Multimode Interference Coupler Layout for Compact Optical Routing
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Solution Overview
Problem
Existing optical devices with multimode interference lenses face challenges in downsizing due to large crossing angles between waveguides, which can increase device size and complexity.
Innovation Solution
The use of a coupler with a multimode interference waveguide that reduces the interval between ports and employs a high mesa structure, allowing for a smaller device footprint and easier manufacturing, while maintaining efficient light guidance and reducing wavelength dependence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the crossing angle of two waveguides is set between 80° and 100° to ensure transmission quality, then light transmission quality is improved, but the device size increases making downsizing difficult
Solution Approach 1:
The patent transitions from a planar two-dimensional waveguide layout to a three-dimensional stacked configuration. Multiple waveguides are arranged in different layers (first waveguide layer and second waveguide layer) with vertical separation, allowing waveguides to intersect without requiring large horizontal crossing angles. This dimensional change enables compact device footprint while maintaining proper light coupling and transmission quality.
Solution Approach 2:
The optical device is segmented into multiple functional layers: first waveguide layer, second waveguide layer, and coupling regions. Each layer handles specific waveguide routing functions, with the first layer containing first and second waveguides and the second layer containing third and fourth waveguides. This segmentation allows independent optimization of each layer's geometry and reduces interference between waveguides.
2Area of stationary object
If waveguides are arranged with small intervals to reduce device size, then device footprint is reduced, but manufacturing precision requirements increase
Solution Approach 1:
By utilizing the vertical dimension with stacked waveguide layers, the patent achieves compact horizontal spacing without compromising manufacturing feasibility. The vertical separation between layers provides manufacturing tolerance buffer, reducing the stringency of lateral alignment requirements while maintaining small overall device footprint.
Solution Approach 2:
The patent introduces coupling regions as intermediary structures between waveguides in different layers. These coupling regions facilitate optical energy transfer between layers through controlled evanescent field coupling or direct end-face coupling, enabling flexible waveguide routing with relaxed alignment tolerances compared to direct waveguide-to-waveguide coupling.
3Ease of operation
If a multimode interference lens is used at waveguide intersections, then light guidance is achieved, but device complexity and size increase
Solution Approach 1:
The patent extracts the light guidance function from complex multimode interference lenses and implements it through simpler waveguide end-face coupling or evanescent field coupling mechanisms. The coupling regions use basic optical principles rather than complex interference effects, reducing device complexity while maintaining effective light guidance between intersecting waveguides.
Solution Approach 2:
The patent uses standardized waveguide coupling structures that can be replicated across multiple intersection points. Rather than requiring unique complex interference lenses at each intersection, the same simple coupling region design is copied and applied throughout the device, reducing overall complexity and enabling scalable manufacturing.
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 configuration enables a compact optical device with improved light transmission quality, easier port connectivity, and reduced manufacturing complexity, while minimizing signal loss and phase differences between I and Q signals.
Implementation Method 1
a multimode interference waveguide configured to guide light input from the first port to the third port and guide light input from the second port to the fourth port
Data Source
AI summary
An optical device includes: a coupler that includes a first port, a second port, a third port, a fourth port, and a multimode interference waveguide; a first waveguide that is optically connected to the first port, the first waveguide being configured to guide light that is input to the coupler via the first port; a second waveguide that is optically connected to the second port, the second waveguide being configured to guide light that is input to the coupler via the second port; a third waveguide that is optically connected to the third port, the third waveguide being configured to guide light that is output from the coupler via the third port; and a fourth waveguide that is optically connected to the fourth port and, the fourth waveguide being configured to guide light output from the coupler via the fourth port.