Negative Angle Grating Coupler for Passive Alignment
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Solution Overview
Problem
Coupling light from single mode edge emitting lasers to silicon photonics is costly and requires tight alignment tolerances, typically less than 0.5 micrometers, necessitating active alignment and multiple components like lenses and isolators.
Innovation Solution
The implementation of a negative angle grating coupler system that eliminates the need for lenses by using a grating coupled laser and photonic integrated circuit with transmit and receive grating couplers, allowing for passive alignment and reduced component count, featuring a silicon nitride or silicon grating coupler with specific tooth heights and duty cycles to enhance coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional lens-based coupling is used, then alignment precision can be achieved, but device complexity and cost increase
Solution Approach 1:
The patent removes the lens component from the traditional coupling system, extracting only the essential grating coupler functionality. This eliminates the need for complex lens alignment while maintaining coupling precision through the grating structure's inherent optical properties
Solution Approach 2:
The grating coupler structure provides self-alignment capabilities through its periodic pattern, which naturally guides light coupling without requiring external lens elements. The structure serves its own alignment function through the diffraction grating effect
2Reliability
If traditional lens-based coupling is used, then light coupling can be achieved, but quantity of components increases
Solution Approach 1:
The patent merges the coupling function directly into the waveguide structure through integrated grating couplers, combining what were previously separate components (lens, isolator, coupler) into a unified photonic integrated circuit structure
Solution Approach 2:
The grating coupler structure performs multiple functions simultaneously: it couples light, provides isolation through the negative angle design, and integrates directly with the waveguide, eliminating the need for separate dedicated components for each function
3Measurement precision
If tight alignment tolerances are required, then coupling precision is maintained, but ease of operation decreases
Solution Approach 1:
The patent changes the grating angle parameter to a negative value, which fundamentally alters the coupling characteristics to provide broader tolerance windows. This parameter change transforms the system from requiring sub-micrometer precision to allowing larger alignment variations while maintaining effective coupling
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 solution reduces coupling loss by half compared to previous embodiments, increases alignment tolerances by a factor of 10 or more, and enables wafer level testing, simplifying packaging and reducing system size and cost.
Implementation Method 1
a receive grating coupler optically coupled to the second waveguide... incident light on the receive grating coupler that has a lateral component parallel to the waveguide is coupled into the waveguide
Data Source
AI summary
In an example, a system includes a grating coupled laser and a photonic integrated circuit. The grating coupled laser includes a first waveguide and a transmit grating coupler optically coupled to the first waveguide. The photonic integrated circuit includes a second waveguide and a receive grating coupler optically coupled to the second waveguide. The second grating coupler may include a negative angle grating coupler.