Kinematic Chip-to-Chip Bonding for Optical Alignment
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Solution Overview
Problem
The alignment of optical fibers and waveguides in integrated photonics is challenging due to their small dimensions and different refractive indices, leading to misalignment and significant insertion losses during coupling, especially when aligning two substrates with 6 degrees of freedom in three-dimensional space.
Innovation Solution
The use of kinematic pins and sockets with sloping sides on the substrates allows for precise alignment in the X-Y plane, combined with standoffs for Z-direction control, enabling accurate positioning of optical fibers relative to waveguides, and the use of a wafer bonding tool for further alignment accuracy, exceeding the limitations of conventional alignment techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional alignment techniques are used for coupling optical fibers and waveguides, then the alignment process is simple, but misalignment occurs leading to significant insertion losses
Solution Approach 1:
The patent introduces an intermediary alignment mechanism consisting of kinematic pins and sockets that mediate between the optical fiber and waveguide. The pins are positioned in the optical fiber and the sockets in the waveguide, serving as intermediate reference elements that enable precise alignment without direct contact between the fiber and waveguide, thereby achieving sub-micron alignment precision while managing system complexity
Solution Approach 2:
The patent replaces conventional mechanical alignment systems with a kinematic constraint system. Instead of using complex mechanical stages and adjustment mechanisms, the invention uses a set of pins and sockets that create kinematic constraints, allowing the optical fiber and waveguide to self-align through controlled degrees of freedom, thus reducing mechanical complexity while improving alignment precision
2Productivity
If the dimensions of waveguides are reduced to increase integration density, then more components can be integrated, but alignment becomes more difficult due to smaller tolerances
Solution Approach 1:
The patent transitions the alignment problem from a two-dimensional plane to a three-dimensional kinematic constraint system. By using pins with specific diameters and sockets with corresponding dimensions, the alignment is achieved through dimensional constraints in multiple directions, enabling precise positioning even as waveguide dimensions are reduced for higher integration density
Solution Approach 2:
The patent changes the alignment parameters from direct fiber-to-waveguide dimensional matching to a pin-socket constraint system. The pin diameter, socket dimensions, and their positional relationships are carefully controlled parameters that enable sub-micron alignment precision, allowing the system to maintain high manufacturing precision even as waveguide dimensions are reduced to increase integration density
Data Source
AI summary
The various technologies presented herein relate to integrating an IC having at least one waveguide incorporated therein with a v-groove array IC such that an optical fiber located in a v-groove is aligned relative to a waveguide in the IC maximizing optical coupling between the fiber and the waveguide. The waveguide IC and the v-groove array IC are bonded in a stacked configuration. Alignment of the waveguide IC and the array IC in the stacked configuration enables advantage to be taken of lithographic accuracy of features formed with respect to the Z-direction. Further, kinematic pins and sockets are utilized to provision accuracy in the X- and Z-directions, wherein advantage is taken of the placement accuracy and fabrication tolerance(s) which can be utilized when forming the and sockets. Accordingly, automated alignment of the waveguide IC and the array IC is enabled, facilitating accurate alignment of the respective waveguides and fibers.