Rib-Type Waveguide 90-Degree Hybrid Circuit
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Solution Overview
Problem
Conventional 90-degree hybrid circuits using four optical couplers and channel-type bending waveguides are highly susceptible to phase errors due to manufacturing variations, affecting their performance.
Innovation Solution
The optical semiconductor device employs a configuration with rib-type single mode waveguides and MMI couplers, which reduces the impact of manufacturing variations by minimizing the influence of waveguide width and thickness fluctuations, and includes a slab portion structure to minimize mode coupling and radiation loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If channel-type bending waveguides are used in 90-degree hybrid circuits, then the device can be manufactured with conventional processes, but the circuit becomes highly susceptible to phase errors due to manufacturing variations in waveguide width and thickness
Solution Approach 1:
The patent changes the waveguide cross-sectional parameters from channel-type to rib-type structure, where the rib portion extends in the vertical direction. This parameter change makes the waveguide mode less sensitive to width and thickness variations, thereby reducing phase errors while maintaining manufacturability through standard semiconductor fabrication processes
Solution Approach 2:
The patent introduces a slab portion with different refractive index characteristics than the rib portion, creating local quality variations within the waveguide structure. The slab portion serves as a low-index region that confines the optical mode effectively, making the overall waveguide performance less sensitive to dimensional variations in the rib portion
2Device complexity
If conventional optical couplers are used, then the device structure is simpler, but phase errors occur due to manufacturing variations affecting waveguide dimensions
Solution Approach 1:
The patent modifies the waveguide structural parameters by introducing rib-type waveguides with extended vertical profiles and slab portions. These parameter changes result in mode confinement that is less sensitive to manufacturing variations, thereby improving phase stability without significantly increasing device complexity
Solution Approach 2:
The slab portion acts as a cushioning element that compensates for the effects of manufacturing variations. By providing a controlled low-refractive-index region, the slab portion beforehand cushions against the adverse effects of width and thickness variations, maintaining stable phase characteristics
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
This configuration significantly reduces phase errors and maintains high transmittance, making the optical semiconductor device more resistant to manufacturing variations and improving its overall performance.
Implementation Method 1
a 90-degree hybrid circuit is a circuit that separates, by causing phase-modulated signal light and local oscillator (LO) light to interfere with each other, the signal light into I-axis components and Q-axis components
Implementation Method 2
a first single mode waveguide configured to connect the second input port and the third output port
Data Source
AI summary
An optical semiconductor device includes a first optical coupler including a first input port and a second input port, a first optical branching device including a first output port and a second output port, a second optical coupler including a third input port and a fourth input port, a second optical branching device including a third output port and an fourth output port, a first single mode waveguide configured to connect the second input port and the first output port, a second single mode waveguide configured to connect the second output port and the third input port, a third single mode waveguide configured to connect the fourth input port and the third output port, and a fourth single mode waveguide configured to connect the fourth output port and the first input port.