Tapered Planar Waveguide Polarization Rotating Splitter
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Solution Overview
Problem
Conventional polarization beam splitters and combiners are not suitable for integration into photonic integrated circuits due to their bulkiness, making it difficult to implement polarization rotation for high refractive-index-contrast waveguides, which are common in silicon/silicon oxide PICs, leading to challenges in handling polarization-diverse signals.
Innovation Solution
A photonic integrated circuit (PIC) with two tapered planar waveguide cores separated by a narrow gap, where a laterally tapered slab core facilitates adiabatic mode conversion for polarization rotation between TE and TM modes, enabling efficient signal conversion and operation as both a splitter and combiner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional polarization beam splitters are used, then polarization separation functionality is achieved, but the device becomes bulky and unsuitable for integration into photonic integrated circuits
Solution Approach 1:
The patent replaces the conventional mechanical prism-based polarization beam splitter with a planar waveguide structure that uses evanescent field coupling and adiabatic mode conversion. This substitution enables polarization separation functionality to be integrated into a compact planar format suitable for photonic integrated circuits, reducing device volume from bulk 3D prisms to 2D planar waveguides.
Solution Approach 2:
The invention transitions from three-dimensional bulk optical prisms to two-dimensional planar waveguide cores. By confining light propagation to a planar geometry with sub-wavelength thickness, the device achieves polarization separation in a reduced dimensional footprint, enabling integration into photonic circuits while maintaining the essential polarization manipulation functionality.
2Productivity
If adiabatic mode conversion is used for polarization rotation, then signal conversion efficiency exceeds 90%, but the waveguide structure becomes more complex
Solution Approach 1:
The patent achieves high signal conversion efficiency by carefully controlling geometric parameters of the waveguide structure, including the thickness gradient of the slab core (varying from 220 nm to 90 nm), the gap width between waveguide cores (300 nm), and the length of the adiabatic transition region (500 nm). These parameter optimizations enable adiabatic mode conversion with efficiency exceeding 90% across the 1.4-1.7 μm wavelength range.
3Adaptability or versatility
If a tapered slab core is used to bridge the gap between waveguide cores, then polarization rotation is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The patent segments the waveguide structure into distinct functional regions: input waveguide core, tapered slab core with gradient thickness, and output waveguide core. This segmentation allows each component to be optimized independently for its specific function while using standard CMOS-compatible fabrication processes, making the complex tapered structure manufacturable with conventional precision capabilities.
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 achieves signal-conversion efficiency greater than 90% across a wavelength range of 1.4 μm to 1.7 μm, allowing for the integration of polarization-rotating functionality within a compact PIC, compatible with standard CMOS fabrication processes.
Implementation Method 1
the light crossing between the two waveguide cores by way of adiabatic mode conversion undergoes a polarization rotation between the TM and TE polarizations
Data Source
AI summary
A photonic integrated circuit (PIC) having two tapered planar waveguide cores that are separated from one another by a relatively narrow gap, with each of these waveguide cores having a respective portion thereof located on a tapered planar slab core. The relative positions of the slab core and the two waveguide cores are such that the light crossing between the two waveguide cores undergoes a polarization rotation between the TM and TE polarizations with a relatively low insertion loss. The corresponding waveguide structure can be used as a relative polarization-rotating splitter for light propagating in one direction or as a relative polarization-rotating combiner for light propagating in the opposite direction. At least some embodiments of the disclosed PIC can advantageously be fabricated using a complementary metal oxide semiconductor technology and/or a conventional silicon-on-insulator platform.