Optical Mode Splitter Using Tapered Internal Waveguides
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Solution Overview
Problem
Existing optical waveguide splitters face performance degradation due to finite gaps between output waveguides, which hinder effective separation of spatial modes in multimode waveguides.
Innovation Solution
A spatial mode splitter design featuring internal waveguides connected to input and output waveguides with a transition and decoupling region, where the gap between internal waveguides is carefully tapered to ensure at least 80% power transmission of fundamental and first-order spatial modes to respective output waveguides, utilizing adiabatic evolution principles to maintain mode integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an asymmetric Y-junction is used to split spatial modes, then mode separation is achieved, but performance degrades due to finite gap discontinuity
Solution Approach 1:
The patent introduces an intermediate tapered waveguide section between the input waveguide and the asymmetric output waveguides. This intermediate section acts as a mediator that gradually transitions the mode field distribution, avoiding the abrupt discontinuity caused by the finite gap at the Y-junction. The tapered geometry allows adiabatic evolution of the optical modes, maintaining high coupling efficiency and preventing performance degradation.
Solution Approach 2:
The patent employs parameter changes by varying the waveguide dimensions along the propagation direction. The tapered waveguide section features continuously changing width and gap parameters, transitioning from the input waveguide dimensions to the asymmetric output waveguide dimensions. This gradual parameter change enables adiabatic mode evolution, allowing the optical field to adapt smoothly to the changing geometry without exciting unwanted modes or causing reflections.
2Ease of manufacture
If fabrication limitations result in finite gap at Y-junction, then manufacturing is simplified, but performance degradation occurs
Solution Approach 1:
The patent converts the harmful effect of the finite gap discontinuity into a beneficial tapered transition. Instead of attempting to fabricate an ideal zero-gap Y-junction (which would be more difficult), the design embraces the finite gap and uses it as part of a controlled tapered geometry. This tapered section transforms the abrupt discontinuity into a gradual transition, turning what would be a performance-degrading feature into a functional element that enables adiabatic mode evolution.
3Reliability
If waveguide gap is reduced to improve mode coupling, then manufacturing precision requirements increase
Solution Approach 1:
The patent applies dynamics by making the waveguide geometry variable rather than static. The tapered waveguide section features continuously varying dimensions along the propagation direction, with the gap and width changing gradually from the input to the output. This dynamic geometry allows the system to maintain good mode coupling throughout the transition, with the gap being larger at the input (easier to manufacture) and gradually reducing toward the output, rather than requiring a uniformly small gap throughout.
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
The splitter effectively transmits at least 80% of the input power in the fundamental and first-order spatial modes to their respective output waveguides, overcoming the limitations of finite gaps and enhancing performance.
Implementation Method 1
utilizing adiabatic evolution principles to maintain mode integrity
Data Source
AI summary
A splitter. In some embodiments, the splitter includes an input waveguide; a first output waveguide; a second output waveguide; a first internal waveguide, connected to the input waveguide and to the first output waveguide, and a second internal waveguide, coupled to the first internal waveguide and connected to the second output waveguide. The splitter may be configured, when fed, at the input waveguide, power in a fundamental mode of the input waveguide or power in a first order spatial mode of the input waveguide: to transmit at least 80% of the power in the fundamental mode to the first output waveguide, and to transmit at least 80% of the power in the first order spatial mode to the second output waveguide.