Polarization Splitter-Rotator PIN Junction Free-Carrier Sweep
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Solution Overview
Problem
High optical power photonic telecommunication systems face significant optical losses due to free-carrier absorption (FCA) induced by two-photon absorption (TPA) in silicon waveguides, which limits the functionality and reliability of photonic chips, especially in components like the Polarization Splitter-Rotator (PSR) that handle large optical powers.
Innovation Solution
Incorporating reverse biased PIN junctions in the waveguide layers of the PSR, which generates an electric field that sweeps away photo-generated free carriers, thereby reducing the population of free carriers and mitigating the negative impact of FCA. This solution can be implemented in silicon or other materials like indium phosphide, polysilicon, or nitrides, and can be applied to multiple layers or specific sections of the PSR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high optical power is transmitted through silicon waveguides in the PSR, then the optical signal strength is improved, but free-carrier absorption losses increase due to two-photon absorption
Solution Approach 1:
The patent applies reverse bias to the PIN junction to create an electric field that converts the harmful effect of free-carrier absorption into a beneficial outcome by sweeping photo-generated carriers out of the waveguide. The reverse bias voltage generates an electric field that drifts carriers away from the optical mode, transforming the harmful FCA effect into a controllable parameter that can be optimized for minimal loss.
Solution Approach 2:
The patent changes the electrical parameter (applying reverse bias voltage) to the PIN junction to control the free-carrier population in the waveguide. By adjusting the reverse bias voltage, the electric field strength is modified, which directly controls the carrier sweep-out efficiency and thus the FCA losses, enabling optimization of the trade-off between optical power transmission and loss.
2Loss of energy
If reverse bias is applied to the PIN junction to reduce free-carrier absorption, then optical losses are reduced, but additional electrical control complexity is introduced
Solution Approach 1:
The PIN junction serves multiple functions: it acts as the core polarization-splitting element and simultaneously provides free-carrier management through reverse bias. This multi-functionality eliminates the need for separate carrier management structures, reducing overall device complexity while achieving loss reduction.
Solution Approach 2:
The reverse-biased PIN junction self-regulates the free-carrier population through the electric field it generates. The structure inherently manages its own carrier density by sweeping out photo-generated carriers, eliminating the need for external carrier management mechanisms and simplifying the overall device architecture.
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 reverse biased PIN junctions effectively reduce non-linear power losses, ensuring a more efficient transmission of high power optical signals by maintaining a linear relationship between input and output powers, thereby enhancing the reliability and efficiency of photonic chips.
Implementation Method 1
Incorporating reverse biased PIN junctions in the waveguide layers of the PSR, which generates an electric field that sweeps away photo-generated free carriers
Implementation Method 2
free-carrier absorption (FCA) induced by two-photon absorption (TPA) in silicon waveguides
Implementation Method 3
free-carrier absorption (FCA) induced by two-photon absorption (TPA) in silicon waveguides
Implementation Method 4
a first biased layer optically coupled to the input waveguide where the first biased layer converts the TM light into TE light
Data Source
AI summary
Embodiments herein describe reverse biasing one or more PIN junctions formed in at least one layer of a PSR. The resulting electric fields in the PIN junctions overlap with the optical path of the optical signal and sweep away photo-generated hole-electron free carriers away. That is, the electric fields in the PIN junctions remove the free carriers from the path of the optical signal and reduces the population of the free carriers, thereby mitigating the negative impact of free-carrier absorption (FCA).