Optical Multiplexer Asymmetric Waveguide Dummy Structure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Optical multiplexers for image projection devices face challenges in maintaining waveguide asymmetry during heat treatment, leading to inward waveguide fall and failure in light coupling due to incomplete low refractive index silicon oxide filling, which conventional dummy waveguides cannot fully address, especially in densely packed and asymmetric designs.
Innovation Solution
Incorporating a horizontally flipped dummy waveguide asymmetrically positioned with respect to the center line of directional couplers or Mach-Zehnder interferometers, formed from the same material as the waveguides, to prevent inward waveguide fall by adjusting its distance to balance fall prevention and light coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dummy waveguides are provided symmetrically on the outer sides of the light coupling section, then waveguide fall inward is prevented, but asymmetric waveguide fall cannot be fully addressed leading to light coupling failure
Solution Approach 1:
The patent applies asymmetry by providing dummy waveguides only on the outer side of the light coupling section where the waveguide is located asymmetrically with respect to the center line. This asymmetric dummy waveguide configuration matches the asymmetric waveguide layout, effectively preventing inward fall of asymmetric waveguides while avoiding unnecessary structures on the symmetric side.
Solution Approach 2:
The patent applies local quality by providing dummy waveguides only in specific locations where asymmetric waveguides are positioned, rather than uniformly on both sides. The dummy waveguide is provided locally on the outer side of the light coupling section where needed, making the structure more adaptable to asymmetric configurations while maintaining effectiveness in preventing waveguide fall.
2Reliability
If the distance of dummy waveguide from center line is set for symmetry, then fall prevention is optimized, but light coupling efficiency may be compromised
Solution Approach 1:
The patent applies parameter changes by optimizing the distance of the dummy waveguide from the center line of the directional coupler. The distance is set to satisfy the inequality 0.5W ≤ d ≤ 2W, where W is the width of the light coupling section. This parameter optimization balances the fall prevention effect with minimal impact on light coupling efficiency, allowing the dummy waveguide to be effective without excessively reducing the light coupling area.
3Volume of moving object
If directional couplers are placed close to each other for compact design, then device size is reduced, but waveguide fall risk increases due to incomplete oxide filling
Solution Approach 1:
The patent applies the intermediary principle by introducing dummy waveguides as mediator structures between the asymmetric waveguides and the surrounding environment. These dummy waveguides act as placeholders that induce proper oxide filling in the light coupling sections, thereby preventing waveguide fall without requiring increased spacing between directional couplers, thus maintaining compact device size while improving structural stability.
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 effectively prevents inward waveguide fall and ensures proper light coupling, improving product yield and reducing production costs by optimizing the placement and distance of dummy waveguides relative to the center line, thereby enhancing the multiplexing properties of optical multiplexers.
Implementation Method 1
forming a low refractive index silicon oxide layer and a high refractive index silicon oxide layer on a silicon substrate by a known method such as chemical vapor deposition (CVD)
Implementation Method 2
In such cases, these two waveguides in the light coupling section fall inward symmetrically in a heat treatment step, which follows the aforementioned step of over-cladding the low refractive index silicon oxide layer
Data Source
AI summary
The present invention provides an optical multiplexer that includes waveguides forming an asymmetric shape with respect to the light traveling direction and can work as designed even when it is obtained through a heat treatment.The optical multiplexer includes at least three input optical waveguides, at least two directional couplers, and at least one output optical waveguide such that the waveguides including the input optical waveguides form an asymmetric shape with respect to a light traveling direction. The optical multiplexer further includes at least one dummy waveguide that is in a horizontally flipped shape of a waveguide located asymmetrically with respect to a center line of the directional couplers or a Mach-Zehnder interferometer composed of a combination of two of the directional couplers. Thus, a waveguide in a light coupling section of each of the directional couplers is prevented from falling inward.