Angled Cavity Waveguide Alignment for High Density Photonics
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Solution Overview
Problem
Conventional v-groove alignment techniques for glass core fiber-to-silicon waveguide alignment in photonics integrated circuits face limitations with increasing waveguide density and reduced pitch, leading to reduced throughput and sensitivity to debris and cleaning issues.
Innovation Solution
A passive alignment mechanism using trench formations and alignment structures on the fiber array unit interacting with the PIC die, eliminating the need for multiple v-grooves and allowing for non-uniform pitch scaling and increased waveguide density, with alignment features farther away from waveguides to reduce sensitivity to debris and improve uniformity of the index matching epoxy bond-line thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If v-grooves are used for waveguide alignment, then alignment is achieved, but manufacturing throughput is reduced and the system becomes sensitive to debris and cleaning issues
Solution Approach 1:
The alignment function is segmented into two independent parts: a cavity in the PIC die and a corresponding protrusion in the fiber array unit. This segmentation allows each component to be manufactured separately with standard processes, eliminating the need for complex v-groove formation and improving manufacturing throughput while maintaining alignment reliability.
Solution Approach 2:
The alignment features (cavity and protrusion) are extracted from the waveguide structure itself and placed as separate elements. This extraction removes the sensitivity to debris and cleaning issues that plague v-groove systems, as the alignment features are now distinct, robust structures that can be manufactured with standard tolerances.
2Reliability
If v-grooves are used for waveguide alignment, then alignment is achieved, but the system is sensitive to debris and cleaning issues
Solution Approach 1:
The cavity and protrusion design provides inherent robustness against debris before assembly occurs. The interlocking nature of the cavity-protrusion interface prevents debris from interfering with alignment, as the features are designed to mate precisely without requiring the clean, open geometry of v-grooves. This beforehand cushioning eliminates sensitivity to contamination.
3Quantity of substance
If waveguide density is increased and pitch is reduced, then more waveguides can be integrated, but v-groove alignment becomes limited due to fiber diameter and reduced throughput
Solution Approach 1:
The invention changes the geometric parameters of the alignment features (cavity depth, protrusion height, interface dimensions) to optimize for high-density waveguide arrays. These parameter adjustments allow the alignment mechanism to function effectively at reduced pitch and increased density without compromising manufacturing throughput, as the features can be formed with standard processes.
4Reliability
If multiple v-grooves are formed in the PIC die, then waveguide alignment is achieved, but the device complexity increases
Solution Approach 1:
The alignment function is merged into the bonding interface itself through the cavity-protrusion design. Instead of requiring separate, complex v-groove structures in the PIC die, the alignment features are integrated as simple complementary geometries that mate during assembly. This merging reduces device complexity while maintaining reliable waveguide alignment.
Data Source
AI summary
In one embodiment, a device includes a fiber array unit (FAU) coupled to a photonics integrated circuit (PIC) die. The PIC die includes a cavity defined at an edge of the PIC die, with outer edges of the cavity being formed at an angle less than 90 degrees with respect to a bottom surface of the cavity. The PIC die further includes first waveguides protruding into the cavity of the PIC die. The FAU includes a shelf portion extending from a body portion, and a plurality of second waveguides protruding from an outer edge of the shelf portion opposite the body portion. The FAU further includes alignment structures on outer edges of the shelf portion that are in contact with the angled edges of the cavity of the PIC die.