Dual-Layer Grating Coupler for Reduced Directionality Losses
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Solution Overview
Problem
Conventional grating couplers in optical communications face significant directionality losses due to the difficulty in optimizing light coupling between photonic integrated circuits and external optical components, particularly when using single etch steps, which restricts the choice of waveguide layer thickness and etch depth, and 2D gratings face challenges in loss optimization due to conflicting requirements from multiple light beams.
Innovation Solution
A dual-layer grating coupler design with offset scatterers in stacked gratings, where each grating layer has a two-dimensional arrangement of scatterers, allowing optical signals to be redirected with reduced directionality losses by decoupling the design from the buried oxide layer thickness, thereby improving coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single etch step is used to fabricate gratings, then the manufacturing process is simplified, but directionality losses increase due to restricted choices in waveguide layer thickness and etch depth
Solution Approach 1:
The grating structure is divided into two separate etch steps creating distinct gratings in different layers. The first grating is formed in the waveguide layer with a first etch depth, and the second grating is formed in the buried oxide layer with a second etch depth. This segmentation allows independent optimization of each grating's parameters to minimize directionality losses while maintaining fabrication simplicity.
2Adaptability or versatility
If 2D gratings are used to allow multiple beams to propagate simultaneously, then functionality is enhanced, but loss optimization becomes limited due to conflicting requirements from multiple light beams
Solution Approach 1:
The solution moves from optimizing a single 2D grating plane to a three-dimensional stacked grating structure. By adding the vertical dimension with two gratings at different depths, the system can handle multiple light beams propagating in different directions simultaneously. Each grating can be optimized for specific beam directions, reducing conflicting requirements and minimizing overall coupling losses.
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 dual-layer grating coupler reduces directionality losses from 1.3 dB to 0.3 dB or 0.6 dB to 0.2 dB, enhancing the coupling efficiency and allowing for greater flexibility in choosing the buried oxide layer thickness to improve the performance of other devices.
Implementation Method 1
Grating couplers facilitate the coupling of light between photonic integrated circuits and external optical components... Gratings may be fabricated by etching a planar waveguiding material... 2D diffractive patterns may be needed
Data Source
AI summary
According to an embodiment, an apparatus includes a first grating and a second grating in a stack with the first grating. The first grating includes a first plurality of scatterers in a first two-dimensional (2D) arrangement. The second grating includes a second plurality of scatterers in a second 2D arrangement. The first grating and the second grating are arranged to redirect a first optical signal and a second optical signal traveling through the stack. The first optical signal enters the stack in a first direction, and the second optical signal enters the stack in a second direction different from the first direction. Each of the second plurality of scatterers is offset from a corresponding scatterer of the first plurality of scatterers in a third direction different from the first and second directions. Other embodiments include a method performed by the apparatus.