Trench Lens Optical Coupling for Silicon Waveguide Mounting
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Solution Overview
Problem
Existing optical devices face challenges in reducing coupling loss between silicon waveguides and optical fibers due to mode field mismatches, and they require complex mounting processes that increase man-hours, especially when using lenses to match mode fields.
Innovation Solution
An optical device with a trench on the substrate, where the optical waveguide is connected to one side of the trench and a lens is arranged inside the trench, allowing the optical fiber to be secured to the adjacent side surface using an adhesive, thereby enabling both optical coupling and fixation while reducing the number of man-hours needed for mounting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a lens is arranged between the Si waveguide and the optical fiber to match mode fields, then coupling loss is reduced, but the mounting process becomes complex and requires more man-hours
Solution Approach 1:
The patent combines the optical coupling function (lens) and the fixation function (mounting structure) into a single integrated component. The lens is formed directly on the waveguide end surface within a trench structure, eliminating the need for separate lens mounting and fiber alignment steps. This merging of functions reduces mounting complexity while maintaining low coupling loss.
Solution Approach 2:
The lens is pre-formed on the waveguide end surface during the fabrication process before final assembly. The trench structure is also prepared in advance, creating a predetermined positioning feature that guides the optical fiber into correct alignment. This preliminary preparation eliminates the need for complex real-time alignment during mounting.
2Loss of energy
If the waveguide width is reduced to increase mode field and reduce coupling loss, then coupling loss decreases, but the waveguide becomes more difficult to manufacture with standard CMOS processes
Solution Approach 1:
The waveguide maintains a standard width along most of its length for easy CMOS manufacturing, but the width is locally reduced only at the end surface where the lens is formed. This localized modification allows the waveguide to be manufactured with standard processes while still achieving the necessary mode field matching at the coupling interface.
Solution Approach 2:
Instead of reducing waveguide width in one dimension throughout the entire structure, the invention addresses the coupling issue by modifying the optical properties in another dimension - adding a lens structure that extends perpendicular to the waveguide surface. This dimensional approach allows mode field matching without compromising manufacturing ease.
3Ease of operation
If the optical fiber is mounted directly on the chip end surface, then the mounting process is simple, but coupling loss increases due to mode field mismatch
Solution Approach 1:
The lens formed on the waveguide end surface acts as an intermediary between the waveguide and the optical fiber. It mediates the mode field mismatch by transforming the waveguide mode into a mode that better matches the fiber mode, enabling efficient coupling while maintaining a simple direct mounting structure.
Solution Approach 2:
The coupling interface is segmented into distinct functional zones: the trench region containing the lens for optical coupling, and the adjacent bonding region for mechanical fixation. This segmentation allows the optical fiber to be mounted directly on the chip surface in a simple process while the lens separately handles the optical coupling function.
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
This configuration effectively suppresses coupling loss between the optical fiber and silicon waveguide while simplifying the mounting process by integrating optical coupling and fixation, thus improving efficiency and reducing the time required for assembly.
Implementation Method 1
a lens 16 that is arranged on the first side surface included in the trench 15 and is connected to the optical waveguide 13
Data Source
AI summary
An optical device includes a substrate, a trench that is formed on the substrate, an optical waveguide that is formed on the substrate and that is connected to a first side surface of the trench, and a lens that is arranged on the first side surface included in the trench and that is connected to the optical waveguide. Furthermore, the optical device includes an optical fiber that is secured, by an adhesive, to a chip end surface that is located adjacent to a second side surface that is located opposite the first side surface included in the trench.