Two-Step Etched Grating Coupler for Lower Optical Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current grating couplers in integrated photonics face challenges in achieving high coupling efficiency and minimizing light losses, particularly in transitioning between waveguides and optical fibers, due to limitations in design and fabrication processes.
Innovation Solution
The development of a grating coupler with a two-step etching process that creates grating structures with distinct top and bottom portions of varying widths, optimized for improved diffraction efficiency, and a dielectric layer to enhance coupling efficiency and reduce light losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional single-step etching is used to fabricate grating couplers, then manufacturing process is simple, but coupling efficiency is limited and light losses are high
Solution Approach 1:
The fabrication process is segmented into two distinct etching steps: a first etching step that creates an initial grating structure, and a second etching step that modifies the grating structure to form trenches between adjacent grating elements. This segmentation allows optimization of coupling efficiency through controlled trench formation while maintaining CMOS compatibility.
Solution Approach 2:
The second etching step creates localized trenches specifically between adjacent grating elements, modifying only the regions where light coupling occurs most intensely. This local modification optimizes the refractive index contrast at critical locations without altering the overall grating periodicity or geometry, thereby reducing light losses while maintaining manufacturing feasibility.
2Loss of energy
If grating structures with uniform width are used, then fabrication is simpler, but diffraction efficiency is suboptimal
Solution Approach 1:
The grating structures are designed with asymmetric profiles resulting from the two-step etching process. The first etching creates grating elements with initial dimensions, and the second etching removes material to form trenches, creating an asymmetric cross-section that optimizes diffraction efficiency for the target wavelength while remaining compatible with standard CMOS fabrication capabilities.
3Loss of energy
If targeted wavelength coupling is optimized, then coupling efficiency at peak wavelength is high, but bandwidth is narrow
Solution Approach 1:
The grating coupler parameters including trench depth, trench width, grating element width, and grating periodicity are optimized to achieve high coupling efficiency at the targeted wavelength of 1310 nm. The two-step etching process enables precise control of these parameters to maximize diffraction efficiency at the peak wavelength while maintaining reasonable bandwidth for practical applications.
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 results in higher transmission coefficients and reduced light losses, maintaining peak efficiency at targeted wavelengths while allowing for adaptable fabrication compatible with CMOS technology and robust wavelength selection.
Implementation Method 1
grating couplers are fabricated with specific periodicity and alternation of materials to create a refractive index variation that causes incoming light of a selected frequency to be diffracted and coupled to other photonic devices
Data Source
AI summary
A device includes a dielectric layer, a plurality of grating structures, and a dielectric material between the plurality of grating structures and on top of the plurality of grating structures. The grating structures are arranged on the dielectric layer and separated from each other, the plurality of grating structures each having a bottom portion and top portion, the top portion having a first width and the bottom portion having a second width, the second width being larger than the first width.