Structured Mirror Fiber Coupling for Low-Profile Grating Couplers
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Solution Overview
Problem
Existing methods for coupling optical fibers to photonic integrated circuits (PICs) face challenges in tolerance, manufacturability, ease of use, functionality, and cost, particularly with quartz fiber arrays and angled polished fibers, which are expensive and complicate the alignment process.
Innovation Solution
A novel optical connector using a mirror to orient the optical fiber axis at small angles parallel to the PIC surface, integrated with a structured reflective surface and alignment groove, formed by precision stamping, to achieve precise alignment and low-profile coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If quartz fiber arrays are used to position optical fibers, then the fibers can be positioned on standard pitch, but the tolerances are greater than 1 micrometer which is not ideal for single-mode applications and the arrays are expensive to manufacture
Solution Approach 1:
The patent replaces expensive, precision-ground quartz fiber arrays with inexpensive plastic ferrules that can be easily manufactured. The plastic ferrules achieve sufficient alignment tolerance (better than 1 micrometer) for single-mode applications without requiring costly CNC machining processes, thereby reducing manufacturing costs while maintaining or improving alignment precision.
Solution Approach 2:
The patent changes the material parameter from quartz to plastic, and the manufacturing method from CNC grinding to injection molding or similar low-cost processes. This parameter change enables mass production of fiber positioners with consistent sub-micrometer tolerance at fraction of the cost of quartz arrays.
2Reliability
If angled polished optical fibers are used with grating couplers, then the mode field can be matched to the design angle, but this adds another level of complication to the alignment process
Solution Approach 1:
The patent extracts the angular correction function from the fiber end-face polishing process and relocates it to a separate prism element. This allows the fiber itself to remain simple and straight (easier to handle and align), while the prism provides the necessary angular transformation to match the grating coupler's design angle, thereby reducing overall system complexity.
Solution Approach 2:
The patent introduces a prism as an intermediary element between the optical fiber and the grating coupler. The prism mediates the angular mismatch by transforming the propagation direction of light, enabling mode field matching without requiring angled fiber polishing, thus simplifying the alignment process while maintaining coupling efficiency.
3Productivity
If optical fibers are butt-coupled normal to the flat surface of the PIC using grating couplers, then the PICs can be tested prior to dicing using probers, but the quartz fiber array and bend radius adds to the height of the packaged PIC
Solution Approach 1:
The patent reorients the optical fiber from a vertical arrangement (perpendicular to the PIC surface) to a horizontal arrangement (parallel to the PIC surface). This dimensional change allows the fiber to bypass the height constraint imposed by the PIC thickness and packaging, enabling wafer-level testing while reducing the overall packaged height by eliminating the need for vertical fiber extension and bending space.
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 solution provides improved tolerance, manufacturability, ease of use, and reduced costs while maintaining high reliability and functionality, allowing for efficient optical coupling with existing grating couplers.
Implementation Method 1
a mirror to turn light to/from the optical fiber
Data Source
AI summary
An optical coupling between an optical fiber and a grating coupler having a design angle, in the form of an optical bench having a structured reflective surface at which incident light is directed. The optical bench supports the optical fiber in optical alignment with respect to the structured reflective surface. The optical fiber is a single-mode fiber. The structured reflective surface turns light transmitted between the grating coupler and the optical fiber and includes a three-dimensional concave reflective surface profile that is structured to reshape the light transmitted between the grating coupler and the optical fiber to produce a mode field that matches the optical fiber input/output and the design angle of the grating coupler.