Polarization Splitter Rotator Using Suspended Polymer Waveguides
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Solution Overview
Problem
Existing polarization splitter rotators (PSRs) in silicon photonics are lossy, limiting the performance of optical receivers due to intrinsic scattering, absorption, and backscattering in silicon and poly-silicon materials.
Innovation Solution
A polarization splitter rotator design featuring a pair of waveguides on a lower layer and a bus waveguide on an upper layer, with symmetric and asymmetric widening configurations, to efficiently hybridize TM0 and TE1 mode light with low loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a PSR is implemented using crystalline silicon, poly-silicon, and silicon nitride, then the device can be manufactured with existing processes, but the insertion loss increases due to intrinsic scattering and absorption in silicon materials
Solution Approach 1:
The patent extracts the light-guiding function from silicon waveguides (which cause scattering and absorption losses) and transfers it to suspended polymer waveguides. The polymer material is suspended above the silicon substrate, physically separating the optical path from the lossy silicon material while maintaining manufacturability through standard PCB-like fabrication processes.
Solution Approach 2:
The patent employs a composite structure combining silicon substrate with polymer waveguide materials (such as SU-8 or cyclic olefin copolymer). This composite approach leverages the manufacturing advantages of silicon while utilizing the low-loss optical properties of polymer materials for light transmission.
2Ease of manufacture
If poly-silicon is used in the PSR, then the device can be fabricated using standard semiconductor processes, but the return loss decreases due to large back scattering from poly-silicon
Solution Approach 1:
The patent removes poly-silicon from the optical path entirely, using it only as a structural support layer beneath the suspended polymer waveguides. This extraction eliminates the backscattering problem while retaining the manufacturability benefits of poly-silicon fabrication processes.
Solution Approach 2:
The patent introduces an intermediate polymer waveguide layer that mediates between the poly-silicon substrate and the optical signal. The polymer acts as an optical intermediary that does not scatter light back, allowing the poly-silicon to remain in the structure for mechanical support without degrading optical performance.
3Adaptability or versatility
If silicon waveguides are used to guide light, then the device can be integrated with existing silicon photonics platforms, but the insertion loss increases due to 2-photon absorption at high optical powers
Solution Approach 1:
The patent extracts the light-guiding function from silicon waveguides and assigns it to polymer waveguides instead. This allows the device to be integrated with silicon photonics platforms (through the silicon substrate and coupling interfaces) while eliminating 2-photon absorption losses in the primary light transmission path.
Solution Approach 2:
The patent applies different material qualities to different regions: silicon is used where mechanical strength and platform integration are needed (substrate, coupling regions), while low-loss polymer material is used specifically in the suspended waveguide regions where high-power optical transmission occurs, optimizing each region for its primary function.
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 proposed PSR achieves exceptional performance with low insertion loss and high extinction ratio in both the O-band and C-band, outperforming traditional designs by minimizing material-related losses.
Implementation Method 1
a bus waveguide disposed on a second layer, above the first layer, at least partially overlapping portions of the first lower waveguide and the second lower waveguide
Data Source
AI summary
A polarization splitter rotator includes a first lower waveguide and a second lower waveguide disposed on a first layer, the first lower waveguide and the second lower waveguide, in a first portion of the device, widening symmetrically as the first lower waveguide and the second lower waveguide extend from an input end of the device to an output end of the device, and, in a second portion of the device, at least the second lower waveguide widening further, asymmetrically, from the first lower waveguide, and a bus waveguide disposed on a second layer, above the first layer, at least partially overlapping portions of the first lower waveguide and the second lower waveguide.