Unitary Optics Array for Edge Coupling in Silicon Photonics
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Solution Overview
Problem
The integration of silicon photonics with optical fibers faces challenges due to mode spot size mismatch between PIC single-mode waveguides and commercial optical fibers, leading to high optical losses and polarization-sensitivity, especially in pluggable and separable interconnects that require economic modularity.
Innovation Solution
An optical assembly with a substrate and a unitary optics array that includes a support portion, an input surface, a redirecting surface, and an output surface, configured to receive and redirect central light rays from optical waveguides, expanding the beam to match the mode diameter of optical fibers, and using a substrate with recesses and minor surfaces to facilitate alignment and bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If direct end-fire coupling is used between waveguides and optical fibers, then alignment is simplified, but mode spot size mismatch causes high optical losses
Solution Approach 1:
An optical adapter is introduced as an intermediary component between the waveguide and optical fiber. The adapter includes a mode field adapter section that gradually transforms the mode field diameter from the waveguide size to the fiber size, enabling efficient mode field matching while maintaining alignment simplicity
Solution Approach 2:
The mode field diameter is gradually changed along the length of the optical adapter through a mode field adapter section with varying refractive index profile. This continuous parameter change enables smooth transition between different mode field sizes, reducing optical losses due to mode mismatch
2Reliability
If silicon nitride waveguides are used, then polarization sensitivity is reduced, but the mode spot size remains too small for efficient fiber coupling
Solution Approach 1:
The optical adapter serves as a mediator that accepts the small mode field from the silicon nitride waveguide and transforms it to match the larger optical fiber mode field. This intermediary structure enables efficient coupling while preserving the polarization-insensitive characteristics of the silicon nitride waveguide
Solution Approach 2:
The optical adapter employs a composite structure with a core made of silicon nitride and cladding made of silicon oxide, creating a tailored refractive index profile that enables effective mode field transformation from the waveguide to the fiber while maintaining the polarization-insensitive properties
3Adaptability or versatility
If pluggable and separable interconnects are implemented, then economic modularity is achieved, but alignment precision and coupling efficiency deteriorate
Solution Approach 1:
The optical adapter is pre-assembled and permanently bonded to the waveguide in a controlled manufacturing environment, establishing precise alignment before the pluggable connection is made. This preliminary action ensures that when the connector is plugged in, the alignment precision is already established, maintaining coupling efficiency despite the separable nature of the interconnect
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 solution provides an expanded-beam, single-mode interconnect with reduced optical losses and improved compatibility with high-bandwidth wavelength multiplexing architectures, enabling efficient and modular integration of silicon photonics with optical fibers.
Implementation Method 1
the redirecting surface is configured to receive the central light ray transmitted by the input surface along a first direction and redirect the received central light ray along a second direction different from the first direction
Implementation Method 2
expanding the beam to match the mode diameter of optical fibers
Data Source
AI summary
An optical assembly includes a substrate with a plurality of optical waveguides, and a unitary optics array assembled to the substrate. The unitary optics array includes a support portion attached to the substrate, an input surface facing a first waveguide end of each optical waveguide, a redirecting surface, and an output surface. For each optical waveguide, the input surface is configured to receive and transmit a central light ray propagating through and emitted from the first waveguide end of the optical waveguide, and the redirecting surface is configured to receive the central light ray transmitted by the input surface along a first direction and redirect the received central light ray along a second direction different from the first direction, the redirected central light ray exiting the optics array as an output central light ray through the output surface.