing of the slot waveguide
Data Source
AI summary
A waveguide connecting structure includes a light branching element (111) for branching light from an input optical waveguide (201) including one core into two branched light components having the same optical power and the same phase, and a twin-arm waveguide (113) including a pair of arm waveguides (113A, 113B) for outputting the light components branched by the light branching element to a slot waveguide (202) including two cores arranged in parallel at a narrow spacing. The pair of arm waveguides have cores formed in a cladding on a substrate and having a refractive index higher than that of the cladding, and are formed such that the spacing between them gradually narrows and becomes equal to the core spacing of the slot waveguide from the core input ends into which the branched light components enter toward the core output ends from which the light components are output to the slot waveguide.