Tapered Rib Waveguide for Low-Loss Optical Mode Expansion
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Solution Overview
Problem
Conventional optical waveguides with channel structures experience side wall roughening during formation, leading to increased optical loss and reflection due to light scattering, and struggle with optical confinement and mode field expansion.
Innovation Solution
The proposed optical device incorporates a rib waveguide with a tapered structure, featuring a rib portion and slab portions, which reduces side wall roughening and allows for weak optical confinement, enabling efficient spot-size conversion with reduced optical coupling loss and reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a channel waveguide structure is used, then the waveguide can be formed with a simple structure, but side wall roughening occurs during etching leading to increased optical loss and reflection
Solution Approach 1:
The patent applies local quality by transitioning from a uniform channel waveguide structure to a rib waveguide structure with varying rib widths. The rib waveguide has a tapered structure where the rib width changes along the propagation direction, creating different local optical confinement properties. This allows the waveguide to have regions with strong confinement (narrower rib sections) and regions with weak confinement (wider rib sections), optimizing performance while reducing the harmful effects of side wall roughening on optical loss.
2Device complexity
If a channel waveguide structure is used, then the waveguide can be formed with a simple structure, but optical reflection increases due to light scattering from side wall roughening
Solution Approach 1:
The rib waveguide structure creates local variations in optical confinement through its tapered design. By having different rib widths at different positions, the structure provides regions with different scattering characteristics, reducing overall optical reflection while maintaining structural simplicity.
3Reliability
If the waveguide core is thickened, then optical confinement is improved, but the influence of side wall roughening becomes more notable
Solution Approach 1:
The patent applies parameter changes by varying the rib width parameter along the waveguide propagation direction. The tapered rib waveguide structure allows the effective core thickness to be dynamically adjusted through the rib width variation, providing strong optical confinement in certain regions while minimizing the impact of side wall roughening in other regions, thus resolving the contradiction between confinement and loss.
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 rib waveguide structure effectively prevents optical scattering-induced losses and reflections, enhances mode field expansion, and improves coupling efficiency by reducing core width, particularly for TE light, with minimal polarization dependence.
Implementation Method 1
a rib waveguide that is connected at a side at which the waveguide width of the channel waveguide is increased and that includes a rib portion and slab portions. The rib waveguide includes a tapered waveguide in which a rib width of the rib portion increases in a tapered manner
Data Source
AI summary
An optical device includes a channel waveguide that has a waveguide width that increases in a tapered manner, and a rib waveguide that is connected to a side at which the waveguide width of the channel waveguide is increased and that includes a rib portion and slab portions. The rib waveguide includes a tapered waveguide in which a rib width of the rib portion increases in a tapered manner with distance from a part at a side at which the channel waveguide is connected.