Rib Waveguide Polarization Rotator for PIC Integration
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Solution Overview
Problem
Existing polarization rotators are not suitable for micron-scale waveguide platforms, which are necessary for reliable operation of polarization-sensitive modulators in photonic-integrated-circuits due to random polarization of light from optical fibers, leading to inconsistent performance.
Innovation Solution
A polarization rotator design featuring a rib waveguide with a slab and ridge portion, capable of rotating light polarization on a micron-scale silicon platform, including a polarization-dependent splitter to separate and rotate TE and TM polarized light, ensuring reliable operation across a broad wavelength range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional polarization rotator is used on a 220 nm silicon-on-insulator platform, then polarization rotation is achievable through adiabatic mode conversion, but the device length becomes on the order of centimetres which is unsuitable for photonic-integrated-circuits
Solution Approach 1:
The patent changes the waveguide geometric parameters to achieve polarization rotation on a micron-scale platform. Specifically, it uses a rib waveguide with optimized dimensions (slab thickness of 220 nm, ridge height of 3 μm, ridge width of 5 μm) that enables strong mode hybridization and adiabatic mode conversion within a compact length of 400-950 μm, making it suitable for photonic-integrated-circuits while maintaining reliable polarization rotation functionality
Solution Approach 2:
The patent introduces a three-dimensional rib waveguide structure with specific vertical and horizontal dimensions that enables polarization rotation in a compact footprint. The rib waveguide's vertical confinement (3 μm ridge height above 220 nm slab) and horizontal confinement (5 μm ridge width) create strong mode hybridization that achieves polarization conversion in a much shorter length than conventional planar waveguides
2Volume of moving object
If a small waveguide or waveguide with two-dimensional structure is used, then the device size is reduced for integration, but the difference in propagation profiles between TE and TM light causes large polarization-dependent effects that limit operating wavelength ranges
Solution Approach 1:
The patent optimizes the waveguide geometric parameters including slab thickness (220 nm), ridge height (3 μm), and ridge width (5 μm) to achieve polarization rotation functionality while maintaining a compact size suitable for integration. These parameter changes enable the device to operate across broad wavelength ranges including O-, C-, and L-bands despite the small waveguide dimensions
Solution Approach 2:
The patent creates different geometric configurations in different regions of the waveguide structure. The rib waveguide has a specific cross-sectional geometry with 220 nm slab and 3 μm ridge height that provides local optical properties optimized for polarization rotation, while the overall device maintains compact dimensions for integration
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 provides efficient polarization rotation with high conversion efficiency and robustness against fabrication variations, maintaining performance across the O-, C-, and L-bands, and is suitable for implementation in photonic-integrated-circuits.
Implementation Method 1
the mode hybridization effect utilized in these devices during adiabatic mode conversion is relatively strong
Implementation Method 2
the mode hybridization effect utilized in these devices during adiabatic mode conversion is relatively strong
Data Source
AI summary
A polarization rotator and a polarization stabilizer. The polarization rotator includes a rib waveguide. The rib waveguide including: a slab portion; and a ridge portion, which is disposed along a surface of the slab portion. The slab portion has a first slab region whose width, as measured in a direction perpendicular to a guiding direction of the waveguide, increases from a first slab width to a second slab width along a first length, and the ridge portion has a first ridge region whose width, as measured in the same direction as the slab widths, decreases from a first ridge width to a second ridge width along the same first length; such that the rotator is configured to rotate the polarization of light during its transmission through the rib waveguide.