Three-Layer Spot-Size Conversion in Rib-Type Optical Waveguides
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Solution Overview
Problem
Existing optical waveguide elements face challenges in reducing coupling loss due to a significant mismatch in mode field diameters between the optical waveguide and optical fiber, and existing spot size converters complicate the manufacturing process and induce optical insertion loss.
Innovation Solution
An optical waveguide element with a rib-type optical waveguide and spot size conversion means comprising a first configuration layer with a tapered portion, a second configuration layer with a narrower width, and a third configuration layer covering the second layer, where the refractive indices of the layers are strategically arranged to minimize optical insertion loss and maintain a stable mode field diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a rib-type optical waveguide with narrow width is used to reduce MFD to about 1 μm, then coupling loss with optical fiber is reduced, but manufacturing precision requirements become extremely stringent
Solution Approach 1:
The optical waveguide is divided into three distinct configuration layers (first, second, and third layers) with different width characteristics. The first layer has a tapered portion for gradual expansion, the second layer has a narrowest width for precise MFD control, and the third layer provides broader support. This segmentation allows each layer to be optimized independently, reducing the overall manufacturing precision requirements while achieving the desired 1 μm MFD for low coupling loss.
Solution Approach 2:
Different regions of the optical waveguide are given different local properties through the three-layer structure. The first configuration layer has a tapered portion with gradually expanding width, the second configuration layer has the narrowest width at its center portion, and the third configuration layer has the widest width. This local quality variation enables precise control of mode field diameter in specific regions while providing tolerance in other regions, thereby reducing manufacturing precision requirements.
2Loss of energy
If spot size conversion means is added to convert MFD from 1 μm to 10 μm, then coupling loss is reduced, but optical insertion loss increases and manufacturing process becomes complicated
Solution Approach 1:
The spot size conversion function is merged with the optical waveguide structure itself through the three configuration layers, rather than being implemented as a separate component. The gradual width expansion from the first to third layers inherently performs mode field diameter conversion from 1 μm to 10 μm while the waveguide propagates light, eliminating the need for additional conversion components and simplifying the manufacturing process.
Solution Approach 2:
The patent transitions from a single-plane waveguide structure to a multi-layer three-dimensional structure. By adding the vertical dimension with three stacked configuration layers having different width profiles, the system achieves gradual mode field expansion without requiring complex lateral adjustments or additional conversion components, thereby reducing manufacturing complexity.
3Volume of moving object
If the MFD of optical waveguide is reduced to about 1 μm for miniaturization, then device size is reduced, but coupling loss with optical fiber becomes extremely large
Solution Approach 1:
The optical waveguide is segmented into three configuration layers with progressively different width characteristics. This segmentation enables the device to maintain a compact overall size while incorporating a gradual expansion region that transitions the mode field diameter from 1 μm to 10 μm, thereby reducing coupling loss without significantly increasing device volume.
Solution Approach 2:
The first configuration layer incorporates a tapered portion with gradual curvature in its width profile, creating a smooth transition zone that expands the mode field diameter progressively. This curved transition reduces abrupt discontinuities and minimizes reflection losses, enabling efficient coupling from the miniaturized 1 μm waveguide to the 10 μm optical fiber.
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 solution reduces optical insertion loss and coupling loss by allowing for less stringent positional accuracy during manufacturing, while maintaining a stable mode field diameter, thus enhancing the efficiency of optical transmission.
Implementation Method 1
an optical waveguide substrate having a rib-type optical waveguide made of a material having an electro-optic effect
Data Source
AI summary
Provided is an optical waveguide element including spot size conversion means with suppressed optical insertion loss without complicating a manufacturing process. An optical waveguide element includes an optical waveguide substrate (4) having a rib-type optical waveguide (10) formed of a material having an electro-optic effect, and spot size conversion means for changing a mode field diameter of a light wave propagating through the optical waveguide at a position where an input end or an output end of the rib-type optical waveguide (10) is formed, in which the spot size conversion means includes a first configuration layer (1) that is connected to the rib-type optical waveguide (10) and includes a tapered portion (11) in which a width of the optical waveguide expands, a second configuration layer (2) that is laminated on the first configuration layer (1) and has a width narrower than a width of the first configuration layer (1), and a third configuration layer (3) that is disposed to cover the second configuration layer (2) excluding a part of the second configuration layer (2) close to the rib-type optical waveguide and has a width wider than the width of the second configuration layer (2).