Wafer-Scale Photonic Circuit Testing via Horizontal Spot-Size Converters
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Solution Overview
Problem
Current methods for coupling photonic integrated circuits (PICs) with single-mode optical fibers face challenges such as high loss due to mode-size mismatch and require dicing of the wafer for spot-size converters, making wafer-scale testing inefficient and costly, and grating couplers suffer from wavelength dependence and polarization dependency.
Innovation Solution
The use of a combination of grating couplers and horizontal spot-size converters, including deep trench etches and index matching fluids, allows for efficient out-of-plane fiber-to-waveguide coupling on a wafer, enabling wafer-scale testing without dicing, with optimized coupling efficiency and reduced loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If horizontal spot-size converters are used for fiber-to-waveguide coupling, then coupling efficiency is improved, but wafer dicing is required which reduces productivity
Solution Approach 1:
The invention segments the wafer into multiple independently testable circuits using deep trench etches that create isolated test regions. Each circuit can be tested separately with fiber arrays coupled to spot-size converters at the wafer edge, eliminating the need to dice the entire wafer while maintaining high coupling efficiency.
Solution Approach 2:
The invention introduces spot-size converters as intermediary structures at the wafer edge that bridge the mode-size mismatch between optical fibers and waveguides. These converters enable efficient out-of-plane coupling without requiring wafer dicing, serving as a mediator between the fiber coupling system and the integrated circuits.
2Productivity
If grating couplers are used for fiber coupling, then wafer-scale testing is enabled, but wavelength dependence and polarization dependency increase
Solution Approach 1:
Instead of using grating couplers that couple light in/out of plane with wavelength and polarization sensitivity, the invention inverts the approach by using horizontal spot-size converters that maintain in-plane propagation. This inverted coupling method achieves wafer-scale testing capability while eliminating wavelength and polarization dependency.
3Measurement precision
If deep trench etches are used to isolate circuits, then testing accuracy is improved, but device complexity increases
Solution Approach 1:
The deep trench etches serve multiple functions: they isolate individual circuits for independent testing, provide mechanical support for the waveguides, and create defined edges for fiber array coupling. This multi-functionality achieves high testing accuracy without proportionally increasing device complexity.
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 enables efficient and deterministic wafer-scale testing of photonic integrated circuits with reduced optical loss and polarization dependency, facilitating cost-effective and reliable testing of complete circuits before packaging.
Implementation Method 1
index matching fluids
Implementation Method 2
deep trench etches
Data Source
AI summary
Disclosed herein are methods, structures, and devices for wafer scale testing of photonic integrated circuits.