Overlying Waveguide Taper for Optical Coupling
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Solution Overview
Problem
Current methods for coupling radiation between optical integrated circuits and optical fibers face challenges due to mode size mismatches, leading to high coupling losses and complex, costly fabrication processes, especially when using standard single-mode fibers.
Innovation Solution
The development of an optical device with a semiconductor die featuring an integrated optical waveguide and an overlying waveguide taper with a facet, which allows for efficient coupling with a small footprint and low-cost wafer-scale manufacturing, using a polymer waveguide and index-matching materials to minimize alignment sensitivity and coupling losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mode-size converter using an SOI inverted taper with an overlying waveguide is used, then coupling between special optical fiber and SOI chip is achieved, but coupling to standard fiber with low loss is not possible due to large mode mismatch
Solution Approach 1:
The patent introduces a vertical dimension by placing an overlying waveguide above the integrated waveguide core, creating a three-dimensional structure. This vertical arrangement allows the overlying waveguide to serve as an intermediate mode converter, bridging the mode size difference between the integrated waveguide and standard optical fiber without requiring lateral dimension changes alone.
Solution Approach 2:
The overlying waveguide acts as an intermediary element between the integrated waveguide core and the optical fiber. It receives radiation from the integrated waveguide through evanescent coupling and transfers it to the fiber, mediating the mode size transformation and enabling compatibility with standard fibers.
2Reliability
If special optical fibers such as lensed fiber or small core fiber are used, then coupling to integrated waveguide is achieved, but precise alignment is required increasing complexity
Solution Approach 1:
The overlying waveguide's dimensions, particularly its width and height, are optimized to create a mode field that matches standard single-mode fiber parameters. By controlling the waveguide geometry parameters, the system achieves compatibility with standard fiber while maintaining loose alignment tolerances.
3Ease of manufacture
If underlying waveguide based on buried oxide is used, then mode-size transformation is achieved, but minimal theoretical loss of at least 3 dB occurs
Solution Approach 1:
The patent combines the advantages of both underlying and overlying waveguide structures by integrating an overlying waveguide that works in conjunction with the buried oxide layer. This merged structure enables mode transformation with lower loss by providing dual pathways for evanescent coupling.
4Reliability
If three-dimensional silicon tapers are used, then coupling between integrated waveguide and standard fiber is achieved, but complex manufacturing steps such as deposition of thick amorphous silicon and grayscale etching are required
Solution Approach 1:
The overlying waveguide can be fabricated using simpler, more cost-effective processes compared to three-dimensional silicon tapers. The structure uses standard semiconductor fabrication techniques without requiring complex steps like grayscale etching or thick amorphous silicon deposition, making it more suitable for mass production.
5Loss of energy
If grating couplers are used, then relatively low coupling losses are achieved, but operation is restricted to limited bandwidth
Solution Approach 1:
The overlying waveguide structure provides broadband operation capability, making it suitable for multiple wavelength applications. Unlike grating couplers that are wavelength-specific, this structure maintains efficient coupling across a broad spectral range, enabling universal application in different optical communication bands.
6Productivity
If wafer is cut into individual dice using dicing saw, then individual circuits are obtained, but rough facet is created requiring delicate and expensive facet polishing
Solution Approach 1:
The overlying waveguide is designed with its facet positioned at a specific distance from the wafer edge before dicing. This preliminary positioning ensures that after wafer cutting, the waveguide facet remains intact and properly exposed without requiring additional polishing steps, as the structure was pre-configured to accommodate the dicing process.
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 solution achieves high coupling efficiency across a broad wavelength range with reduced alignment sensitivity and eliminates the need for facet polishing, enabling efficient and cost-effective coupling between optical waveguides and fibers.
Implementation Method 1
an optical device with a semiconductor die featuring an integrated optical waveguide and an overlying waveguide taper with a facet, which allows for efficient coupling with a small footprint
Implementation Method 2
an overlying waveguide comprising a waveguide taper and a waveguide facet. The overlying optical waveguide at least partially overlies the integrated optical waveguide core
Data Source
AI summary
Disclosed are optical devices for coupling radiation between an optical waveguide and an external medium. In one embodiment, an optical device is disclosed comprising a semiconductor die comprising an integrated optical waveguide core and an overlying optical waveguide comprising a waveguide taper and a waveguide facet. The overlying optical waveguide at least partially overlies the integrated optical waveguide core, and the waveguide facet is between about 1 μm and 200 μm from an edge of the semiconductor die. In another embodiment, a method is disclosed comprising providing a substrate comprising an integrated semiconductor waveguide and forming on the substrate an overlying waveguide comprising a waveguide taper and a waveguide facet. The overlying waveguide at least partially overlies the integrated semiconductor waveguide. The method further includes cutting the substrate about 1 μm and 200 μm from the waveguide facet.