SOI Waveguide with Suspended Oxide Layer for Low Loss
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Solution Overview
Problem
Current silicon-photonics technology on SOI wafers with buried oxide layers faces high losses, particularly in TM modes, limits thermal dissipation, and restricts design flexibility for optoelectronic devices, making them unsuitable for applications requiring both TE and TM modes and integration of multiple components.
Innovation Solution
An integrated optical device with a buried structure that includes a cavity filled with dielectric material, laterally offset from active components, forming a waveguide with improved confinement and reduced losses, allowing for independent biasing and increased thermal dissipation, and enabling the integration of diverse optical guides within the same die.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a thin buried oxide layer (2-3 μm) is used in SOI wafers, then the device size is reduced and integration is enabled, but propagation losses increase significantly especially for TM modes
Solution Approach 1:
The patent divides the oxide layer into two distinct segments: a thin buried oxide layer (2-3 μm) for mechanical support and a thicker suspended oxide layer (5-10 μm) for optical confinement. This segmentation allows each layer to fulfill its specific function optimally - the thin buried layer maintains device integration while the thick suspended layer reduces propagation losses by providing adequate optical confinement for both TE and TM modes.
Solution Approach 2:
The patent introduces a vertical dimension solution by creating a suspended oxide layer above the buried oxide, forming a three-layer oxide structure. This dimensional approach allows the optical waveguide to access the thicker oxide region for better confinement while the device remains integrated on the substrate through the thin buried oxide layer.
2Loss of energy
If the oxide layer thickness is increased to reduce propagation losses, then TM mode confinement is improved, but thermal dissipation capability is reduced
Solution Approach 1:
The oxide layer is segmented vertically into a thin buried oxide layer in contact with the substrate for thermal dissipation, and a thicker suspended oxide layer for optical confinement. This segmentation resolves the contradiction by assigning thermal management function to the substrate-contacting thin layer and optical confinement function to the suspended thick layer.
Solution Approach 2:
Different regions of the oxide structure are given different thicknesses to fulfill different functions: the buried oxide layer near the substrate is kept thin (2-3 μm) to maintain thermal pathways, while the suspended oxide layer is made thick (5-10 μm) locally where optical confinement is needed, creating local quality variations that satisfy both thermal and optical requirements.
3Stability of the object's composition
If the waveguide section is increased to achieve biasing independence, then mode symmetry is improved, but device dimensions increase
Solution Approach 1:
The patent changes the oxide layer thickness parameter (creating a thick suspended oxide layer of 5-10 μm) to achieve better optical confinement and reduced propagation losses. This parameter change allows the waveguide to maintain stable operation with reduced losses without requiring increased waveguide dimensions for symmetry, as the improved confinement naturally enhances mode stability.
4Adaptability or versatility
If optical coupling structures are added to expand beam cross section, then optical coupling with external devices is enabled, but coupling losses increase (3-7 dB)
Solution Approach 1:
The patent changes the oxide layer thickness parameter to create a thick suspended oxide layer that provides superior optical confinement. This parameter change improves the overall optical performance and reduces propagation losses throughout the waveguide, which helps compensate for the coupling losses introduced by external coupling structures, thereby improving net coupling efficiency.
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 solution reduces propagation losses, enhances thermal management, and increases design flexibility by allowing for the integration of various optical components and guides with different characteristics, improving the performance of optoelectronic devices beyond traditional SOI limitations.
Implementation Method 1
the suspended oxide layer (5-10 μm) arranged on the epitaxial region... forming an optical guide... improved confinement and reduced losses
Data Source
AI summary
An integrated optical device, including: a semiconductor body delimited by a top surface; and at least one buried cavity, which extends in the semiconductor body, at a distance from the top surface, so as to delimit at the bottom a front semiconductor region, which functions as an optical guide.