Optical Waveguide Slit Segmentation for Leaked Light Control
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Solution Overview
Problem
Optical waveguide elements face interference issues due to high-order mode light beams leaking from branch portions, leading to deviations in branch ratios and deterioration of optical characteristics, especially when the substrate thickness is 20 μm or less.
Innovation Solution
An optical waveguide element is designed with a slab waveguide divided into regions by slits, where the refractive index of the slit is lower than the slab waveguide, and the shape of the boundary between these regions is configured to guide high-order mode light beams into the first slab waveguide region or outside the optical waveguide, preventing interference with downstream waveguides. Additionally, an absorbent material can be used in the first slab waveguide region to absorb the high-order mode light beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a slab waveguide is formed around the optical waveguide to absorb high-order mode light beam, then the optical characteristics are improved, but the high-order mode light beam still propagates in the slab waveguide and transfers to downstream optical waveguides causing interference
Solution Approach 1:
The slab waveguide is divided into multiple regions by introducing slits, creating a segmented structure. The first slab waveguide region is positioned to receive high-order mode light from the branch portion, while the second slab waveguide region is positioned away from downstream waveguides. This segmentation prevents the light from propagating to downstream optical waveguides while maintaining the absorption function.
Solution Approach 2:
The solution changes the spatial arrangement by positioning the first slab waveguide region along the optical waveguide formed on the downstream side of the second branch portion, and using slits to create vertical separation between regions. This dimensional reorganization confines the high-order mode light to specific regions, preventing interference with downstream waveguides.
2Volume of moving object
If the substrate thickness is reduced to 20 μm or less, then the device size is reduced, but the high-order mode light beam interference becomes particularly remarkable
Solution Approach 1:
By dividing the slab waveguide into first and second regions with slits, the patent confines high-order mode light to the first region, preventing it from reaching downstream waveguides. This segmentation is particularly effective in thin substrates (20 μm or less) where light confinement is more challenging, thus maintaining compact size while reducing interference.
Solution Approach 2:
The first slab waveguide region acts as an intermediary that captures and confines high-order mode light from the branch portion, preventing direct propagation to downstream waveguides. The slit structure serves as a barrier that mediates between the light source and downstream waveguides, blocking harmful light paths in thin substrate configurations.
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
This configuration effectively controls the propagation path of leaked high-order mode light beams, reducing interference with downstream waveguides and minimizing optical characteristic deterioration.
Implementation Method 1
a slab waveguide is formed between the two branched waveguides
Implementation Method 2
a slit that divides the slab waveguide into a first slab waveguide region near the first branch portion and a second slab waveguide region near the second branch portion is formed between the first branch portion and the second branch portion
Implementation Method 3
an absorbent material that absorbs a high-order mode light beam propagating in the slab waveguide is disposed in at least a part of the first slab waveguide region
Data Source
AI summary
Provided is an optical waveguide element that prevents leaked light generated at a forking section from entering a downstream optical waveguide such as another forking section, thereby affording minimal degradation of optical characteristics. The optical waveguide is characterized in that: at least one of two fork waveguides (20a, 20b) forking from a first forking section (20) comprises a second forking section (21, 22); slab waveguides (3c-1 to 3c-3) are formed between the two fork waveguides; and between the first forking section and the second forking section, slits (41, 42) are formed that partition the slab waveguides into a first slab waveguide area (3c-1) close to the first forking section and second slab waveguide areas (3c-2, 3c-3) close to the second forking section(s).