Photonic Crystal Lower Cladding for Substrate Isolation
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Solution Overview
Problem
Current photonic devices integrated on semiconductor substrates face challenges in achieving efficient optical isolation from the substrate while maintaining low signal loss and allowing for the integration of both photonic and electronic circuits on the same substrate, as traditional substrates are often unsuitable for desired operating characteristics of electronic devices.
Innovation Solution
The use of a photonic crystal structure as a lower cladding in the substrate to isolate photonic devices from the bulk substrate material, providing a low-loss light path and allowing for integration with electronic devices by forming a periodic or quasi-periodic array of elements with a refractive index lower than the waveguide core, along with additional cladding on the sides and top.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a traditional substrate is used for photonic devices, then the substrate can support both photonic and electronic circuits, but optical signal loss into the substrate increases and coupling between waveguide core and substrate modes occurs
Solution Approach 1:
A photonic crystal cladding layer is introduced as an intermediary between the waveguide core and the substrate. This cladding layer has a periodic structure with a different refractive index than both the core and substrate, creating an optical barrier that prevents direct coupling between the waveguide modes and substrate modes, thereby reducing optical signal loss while maintaining isolation.
Solution Approach 2:
The patent employs a composite structure consisting of multiple layers with different optical properties: the waveguide core material, the photonic crystal cladding layer with periodic structure, and the substrate. This composite arrangement allows the system to simultaneously achieve low optical loss, effective mode isolation, and mechanical support for both photonic and electronic devices.
2Reliability
If a silicon on insulator substrate is used for optical isolation, then coupling to substrate is prevented, but integration with electronic devices becomes difficult due to unsuitable operating characteristics
Solution Approach 1:
The photonic crystal cladding layer is applied locally only where optical isolation is needed, specifically beneath the waveguide core. The rest of the substrate maintains its original properties, allowing electronic devices to be integrated in regions where optical isolation is not required. This localized approach provides optical isolation functionality without compromising the overall substrate's suitability for electronic device integration.
3Loss of energy
If additional cladding layers are added to reduce optical loss, then signal loss decreases, but device complexity increases
Solution Approach 1:
Instead of using multiple separate cladding layers with different materials, the patent employs a single photonic crystal cladding layer with a periodic structure. The periodicity creates multiple scattering centers that work together to achieve complete optical isolation, achieving the same effect as multiple layers but with simpler fabrication and fewer material interfaces.
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 minimizes optical signal loss into the substrate, enabling efficient integration of photonic and electronic devices on the same substrate with reduced coupling between the waveguide core and substrate modes, supporting both TE and TM optical transmission modes with minimal transmission loss.
Implementation Method 1
a photonic crystal lower cladding layer provided on a semiconductor substrate. The photonic device includes a waveguide having a core optically isolated from the substrate by the photonic crystal lower cladding layer
Implementation Method 2
The coupling between the optical guide modes in the waveguide core and the silicon substrate modes is inhibited by the crystal dispersion properties of the photonic crystal
Implementation Method 3
enabling efficient integration of photonic and electronic devices on the same substrate with reduced coupling between the waveguide core and substrate modes, supporting both TE and TM optical transmission modes with minimal transmission loss
Data Source
AI summary
An integrated photonic device is provided with a photonic crystal lower cladding on a semiconductor substrate.