Semiconductor Waveguide Spot Size Converter for Fiber Coupling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing semiconductor optical waveguide devices face significant optical coupling losses due to the mismatch in the half-width of light distribution between semiconductor optical waveguides and single-mode optical fibers, which is exacerbated by the need for precise control of multiple mesa structures during manufacturing.
Innovation Solution
A semiconductor optical waveguide device is designed with a specific structure comprising multiple mesa layers, including a cladding layer, an intermediate layer, and core layers, where the widths of the mesa portions are carefully controlled to match the mode field diameter of the optical fiber, allowing for efficient optical coupling and modulation of light using electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a narrow semiconductor optical waveguide width (≤2 μm) is used to maintain fundamental transverse mode propagation, then optical mode confinement is achieved, but optical coupling loss to single-mode optical fiber increases due to mismatch with fiber mode field diameter (3-4 μm)
Solution Approach 1:
The patent transitions from two-dimensional lateral mode matching to three-dimensional vertical mode transformation. By stacking multiple semiconductor layers with different refractive indices and widths in the vertical direction, the invention creates a spot size converter that transforms the optical mode field diameter from narrow (≤2 μm) at the waveguide core to wider (3-4 μm) at the fiber coupling interface, resolving the coupling loss problem while maintaining mode confinement in the propagation direction
Solution Approach 2:
The invention changes the geometric parameters of the optical waveguide structure by creating a tapered or expanded region in the spot size converter. The semiconductor layers are designed with varying widths and thicknesses, transitioning from a narrow core region to a wider output region, thereby changing the mode field diameter parameter to match the optical fiber's mode field diameter and reduce coupling loss
2Loss of energy
If multiple waveguide mesas with different widths are formed to achieve spot size conversion, then optical coupling efficiency improves, but manufacturing complexity and precision requirements increase
Solution Approach 1:
The patent divides the optical waveguide structure into multiple functional segments stacked vertically: a lower waveguide mesa for mode confinement, an intermediate spot size converter region with gradually varying dimensions, and an upper waveguide mesa for fiber coupling. This segmentation allows each layer to be optimized independently while maintaining overall manufacturing feasibility through standard epitaxial growth and mesa formation processes
Solution Approach 2:
The spot size converter structure is designed and formed in advance during the epitaxial growth process, with pre-determined layer thicknesses and widths that automatically provide the required mode field transformation. This preliminary structuring eliminates the need for complex post-processing to achieve precise width control, as the dimensional transitions are built into the semiconductor layers themselves
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 enhances optical coupling efficiency and stabilizes optical waveguiding by ensuring that the mode field diameter of the semiconductor waveguide matches that of the external fiber, reducing reflection and improving modulation characteristics.
Implementation Method 1
optical propagation in a fundamental transverse mode through the optical waveguide
Implementation Method 2
the spot size converter performs transition of guided light from one of the optical waveguide structures to another optical waveguide structure in the stacking direction
Implementation Method 3
Light propagating through the core layer can be modulated by applying an electrical signal to the core layer using an electrode
Data Source
AI summary
A semiconductor optical waveguide device includes a substrate having a first area and a second area, and first, second, and semiconductor mesas on the substrate. The first semiconductor mesa includes a cladding layer and a first mesa portion on the second area, the first mesa portion including first and second portions. The second semiconductor mesa includes an intermediate layer, a first core layer, and first and second mesa portions on the first and second areas, respectively. The third semiconductor mesa includes a second core layer, and first and second mesa portions having a greater width than that of the second semiconductor mesa. The first portion of the first semiconductor mesa has a substantially same width as the second mesa portion of the second semiconductor mesa. The first core layer is optically coupled to the second core layer through the intermediate layer disposed between the first and second core layers.