SiPh-PLC Optical Transceiver Coupling via Bragg Grating and Turning Mirror
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Solution Overview
Problem
Existing optical transceivers face challenges in achieving high-speed detection and modulation, multiplexing, and demultiplexing with efficient coupling between silicon photonics (SiPh) and planar lightwave circuit (PLC) chips, due to low tolerance for misalignment and limitations in coupling techniques such as edge coupling and grating coupling.
Innovation Solution
An integrated optical device combining a PLC chip with a SiPh chip, featuring a Bragg grating that diffracts light onto a turning mirror to focus it onto the PLC waveguide, along with a mode field converter to adapt light modes, enhancing coupling efficiency and supporting multiple transverse modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If SiPh chips use smaller modes and smaller footprint, then high speed detection and modulation is achieved, but tolerance of misalignment to fibers/lasers decreases
Solution Approach 1:
A mode field converter is introduced as an intermediary component between the SiPh waveguide and PLC waveguide. This converter adapts the mode field shape from the small-footprint SiPh waveguide to match the larger PLC waveguide mode, enabling efficient coupling while maintaining the high-speed benefits of SiPh technology without requiring extremely tight alignment tolerances
Solution Approach 2:
The mode field converter transforms the optical mode parameters (field distribution, size, shape) to bridge the gap between the small SiPh waveguide mode and the larger PLC waveguide mode. By changing the mode field parameters gradually through the converter structure, coupling efficiency is improved while alignment tolerance is relaxed
2Speed
If SiPh chips are used for high speed detection and modulation, then detection and modulation performance is improved, but capability for passive multiplexing and demultiplexing is lost
Solution Approach 1:
The optical transceiver system is segmented into two specialized chips: a SiPh chip for high-speed detection and modulation functions, and a PLC chip for passive multiplexing and demultiplexing functions. By dividing the system into functional segments, each chip can be optimized for its specific purpose while working together as an integrated system
Solution Approach 2:
The SiPh chip and PLC chip are merged into a hybrid integrated optical device where the SiPh waveguide couples to the PLC waveguide via a mode field converter. This combination allows the system to simultaneously achieve high-speed detection/modulation from the SiPh chip and passive multiplexing/demultiplexing from the PLC chip
3Ease of manufacture
If PLC chips are used for coupling to fibers and lasers with multiplexing capability, then coupling efficiency and multiplexing are improved, but high speed detection and modulation capability is reduced
Solution Approach 1:
The system segments functions between two chip types: PLC chip for coupling and multiplexing, SiPh chip for high-speed detection and modulation. This segmentation allows each component to excel at its designated function without compromise
4Loss of energy
If Bragg grating is designed to focus light within one Rayleigh distance, then coupling efficiency between SiPh and PLC chips is improved, but device complexity increases
Solution Approach 1:
The Bragg grating is designed with specific parameters (grating period, length, depth) to focus light within one Rayleigh distance of the PLC waveguide end facet. By optimizing these parameters, the grating achieves efficient coupling while maintaining a relatively simple planar structure that can be fabricated using standard processes
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 hybrid approach improves coupling efficiency, enables efficient multiplexing and demultiplexing, and supports multiple modes, leading to better detection of weak signals and increased tolerance to misalignment, thereby optimizing the performance of optical transceivers.
Implementation Method 1
The SiPh chip has a SiPh waveguide which includes a Bragg grating which diffracts light from the SiPh waveguide toward the PLC chip
Implementation Method 2
The PLC chip also has a turning mirror to reflect light emitted from the Bragg grating onto the end facet of the PLC waveguide
Data Source
AI summary
Roughly described, an integrated optical device includes both a PLC chip and an attached SiPh chip. The PLC chip has a PLC waveguide which terminates at an end facet. The SiPh chip has a SiPh waveguide which includes a Bragg grating which diffracts light from the SiPh waveguide toward the PLC chip. The PLC chip also has a turning mirror to reflect light emitted from the Bragg grating onto the end facet of the PLC waveguide. The Bragg grating is designed to direct light emitted from the Bragg grating into the end facet of the PLC waveguide so that after reflecting off the turning mirror the light focuses within one Rayleigh distance of the end facet of the PLC chip.