Edge-Coupled Hybrid Optical Source Alignment
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Solution Overview
Problem
The challenge in fabricating a hybrid optical source lies in achieving efficient light emission on silicon substrates due to silicon's poor light-emitting properties and the difficulties in integrating III-V compound semiconductors, which result in high optical coupling losses and alignment complexities, limiting the wall-plug efficiency and reliability of silicon-photonic links.
Innovation Solution
A method for fabricating a co-planar hybrid optical source using a temporary transparent substrate with alignment markers to align and couple III-V compound-semiconductor devices with silicon-on-insulator (SOI) chips, employing backside etching-assisted cleaving and spot-size converters to reduce alignment complexity and enable wafer-scale integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If surface-normal coupling with grating optical couplers is used, then optical coupling efficiency is improved, but device complexity and alignment precision requirements increase
Solution Approach 1:
The patent transitions from surface-normal coupling (vertical dimension) to edge-coupled co-planar integration (lateral dimension). This dimensional change allows optical waveguides from different substrates to be coupled horizontally at the same planar level, eliminating the need for vertical alignment through substrates and reducing alignment complexity while maintaining coupling efficiency.
Solution Approach 2:
The patent introduces a temporary transparent substrate as an intermediary carrier during the integration process. This temporary substrate provides a common reference plane for bonding III-V compound semiconductor and silicon substrates, enabling precise edge alignment through optical microscopy without requiring direct alignment between the final device components. The temporary substrate is removed after bonding, leaving the integrated device.
2Illumination intensity
If hybrid wafer integration of III-V compound semiconductors with silicon is used, then light emission efficiency is improved, but wall-plug efficiency deteriorates due to taper loss and thermal impedance
Solution Approach 1:
The patent adopts edge-coupled co-planar integration where optical waveguides from III-V and silicon substrates are coupled horizontally at the same planar level. This eliminates the need for tapered waveguide structures required in vertical evanescent coupling, reducing taper loss and improving wall-plug efficiency while maintaining effective light emission.
Solution Approach 2:
The patent creates a common reference plane by bonding both III-V and silicon substrates to the same temporary transparent substrate. This equipotential bonding approach ensures uniform thermal and mechanical characteristics across the hybrid structure, reducing thermal impedance and improving overall wall-plug efficiency.
3Loss of energy
If accurate alignment with submicron tolerances is used for edge-to-edge butt-coupling, then optical coupling efficiency is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent uses a temporary transparent substrate as a mediator that provides a common reference plane for both III-V and silicon substrates. Alignment markers on this temporary substrate enable optical microscopy alignment with relaxed tolerances (several microns) during bonding, eliminating the need for complex submicron alignment systems. The temporary substrate is removed after integration, leaving the aligned hybrid device.
Solution Approach 2:
The patent performs preliminary alignment by bonding both substrates to the temporary substrate with alignment markers before final integration. This preliminary alignment step establishes the correct relative positioning early in the process, allowing subsequent steps to proceed without requiring high-precision alignment equipment, thereby reducing manufacturing 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 simplifies the alignment process, enables high-yield, low-cost, and high-performance hybrid optical sources, facilitating efficient optical interconnects for applications like high-performance computing by reducing optical coupling losses and improving integration efficiency.
Implementation Method 1
a temporary transparent substrate with alignment markers is disposed on a first optical device
Implementation Method 2
alignment markers are aligned with a first optical waveguide in the first optical device
Data Source
AI summary
A technique for fabricating a hybrid optical source is described. During this fabrication technique, a III-V compound-semiconductor active gain medium is integrated with a silicon-on-insulator (SOI) chip (or wafer) using edge coupling to form a co-planar hybrid optical source. Using a backside etch-assisted cleaving technique, and a temporary transparent substrate with alignment markers, a III-V compound-semiconductor chip with proper edge polish and coating can be integrated with a processed SOI chip (or wafer) with accurate alignment. This fabrication technique may significantly reduce the alignment complexity when fabricating the hybrid optical source, and may enable wafer-scale integration.