Engineered Lithium Niobate Substrate for SiPh Integration
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Solution Overview
Problem
The integration of electro-optic devices using lithium-containing thin film electro-optic (TFEO) materials with silicon photonics (SiPh) devices is hindered by the mismatch between the thick buried oxide (BOX) layers in TFEO devices and the thinner BOX layers in SiPh devices, leading to adverse effects on the performance of TFEO components.
Innovation Solution
The implementation of a substrate with a trench region that has an effective microwave index tailored by the combination of substrate material and trench fill, allowing for the reduction of the BOX layer thickness while maintaining effective microwave mode confinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick BOX layer is used in TFEO devices, then microwave mode confinement is improved, but integration with SiPh devices becomes difficult
Solution Approach 1:
The substrate is engineered with spatially varying properties: a first region with a first microwave index of refraction and a second region with a second microwave index of refraction. This local differentiation allows the substrate to provide both strong microwave mode confinement (in the first region) and compatibility with SiPh devices (in the second region), resolving the contradiction between reliability and adaptability.
Solution Approach 2:
The substrate functions as a composite structure with distinct regions having different microwave indices of refraction. This composite approach enables the substrate to simultaneously exhibit properties needed for TFEO device performance (thick BOX-like confinement) and SiPh device integration (thinner BOX-like compatibility), effectively combining the benefits of both thick and thin BOX layer configurations.
2Adaptability or versatility
If a thin BOX layer is used to enable SiPh integration, then adaptability is improved, but velocity matching between optical and microwave signals deteriorates
Solution Approach 1:
The substrate provides different local environments for microwave propagation: one region optimized for confinement (higher index) and another region optimized for velocity matching (lower index). This spatial differentiation allows the system to achieve both SiPh integration compatibility and proper velocity matching between optical and microwave signals without requiring a uniformly thick BOX layer.
Solution Approach 2:
The microwave index of refraction is varied across different regions of the substrate. By changing this parameter locally, the substrate can provide both the strong confinement needed for TFEO operation and the appropriate propagation velocity for matched signal timing, resolving the contradiction between adaptability and speed 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 approach improves the velocity matching between optical and microwave signals, enhancing the performance of integrated electro-optic devices by reducing velocity mismatch between optical modes in waveguides and microwave modes in electrodes.
Implementation Method 1
The BOX layer is between the lithium-containing TFEO component (e.g. waveguide) and an underlying silicon substrate. These BOX layers are generally at least five micrometers to ten micrometers thick. The thick BOX layers allow the microwave mode for microwave signals carried by the electrodes to be within the BOX layer and not extend to the underlying silicon substrate.
Implementation Method 2
This approach improves the velocity matching between optical and microwave signals, enhancing the performance of integrated electro-optic devices by reducing velocity mismatch between optical modes in waveguides and microwave modes in electrodes.
Data Source
AI summary
An electro-optic device is described. The electro-optic device includes a substrate, an insulator on the substrate, an optical structure on the insulator and an electrode proximate to at least a portion of the optical structure. The substrate includes a trench region having a plurality of trenches therein. The trench region has an effective microwave index based on a substrate material and the plurality of trenches. The insulator is on the substrate. The optical structure is on the insulator. The optical structure has a thin film electro-optic layer including lithium. The electrode is proximate to a portion of the optical structure.