BTO-SiN Mode Converter with Conformal Deposition
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Solution Overview
Problem
The integration of Pockels materials like barium titanate (BTO) with silicon photonics faces challenges due to size mismatch and high chip costs, and mode converters for transferring light between dissimilar waveguides suffer from inefficient coupling and increased losses due to refractive index and geometry mismatches, requiring complex fabrication processes and precise alignment.
Innovation Solution
A mode coupler design that includes a Pockels material layer and a waveguide layer extending over the leading edge of the Pockels material layer, with a beveled or angled leading edge and a transition region formed from a subset of layers, allowing for efficient coupling between silicon nitride and BTO waveguides without planarization, using a conformal deposition process to ensure smooth optical mode transition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mode converters are used to transfer light between dissimilar waveguides, then coupling efficiency is improved, but fabrication complexity increases due to requiring multiple layers and precise alignment
Solution Approach 1:
The mode converter merges the Pockels material layer and waveguide layer into a single integrated structure. The waveguide layer is formed conformally over the Pockels material layer in one deposition step, eliminating the need for separate fabrication processes and precise alignment between multiple layers. This combining approach maintains efficient mode coupling while significantly simplifying the fabrication process.
Solution Approach 2:
The conformal deposition process provides self-alignment between the Pockels material layer and waveguide layer. The waveguide layer automatically follows the topography of the Pockels material layer, creating a self-aligned structure that eliminates the need for external alignment procedures and reduces fabrication complexity while ensuring optimal coupling efficiency.
2Reliability
If conventional mode converters with multiple layers are used, then mode matching is improved, but manufacturing precision requirements increase due to alignment tolerances
Solution Approach 1:
The conformal deposition process creates a self-aligned structure where the waveguide layer automatically conforms to the Pockels material layer topology. This self-alignment mechanism eliminates the need for high-precision external alignment procedures, reducing manufacturing precision requirements while maintaining excellent mode matching between the dissimilar waveguides.
3Reliability
If Pockels materials are integrated with silicon waveguides, then electro-optic performance is improved, but chip cost increases due to size mismatch and integration difficulty
Solution Approach 1:
The invention merges the Pockels material layer and waveguide layer into a single conformally deposited structure, simplifying the integration process. This approach maintains the excellent electro-optic performance of Pockels materials while reducing fabrication complexity and chip costs compared to traditional multi-layer bonding techniques that require precise alignment and have size mismatch issues.
Solution Approach 2:
The self-aligned conformal deposition process automatically adapts to the Pockels material layer, eliminating the need for complex alignment procedures and reducing manufacturing costs. This approach makes Pockels material integration more economically viable while preserving high electro-optic performance.
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 design enables efficient and compact mode conversion between waveguides with different refractive indices and geometries, reducing losses and simplifying the fabrication process by allowing single-step layer formation and self-aligned deposition, thereby enhancing the performance of integrated photonic circuits.
Implementation Method 1
Pockels materials avoid these problems. In such materials, a change of the refractive index is induced by an electric field.
Implementation Method 2
Core and cladding materials of a waveguide create a refractive index contrast, which results in total internal reflection, allowing the light to be confined and guided within the core.
Implementation Method 3
using a conformal deposition process to ensure smooth optical mode transition
Data Source
AI summary
A mode converter and method for fabrication that that allows efficient coupling from a standard SiN waveguide as is desirable (for edge or inter layer coupling) to a hybrid BTO/SiN waveguide (needed for efficient phase shifters).