Optical Interposer Waveguide Structure for Robust PIC Coupling
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Solution Overview
Problem
Existing methods for optically connecting different photonic integrated circuits (PICs) face challenges such as complex design, hard-to-fabricate couplings, mechanical fragility, contamination susceptibility, and limited coupling efficiency, particularly in hybrid integration techniques like flip-chip and direct butt-coupling, and photonic wire bonds.
Innovation Solution
An optical interposer using a microstructured or graded-index waveguide with a core-cladding configuration and support structures, enabling robust and efficient hybrid integration of PICs through active alignment, allowing for various waveguide types and flexible routing, including 3D bends and tapered ends, with optional V-grooves and lenses for alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If direct butt-coupling approach is used to connect two PICs, then optical coupling efficiency can be maximized, but complex custom spot-size converters are required that take up large chip area and are hard to fabricate
Solution Approach 1:
The patent introduces a separate coupling component (interposer) that mediates between the two PICs. This interposer contains waveguides with optimized mode fields that couple to both PIC types, eliminating the need for complex custom spot-size converters on the PICs themselves. The coupling component acts as an intermediary that handles the mode matching complexity externally.
Solution Approach 2:
The patent segments the coupling function into a separate, standalone component rather than integrating it directly into the PICs. This segmentation allows the coupling optimization to be decoupled from the PIC design, enabling standard PIC fabrication processes to be used while achieving optimized coupling through the separate interposer component.
2Adaptability or versatility
If flip-chip design with vertical coupling is used, then integration of two PICs is achieved, but complex design with integrated mirrors and gratings is required
Solution Approach 1:
The coupling interposer serves as an intermediary that enables vertical coupling between PICs without requiring the PICs themselves to contain complex mirrors and gratings. The interposer incorporates the necessary optical coupling structures, simplifying the PIC design while maintaining integration capability.
Solution Approach 2:
The patent creates a universal coupling platform that can interface with multiple types of PICs using standard waveguide configurations. This universal interposer design eliminates the need for custom complex coupling structures for each PIC type, providing a multi-functional solution that works across different PIC platforms.
3Reliability
If photonic wire bonds with passive alignment are used, then permanent interconnections between chips and fibers are enabled, but alignment tolerances are very tight (sub-micrometer) and coupling efficiency is limited
Solution Approach 1:
The coupling component acts as an intermediary that provides alignment tolerance compensation between chips and fibers. By incorporating alignment features and tolerance-absorbing structures in the interposer, the system achieves reliable permanent interconnections without requiring sub-micrometer alignment precision.
Solution Approach 2:
The patent employs flexible coupling structures in the interposer that can accommodate alignment variations. These flexible elements allow for passive alignment with relaxed tolerances while still achieving reliable optical connections, eliminating the need for tight sub-micrometer alignment precision.
4Ease of manufacture
If photonic wire bonds with air-cladded waveguide configuration are used, then interconnections are achieved, but contamination of guided core and light leakage occur
Solution Approach 1:
The patent replaces the air-cladded waveguide configuration with a solid-clad waveguide structure. This creates an inert, protected environment for the optical core that prevents contamination from the external environment and eliminates light leakage, while maintaining ease of manufacture through standard fabrication processes.
Solution Approach 2:
The patent uses composite waveguide structures with distinct core and cladding materials. This composite design provides both mechanical protection and optical confinement, preventing contamination and light leakage while allowing for straightforward fabrication using conventional materials and processes.
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
The optical interposer provides reliable, mechanically robust connections with high coupling efficiency, supporting diverse PIC types and fiber configurations, reducing contamination risks and minimizing optical losses.
Implementation Method 1
focusing a laser beam in the two-photon polymerizable material so as to induce two-photon polymerization of part of the two-photon polymerizable material, so as to form an interposer waveguide
Data Source
AI summary
An optical interposer is for optically interconnecting a first optical waveguide with a second optical waveguide. The optical interposer includes: an interposer waveguide having a first end for optically connecting to the first optical waveguide and a second end for optically connecting to the second optical waveguide. The interposer waveguide is one of or a combination of a microstructured optical waveguide and graded-index optical waveguide, an interposer substrate, and at least one support structure rigidly connecting the interposer waveguide to the interposer substrate, so as to form a rigid, self-sustaining optical interposer.