Self-Aligned Double U-Groove Optical Alignment Structure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High precision and cost are challenges in aligning optical fibers in optical transmitter modules due to large mode-mismatch loss and small numerical aperture, which complicates packaging and increases costs in high-density optical communication systems.
Innovation Solution
A silicon substrate with a 45-degree or 54.7-degree reflector and deeply etched double U-shape trenches is used to passively align optical fibers, combined with spacers for flip-chip bonding of light sources or photodetectors, reducing alignment complexity and increasing precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If micro-assembled microlens systems are used to reduce mode-size mismatch, then optical coupling efficiency is improved, but packaging complexity and cost increase
Solution Approach 1:
The patent extracts the microlens element from the packaging structure and integrates it directly into the substrate as an on-chip microlens. This eliminates the need for separate microlens components and their associated alignment mechanisms, thereby reducing packaging complexity while maintaining the optical focusing function that reduces mode-size mismatch loss.
Solution Approach 2:
The patent merges the microlens function with the substrate by forming an on-chip microlens structure that is monolithically integrated with the V-groove alignment features. This combining of functions into a single integrated structure simplifies the overall packaging while preserving the optical coupling efficiency benefits.
2Ease of manufacture
If self-aligned on-chip V-groove structures are used to relax alignment requirements, then packaging cost is reduced, but alignment precision is limited to a few micrometers
Solution Approach 1:
The patent implements a nested structure where the optical fiber is positioned within the V-groove, which itself is integrated with the on-chip microlens structure. This nested arrangement allows the fiber to be passively aligned by the V-groove geometry while the microlens provides additional optical focusing, achieving better than 1-micrometer alignment precision through the combined geometric constraints.
Solution Approach 2:
The V-groove structure is pre-formed on the substrate during semiconductor fabrication using standard lithography and etching processes. This preliminary formation of the alignment structure eliminates the need for subsequent active alignment steps, achieving high precision through the pre-defined geometric constraints of the grooves.
3Manufacturing precision
If precisely controlled etching time and rates are used to improve alignment accuracy, then alignment precision is improved, but manufacturing complexity increases
Solution Approach 1:
The patent changes the etching parameters by using isotropic etching chemistry (such as BOE or HF) that etches at uniform rates in all directions. This parameter change allows the V-groove depth and shape to be controlled by the etch time and chemistry rather than requiring complex anisotropic etching with precisely controlled angles, simplifying the manufacturing process while maintaining alignment accuracy.
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 approach simplifies the packaging process, reduces costs, and maintains high optical performance by achieving precise fiber alignment with controlled etching and lithography, enabling efficient light coupling and power monitoring.
Implementation Method 1
a 45-degree or 54.7-degree reflector formed in the silicon substrate
Implementation Method 2
deeply etched double U-shape trenches formed in the silicon substrate; the solution etching rates between competing crystalline planes
Data Source
AI summary
An optical system includes a silicon substrate, a 45-degree or 54.7-degree reflector formed in the silicon substrate, deeply etched double U-shape trenches formed in the silicon substrate, a thin film disposed on the reflector surface with total or partial optical refection, a top and bottom surface contacted p-i-n structure formed in the silicon substrate for optical power monitoring, a plurality of rectangular or wedge shaped spacers formed on top surface of the silicon substrate, and a surface emitting light source flip-chip bonded on the silicon substrate via the spacers.