Planar Lightwave Circuit Alignment Using Dummy Waveguide Mirrors
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Solution Overview
Problem
Existing methods for aligning optical axes in planar lightwave circuits are costly and increase circuit footprint, as they require etching or additional aligning waveguides, making precise and stable optical connections challenging, especially when dealing with small cores or non-visible light elements.
Innovation Solution
A planar lightwave circuit design featuring mirror structures on second input/output waveguides at the substrate end face, allowing precise alignment without additional fabrication steps or footprint increase, using Bragg gratings or grooves, and differing in width, number, or reflectance to distinguish between waveguides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If etching opposite sides of the core is performed to facilitate core location, then ease of operation is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent introduces an aligning waveguide as an intermediary structure that facilitates optical axis alignment without requiring etching of the core. The aligning waveguide serves as a mediator between the monitoring system and the core, enabling precise alignment through its larger, more easily monitorable core structure while keeping the actual signal-carrying core intact and unmodified.
Solution Approach 2:
The patent separates the alignment function from the signal transmission function by introducing a distinct aligning waveguide structure. This segmentation allows the alignment task to be performed by a specialized structure with larger dimensions optimized for monitoring, while the original core remains unchanged for its primary signal transmission purpose.
2Ease of operation
If an aligning waveguide is additionally provided to connect planar lightwave circuits, then ease of operation is improved, but area of stationary object increases
Solution Approach 1:
The patent merges the aligning waveguide and the signal transmission waveguide into a single integrated structure. The aligning waveguide and core are formed in the same fabrication process and share the same physical space, eliminating the need for separate alignment structures and reducing the overall circuit footprint.
Solution Approach 2:
The waveguide structure is designed to serve multiple functions simultaneously: it acts as both an aligning waveguide for optical axis alignment and as a signal transmission waveguide for carrying optical signals. This multi-functionality eliminates the need for separate structures and reduces the overall area required.
3Measurement precision
If active packaging method with high-powered camera monitoring is used, then measurement precision is improved, but loss of time increases due to multiple alignment steps
Solution Approach 1:
The patent incorporates the aligning waveguide structure into the initial fabrication process, performing the alignment function preparation in advance. The aligning waveguide is formed during the standard fabrication process, so no additional alignment steps or time-consuming adjustments are needed during assembly - the alignment capability is built-in from the start.
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
Enables cost-effective, precise, and stable optical connections by determining mirror structure positions using reflected laser light, distinguishing between waveguides, and avoiding additional fabrication steps or aligning waveguides, thus reducing connection costs and footprint.
Implementation Method 1
the mirror structure is arranged in a region spaced apart from an input/output end of the first input/output waveguide so that light propagating through a core of the first input/output waveguide is not coupled to the mirror structure
Data Source
AI summary
To provide a planar lightwave circuit capable of being optically connected to a semiconductor optical element or an optical wiring component in a simple, precise, and stable manner without an increase in circuit footprint or the number of fabrication steps or a deterioration of characteristics. By arranging a dummy optical waveguide having a mirror function in the vicinity of an input/output waveguide of an optical functional circuit forming the planar lightwave circuit, a semiconductor optical element or an optical wiring component can be easily aligned with and fixed to the optical functional circuit by monitoring the reflection light intensity from the dummy optical waveguide. When the optical functional circuit has a plurality of input/output waveguides to be optically connected, each input/output waveguide can be identified if the dummy optical waveguides having the mirror function have different reflection properties (such as reflectance, width, position, or reflection wavelength).