Tilted Waveguide Polarisation Converter for Photonic Integrated Circuits
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Solution Overview
Problem
Existing methods for manufacturing light polarisation converters in photonic integrated circuits (PICs) face challenges with wet etching techniques, which result in irregular surfaces and lack of control over manufacturing tolerances, affecting light propagation and polarisation conversion efficiency.
Innovation Solution
A semiconductor light polarisation converter is designed with a waveguide structure where the second waveguide portion is offset from the first waveguide portion, and an intermediate waveguide portion is at an angle, allowing for polarisation conversion without the need for wet etching, thereby improving control over light propagation and manufacturing tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet etching techniques are used to manufacture light polarisation converters, then manufacturing process is simple, but surface irregularities occur and manufacturing precision deteriorates
Solution Approach 1:
The patent replaces the chemical wet etching process with a mechanical/physical deposition process. Specifically, it uses selective epitaxial growth to form the tilted waveguide structure, where silicon dioxide is deposited in specific regions to create the desired geometry without chemical etching. This substitution eliminates surface irregularities while maintaining manufacturing feasibility through controlled deposition processes.
Solution Approach 2:
The patent changes the manufacturing approach from removing material (etching) to adding material (deposition). By using selective epitaxial growth with controlled deposition parameters, the tilted waveguide structure is formed with precise surface regularity. The deposition depth, temperature, and rate are controlled to achieve the required geometric precision without the surface defects associated with wet etching.
2Ease of manufacture
If wet etching techniques are used to manufacture light polarisation converters, then manufacturing process is straightforward, but control over manufacturing tolerances is poor
Solution Approach 1:
The patent replaces the chemical wet etching process with a mechanical/physical deposition process. Specifically, it uses selective epitaxial growth to form the tilted waveguide structure, where silicon dioxide is deposited in specific regions to create the desired geometry without chemical etching. This substitution eliminates surface irregularities while maintaining manufacturing feasibility through controlled deposition processes.
Solution Approach 2:
The patent implements feedback control in the selective epitaxial growth process. By monitoring and controlling deposition parameters such as temperature, pressure, and precursor flow rates, the manufacturing process achieves precise control over the tilted waveguide geometry. The feedback mechanism ensures that manufacturing tolerances are maintained within specified limits, improving upon the poor tolerance control of wet etching methods.
3Device complexity
If conventional waveguide structures are used, then device complexity is low, but polarisation conversion efficiency is insufficient
Solution Approach 1:
The patent introduces asymmetry into the waveguide structure by creating a tilted configuration through selective epitaxial growth. The silicon dioxide layers are deposited at specific angles and positions to form an asymmetric waveguide geometry that enables effective polarisation conversion. This asymmetric structure allows the waveguide to couple between different polarisation modes (TE and TM) while maintaining relative structural simplicity, thus improving conversion efficiency without excessive complexity.
Solution Approach 2:
The patent adds a dimensional aspect to the waveguide structure by creating tilts in the waveguide geometry through selective deposition. The tilted waveguide portions extend in three dimensions, introducing a angular component that enables polarisation conversion. This dimensional enhancement allows the structure to perform polarisation conversion functionality while maintaining a relatively simple planar layout, balancing device complexity with conversion 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
This approach enables precise control over light polarisation conversion, reduces surface irregularities, and enhances manufacturing tolerances, leading to improved performance and reliability of light polarisation converters in PICs.
Implementation Method 1
the waveguide comprises a first waveguide portion in contact with the first surface, and a second waveguide portion in contact with the second surface. The second surface is offset from the first surface along a first axis and a second axis each perpendicular to a light propagation direction
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A light polarisation converter for a photonic integrated circuit, comprising: a substrate and a waveguide. The substrate comprises a first surface and a second surface. The waveguide comprises a first waveguide portion in contact with the first surface, and a second waveguide portion in contact with the second surface. The second surface is offset from the first surface along a first axis and a second axis. Each axis is perpendicular to a light propagation direction for converting polarisation of the light. The second waveguide portion is offset from the first waveguide portion.