SiGe Waveguide on Low-Index Substrate for Quantum Integration
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Solution Overview
Problem
Existing technologies face challenges in integrating silicon germanium (SiGe)/silicon (Si) optical resonators with quantum bits (qubits) and complementary metal oxide semiconductor (CMOS) devices due to optical leakage concerns, necessitating improved designs for efficient microwave-to-optical conversion on a common substrate.
Innovation Solution
A waveguide structure is developed using a silicon-on-X (SOX) configuration with a lower refractive index substrate, such as sapphire, diamond, or silicon carbide, to integrate SiGe/Si optical resonators with qubits and CMOS devices, reducing optical leakage and enhancing single photon field strength through refractive index contrast, allowing closer electrode placement and improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If SiGe on Si substrate architecture is used for optical resonators, then integration with qubits and CMOS devices is achieved, but optical leakage occurs
Solution Approach 1:
The patent employs a composite substrate structure combining SiGe layers with a lower-index substrate material (such as SiC, GaN, or sapphire). This composite architecture allows the SiGe optical resonators to benefit from both the integration advantages of silicon-based materials and the optical confinement benefits of the lower-index substrate, thereby reducing optical leakage while maintaining compatibility with qubits and CMOS devices.
Solution Approach 2:
The patent introduces a lower refractive index substrate layer specifically at the region where optical leakage occurs, creating a localized optical confinement structure. This local modification allows the rest of the device to maintain its original SiGe on Si architecture for integration, while the specific area benefits from reduced optical leakage due to the refractive index contrast provided by the lower-index substrate.
2Loss of energy
If refractive index contrast is increased to reduce optical leakage, then radiation loss is reduced, but device complexity increases
Solution Approach 1:
The patent modifies the refractive index parameter of the substrate by selecting materials with a lower index than conventional Si substrates (such as SiC, GaN, or sapphire). This parameter change creates a refractive index contrast that reduces optical leakage and radiation loss. The approach is straightforward as it involves material selection rather than complex structural modifications, thereby achieving energy reduction without proportionally increasing device complexity.
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 solution enables efficient microwave-to-optical conversion with reduced radiation loss, enabling closer integration of qubits, CMOS devices, and reconfigurable electrical routing, thereby enhancing quantum computing capabilities.
Implementation Method 1
The structured substrates have a silicon-on-X (SOX) configuration, where X is a wafer having a material with i) a lower refractive index than Si
Implementation Method 2
The ability to link microwave electrical signals and optical photons for quantum information processing requires efficient conversion between the microwave and optical domains
Data Source
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AI summary
Techniques for the integration of SiGe/Si optical resonators with qubit and CMOS devices using structured substrates are provided. In one aspect, a waveguide structure includes: a wafer; and a waveguide disposed on the wafer, the waveguide having a SiGe core surrounded by Si, wherein the wafer has a lower refractive index than the Si (e.g., sapphire, diamond, Si C, and/or Ga N). A computing device and a method for quantum computing are also provided.