Tilted MMI Interferometer Phase Shift Control
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Solution Overview
Problem
Conventional interferometers with separate arms are prone to errors due to small deviations in device characteristics, leading to substantial errors in phase shift differences, which affects their proper operation, especially in designs with long arms.
Innovation Solution
An optical interferometer based on multi-mode interference (MMI) devices with a tilted propagation axis between connected MMI devices, creating a path length difference between self-imaging points to precisely control phase shift differences, eliminating the need for long arms and reducing fabrication errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional interferometers use long arms to achieve proper operation, then measurement capability is improved, but fabrication errors and device characteristic deviations cause substantial errors in phase shift differences
Solution Approach 1:
The patent changes the geometric parameter of the MMI device by introducing a tilt angle to the propagation axis. This tilt creates different path lengths for the two interfering beams within the same physical device, enabling precise phase shift control without requiring long external arms. The parameter change transforms the device from a symmetric to an asymmetric structure, resolving the contradiction between measurement precision and reliability under fabrication errors.
Solution Approach 2:
The patent introduces a new dimensional aspect by tilting the MMI propagation axis at an angle relative to the substrate plane. This creates path length differences in the vertical dimension while maintaining a compact horizontal footprint, eliminating the need for long arms and reducing sensitivity to fabrication variations in the horizontal plane.
2Measurement precision
If interferometer arms are made long to ensure proper operation, then interference pattern quality is improved, but device complexity and fabrication difficulty increase
Solution Approach 1:
The patent merges the beam splitting, path length differentiation, and beam combining functions into a single integrated MMI device structure. The tilted MMI simultaneously performs all these functions through its geometric configuration, eliminating the need for separate long arms and multiple discrete components, thus reducing device complexity while maintaining interference pattern quality.
Solution Approach 2:
By introducing the tilt angle in the vertical dimension, the patent achieves path length differentiation without extending the horizontal arm length. This dimensional change allows the interferometer to function properly within a compact footprint, reducing structural complexity and fabrication difficulty.
3Measurement precision
If separate arms are used in interferometer design, then path length difference is achieved, but sensitivity to fabrication errors and characteristic deviations increases
Solution Approach 1:
The patent merges both optical paths within a single MMI device structure, where the tilt creates different effective path lengths for the two interfering beams. This integration eliminates the sensitivity issues associated with separate arms, as any fabrication errors affect both paths equally and do not create differential phase shifts. The manufacturing precision requirement is relaxed while maintaining precise phase shift control.
Solution Approach 2:
The patent changes the geometric parameter by tilting the MMI propagation axis, creating path length differences through the tilt angle rather than through separate arm lengths. This parameter change makes the phase shift control independent of arm length fabrication variations, reducing sensitivity to manufacturing precision errors.
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 design ensures precise control over phase shift differences with minimal errors, enhancing the robustness and accuracy of interferometer operations by eliminating the reliance on long arms and common phase shifts, thus improving the reliability of interferometer devices.
Implementation Method 1
an optical interferometer based on two multi-mode interference (MMI) devices directly connected to each other, providing a precise control on a phase shift difference between different optical paths in the interferometer
Implementation Method 2
after a certain propagation distance, the modes excited at the input face are recombined in-phase such that they reproduce the optical transverse profile of the incoming light at the input face. This phenomenon is referred to as self-imaging
Data Source
AI summary
An optical interferometer based on multi-mode interference (MMI) devices includes an input port, an output port, a first MMI device connected to the input port at an input face of the first MMI device, a second MMI device connected to the first output port at an output face of the second MMI device. In the optical interferometer, an output face of the first MMI device and an input face of the second MMI device are directly connected, the first MMI device includes a first and a second self-imaging points at an interface between the first MMI device and the second MMI device, and a propagation axis of the second MMI device is tilted with respect to a propagation axis of the first MMI device, causing a path length difference between an upper optical path via the first self-imaging point and a lower optical path via the second self-imaging point.