Ribbed Waveguide Structure with Variable-Height Slabs for Fast Phase Shifters
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Solution Overview
Problem
In photonic integrated circuits, there is a trade-off between achieving significant light confinement with low transmission loss and minimizing the bending radius of silicon waveguides, while maintaining high phase shifter speed due to increasing resistance with reduced slab thickness.
Innovation Solution
A waveguide structure with varying thickness profiles for slab and contact portions, including p-n or p-i-n junctions, is designed to balance light confinement, reduce transmission loss, and enhance phase shifter speed by using CMOS-compatible manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the slab thickness is reduced to achieve smaller bending radii, then the bending radius is minimized, but the resistance increases which reduces phase shifter speed
Solution Approach 1:
The waveguide structure employs different doping concentrations in different regions: heavily doped contact portions (10^19 to 10^21 atoms/cm³) at the contacts, medium doped slab portions (10^17 to 10^19 atoms/cm³) in the slab regions, and lightly doped waveguide portions (10^16 to 10^18 atoms/cm³) in the waveguide regions. This local variation in doping quality allows the structure to maintain low resistance at contacts while preserving phase shifter speed in the waveguide regions, resolving the contradiction between small bending radius and high phase shifter speed.
2Volume of moving object
If the slab thickness is reduced to minimize bending radius, then the bending radius is reduced, but transmission loss increases
Solution Approach 1:
The structure uses locally optimized doping concentrations where heavily doped regions (10^19 to 10^21 atoms/cm³) are positioned at contact portions to reduce transmission loss through improved carrier concentration, while medium doped slab portions (10^17 to 10^19 atoms/cm³) maintain appropriate thickness for light confinement. This local differentiation allows minimal slab thickness for small bending radii while compensating for transmission loss through strategic heavy doping at contact regions.
3Stability of the object's composition
If the slab thickness is reduced to achieve significant light confinement, then light confinement is improved, but resistance increases which reduces phase shifter speed
Solution Approach 1:
The waveguide structure achieves strong light confinement through reduced slab thickness while maintaining low resistance by implementing a three-tier doping strategy: heavily doped contact portions (10^19 to 10^21 atoms/cm³) to ensure low contact resistance, medium doped slab portions (10^17 to 10^19 atoms/cm³) to maintain electrical performance, and lightly doped waveguide portions (10^16 to 10^18 atoms/cm³) to preserve phase shifter speed. This local quality differentiation resolves the contradiction between light confinement and phase shifter speed.
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 structure achieves improved bandwidth and speed with reduced contact resistance and transmission loss, enabling smaller bending radii for phase shifters, facilitating the design of serpentine-shaped phase shifters.
Implementation Method 1
Applying an electrical field to the p-n, or p-i-n, junction can form depletion and accumulation/injection regions. The optical refractive index of such a phase shifting portion varies depending on carrier concentration, e.g. depletion or accumulation, inducing a phase shift to the light propagating in the waveguide through the phase shifting portion.
Data Source
AI summary
An optical phase-shifting device includes a ribbed waveguide portion on an insulating layer, the waveguide portion having a p-n or p-i-n junction extending in a longitudinal direction and having a height. A pair of slab portions are disposed adjacent the waveguide portion, one on each side of the ribbed waveguide portion and on the insulation layer. The slab portion have higher doping concentrations than the respective doping concentrations in the ribbed waveguide portion. At least a portion of each slab portion has a height increasing with distance from the waveguide portion, with the slab height being smaller than that of the waveguide portion at the junction between the waveguide portion and slab portion. A pair of contact portions are formed adjacent the respective slab portion and further away from the waveguide portion. A portion of each contact portion can also have a height varying with distance from the waveguide portion.