Photonic Die Alignment Using Tilted Waveguides
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Solution Overview
Problem
Current photonic die alignment techniques face challenges in achieving high coupling efficiency and low back reflection, particularly when integrating light sources or gain media from disparate substrates, due to limitations in alignment accuracy and material compatibility, which can lead to misalignment and reduced lasing stability.
Innovation Solution
The use of tilted coupling waveguides and alignment features, such as grooves and curved protrusions, enables precise passive alignment with high tolerance for fabrication errors, constraining movement along multiple axes, and reduces back reflection by optimizing the alignment of photonic dies with tilted waveguides, facilitating integration of external gain media like RSOAs into PIC systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional alignment techniques are used for photonic die integration, then the alignment process is simpler, but alignment accuracy deteriorates leading to misalignment and reduced coupling efficiency
Solution Approach 1:
The patent changes the geometric parameters of alignment features by tilting them relative to the die edge. The tilt angle is specifically designed to compensate for fabrication errors, transforming the alignment system from one that requires perfect perpendicularity to one that is inherently tolerant of edge formation variations. This parameter change enables sub-micron alignment accuracy while maintaining robustness against manufacturing variations.
Solution Approach 2:
The patent introduces asymmetric alignment features with specific tilt angles that are not symmetric with respect to the die edge. This asymmetry is deliberately designed to counteract the symmetric nature of fabrication errors, creating a compensation mechanism that achieves high alignment accuracy. The asymmetric geometry allows the alignment features to converge to the correct position despite edge formation variations.
2Object-generated harmful factors
If perpendicular coupling waveguides are used, then the waveguide design is simpler, but back reflection increases reducing lasing stability
Solution Approach 1:
The patent changes the orientation parameter of coupling waveguides from perpendicular (90 degrees) to a tilted angle. This parameter change reduces back reflection by optimizing the coupling interface geometry. The specific tilt angle is chosen to minimize reflected light while maintaining effective coupling, thereby improving lasing stability without requiring complex additional components.
3Manufacturing precision
If high alignment accuracy is achieved through active alignment, then coupling efficiency improves, but the integration process becomes more complex and time-consuming
Solution Approach 1:
The patent performs preliminary action by pre-tilting the alignment features and waveguides during fabrication to anticipate and compensate for expected fabrication errors. This preliminary geometric configuration eliminates the need for complex active alignment procedures during integration, as the features are pre-configured to align correctly despite manufacturing variations. This approach maintains sub-micron alignment accuracy while dramatically simplifying and accelerating the integration process.
Solution Approach 2:
The patent enables self-service alignment where the tilted geometric features automatically compensate for their own fabrication errors. The alignment system is self-correcting, using the tilt geometry to naturally converge to the correct position without requiring external active alignment mechanisms. This self-aligning property achieves high precision while maintaining fast integration speeds.
Data Source
AI summary
A first photonic die has a first coupling edge and a first die surface, and comprises: a first waveguide extending in proximity to the first coupling edge; a portion of the first die surface forming an alignment edge substantially parallel to the first waveguide; and a first alignment feature etched into or formed adjacent to the first coupling edge. A second photonic die has a second coupling edge and a second die surface, and comprises: a second waveguide extending in proximity to the second coupling edge; a portion of the second die surface configured to form a receptacle sized to constrain a position of the alignment edge; and a second alignment feature etched into or formed adjacent to the second coupling edge and configured to enable alignment with the first alignment feature when the first photonic die and the second photonic die are substantially aligned with each other.