3x3 MMI Coupler Layout for 180° Phase-Coupled Lasers
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Solution Overview
Problem
Current multimode interference (MMI) devices are not optimized for coupled lasers, lacking a 180° phase difference between output signals, which is necessary for integrating optical filters and widely tunable laser architectures.
Innovation Solution
A 3x3 multi-mode interference coupling device with specific geometric configurations and coupling coefficients is developed, enabling 180° phase difference between outer input ports, allowing for destructive interference and equal intensity output laser modes, and supporting C bar, C cen, and C x coupling coefficients, suitable for integrating optical filters and tuneable laser architectures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional MMI devices are used for coupled lasers, then the device structure is simple, but the output signals have only 90° phase difference instead of the required 180° phase difference
Solution Approach 1:
The patent changes the geometric parameters of the MMI device, specifically setting the length L = 5Lπ/2 and width W, with outer input ports displaced by W/3 from the center input port. These parameter modifications transform the phase difference from the conventional 90° to the required 180° between outer output ports, enabling the device to meet coupled laser requirements without fundamental structural changes
Solution Approach 2:
The patent introduces phase control capability through dynamic adjustment of input signals. By applying signals with 180° phase difference to outer input ports and utilizing the specific coupling coefficients (Cbar ≈ 0.78, Cen ≈ 0.57e^jπ/3), the device dynamically achieves destructive interference at the center output port and equal intensity at outer output ports, providing adaptability for different laser configurations
2Productivity
If MMI devices are optimized for switching applications, then switching performance is improved, but performance for coupled laser applications deteriorates
Solution Approach 1:
The patent designs an MMI device with universal applicability by optimizing it to work effectively for both switching applications and coupled laser applications. The device maintains the geometric structure (L = 5Lπ/2, W with W/3 displacement) that provides 180° phase difference for laser applications while preserving the multimode interference characteristics needed for switching, allowing one device to serve multiple functions
Solution Approach 2:
The patent applies different coupling coefficients to different spatial regions: Cbar (≈ 0.78) for outer-to-outer port coupling, Cen (≈ 0.57e^jπ/3) for center-to-outer port coupling, and Cx for cross-coupling. This local differentiation of coupling characteristics enables the device to optimize performance for coupled laser applications while maintaining compatibility with switching applications
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 device enables the creation of optical filters and widely tunable laser architectures with enhanced Free Spectral Range and tuning range, achieving efficient laser mode selection and stabilization with improved spectral performance.
Implementation Method 1
the C cen coupling coefficient from each outer input port destructively interferes when the propagation length L is an integer multiple of L π /2
Implementation Method 2
the output laser modes are of equal intensity when the propagation length is an integer multiple of L π /2
Data Source
Figure 1A~1D
Figure 2~3B
Figure 4~5B
AI summary
A 3x3 multi-mode interference coupling device having a length L and a width W, a center input port between a pair of outer input ports, where each outer input port is displaced from the center input port by a distance W/3, and a center output port between a pair of outer output ports, where each outer output port is displaced from the center output port by a distance W/3, where the device is supports Cbar, Ccen and a Cx coupling coefficients therein, when the outer input ports are equally excited with an input signal having a 180° phase difference, Ccen from each outer input port destructively interferes when the propagation length L is an integer number of Lπ/2, where the device outputs equal intensity laser modes from each outer output port when the propagation length is an integer multiple of Lπ/2.