Ribbed MMI Optical Power Splitter for Temperature Stability
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Solution Overview
Problem
Multi-mode interference devices (MMI) used in silicon on insulator (SOI) optical circuits are temperature-dependent, making them unreliable in electronic circuits due to variations in dimensions, refractive index, and wavelength, which affect their operational integrity.
Innovation Solution
A modified MMI device with parallel ribs and a directional coupler is integrated to create a robust optical power splitter, where the ribs and slab dimensions are optimized to maintain power distribution and interference patterns across temperature variations, using a combination of MMI and directional coupler structures to achieve stable optical coupling and power distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the MMI device is made of silicon and embedded with electronic control circuits, then the device can be integrated into electronic circuits, but the device becomes inoperative in temperature ranges usually encountered due to temperature-dependent parameters
Solution Approach 1:
The patent introduces ribs with specific pitch dimensions into the MMI device to modify the interference pattern and create temperature-insensitive operation. By changing the structural parameters (rib pitch, rib dimensions) of the device, the operating point is shifted to a region where temperature variations have minimal impact on the interference pattern and power distribution, thus maintaining reliability across temperature ranges while preserving integration capability
Solution Approach 2:
The patent converts the harmful effect of temperature-dependent parameters into a benefit by designing the device to operate at a specific point in the interference pattern where the derivative of power distribution with respect to temperature is minimized. The temperature variations that would normally degrade performance are instead utilized to broaden the operational bandwidth by operating at a wavelength and temperature point where the system is naturally less sensitive
2Manufacturing precision
If the length of the slab is chosen to achieve a desired integer number of optical waves extraction, then the power distribution is optimized for that mode, but the device becomes sensitive to temperature variations affecting dimensions, refractive index, and wavelength
Solution Approach 1:
The patent modifies the standard MMI structure by introducing periodic ribs with specific pitch values. This changes the effective optical path and interference conditions within the device. By carefully selecting the rib pitch and dimensions, the device creates a new interference pattern that is less sensitive to temperature-induced changes in slab dimensions and refractive index, while maintaining precise power distribution to the desired number of output waves
Solution Approach 2:
The patent exploits the temperature dependence of refractive index and wavelength to broaden the operational bandwidth. By designing the ribbed structure to operate at a specific point in the interference pattern where the system naturally compensates for temperature variations, the harmful temperature sensitivity is converted into a benefit of extended operational range and reduced sensitivity to dimensional changes
Data Source
AI summary
A multi-mode interference device may include a body having an optical axis and configured to generate a stationary optical interference pattern from an incoming optical wave. The body may include ribs being parallel to the optical axis and being spaced apart to define a pitch and cause an optical coupling between the ribs.