Asymmetric Optical Power Splitter with Adiabatic Taper
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Solution Overview
Problem
Existing optical splitters are sensitive to fabrication variations and physical symmetry, leading to high loss, back reflection, and limited tolerance to layer thickness changes, which affects their performance and reliability in applications like Mach-Zehnder interferometers.
Innovation Solution
The design employs adiabatic mode evolution with a gap between output waveguides, allowing for electrical isolation and reduced sensitivity to fabrication variations, using a taper to transition the dominant mode from a singly peaked to a doubly peaked mode without requiring physical symmetry along the device length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional symmetric Y-splitter design is used, then fabrication process is simple, but the device is highly sensitive to fabrication variations and layer thickness changes
Solution Approach 1:
The patent applies asymmetry by designing an asymmetric Y-splitter architecture where the input waveguide is positioned offset from the centerline of the output waveguides. This asymmetric configuration intentionally breaks the symmetry that characterizes traditional Y-splitters, making the device performance less sensitive to fabrication variations and layer thickness changes. The asymmetric design allows the optical mode to evolve adiabatically through the taper region without requiring precise symmetric alignment, thereby improving reliability against manufacturing tolerances.
2Loss of energy
If adiabatic mode evolution with gap is used, then loss and back reflection are reduced, but device length increases
Solution Approach 1:
The patent applies partial action by implementing a tapered region that provides adiabatic mode evolution over a extended length, but only in the critical transition zone where mode transformation occurs. The taper gradually transforms the optical mode from the input waveguide to the output waveguides, reducing loss and back reflection. By concentrating the adiabatic transformation in a dedicated tapered section rather than extending it throughout the entire device, the design achieves low loss while controlling overall device length.
3Reliability
If output waveguides are physically connected, then device structure is compact, but electrical isolation between outputs is lost
Solution Approach 1:
The patent applies segmentation by introducing a gap that physically separates the output waveguides, dividing what would otherwise be a continuous structure into distinct segments. This gap provides electrical isolation between the output waveguides, preventing electrical crosstalk while allowing optical mode evolution through the tapered region. The segmented design maintains optical functionality while achieving the desired electrical isolation, with the gap acting as both an electrical barrier and a structural feature that enables adiabatic mode transformation.
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 approach results in low loss, low back reflection, a large operating bandwidth, and high tolerance to fabrication variations, ensuring a stable 3-dB split ratio even with significant layer thickness changes, and provides electrical isolation between output waveguides.
Implementation Method 1
Each of the output waveguides includes a taper to transition a singly peaked dominant mode of light launched into the input waveguide into a doubly peaked mode
Data Source
Figure 1A~1E
Figure 1F~1H
Figure 2
AI summary
Embodiments of the present disclosure include devices that split a light beam into two separate paths, with reduced sensitivity to fabrication variation. The devices can operate as 3-dB splitters that divide the input optical energy equally between two output waveguides. Similarly, the devices can also function to combine two light beams into a single path (coupler). The designs make use of adiabatic modal evolution and do not require physical symmetry along the entire device length. The devices inlcude first and second waveguides, each having a transition section, which may be tapered, the transition disposed adjacent to each other defining a gap therebetween, such that optical energy couples between the waveguides.