Optical Modulator Ridge Structure for Coupling Loss Reduction
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Solution Overview
Problem
Optical modulators with thin substrates experience increased coupling loss between optical fibers and waveguides due to reduced substrate thickness, leading to higher insertion loss, as the light propagation mode distribution changes, causing horizontal light confinement to weaken and vertical light distribution to differ significantly from horizontal distribution.
Innovation Solution
Designing an optical modulator with a thin plate of 20 μm or less thickness, where the width of the plate at optical input or output portions is two times or less the thickness, and optionally incorporating a shape change or external members with matching refractive index to manage light distribution and reduce coupling loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the substrate thickness is reduced to achieve velocity matching and decrease driving voltage, then the coupling loss between optical fiber and optical waveguide increases
Solution Approach 1:
The patent applies local quality by creating a ridge structure at the light incident portion of the optical waveguide. This ridge structure is formed by removing part of the substrate to expose the core layer, creating a localized structural difference that confines light horizontally. The ridge portion has different geometric properties (narrower width, exposed core) compared to the bulk waveguide, enabling improved light confinement specifically at the coupling region without affecting the overall thin substrate design.
Solution Approach 2:
The patent addresses the light confinement problem by transitioning from a two-dimensional confinement approach to a three-dimensional structure. The ridge structure adds vertical dimension control by exposing the core layer at the substrate surface, creating an effective refractive index difference in the vertical direction. This dimensional change enables horizontal light confinement through the ridge geometry while maintaining the thin substrate thickness for velocity matching.
2Power
If the substrate thickness is reduced to achieve velocity matching, then the mechanical strength of the substrate decreases
Solution Approach 1:
The patent applies segmentation by dividing the substrate into two functional parts: a thin substrate region for velocity matching and a ridge structure for mechanical reinforcement and light confinement. The ridge structure is formed by selectively removing material to expose the core layer, creating a localized thicker region that provides mechanical strength at the critical light incident portion while maintaining the overall thin substrate design for electrical performance.
3Power
If the substrate thickness is reduced to 20 μm or less, then the horizontal light confinement is weakened and light distribution spreads
Solution Approach 1:
The patent applies local quality by creating a ridge structure at the light incident portion of the optical waveguide. This ridge structure is formed by removing part of the substrate to expose the core layer, creating a localized structural difference that confines light horizontally. The ridge portion has different geometric properties (narrower width, exposed core) compared to the bulk waveguide, enabling improved light confinement specifically at the coupling region without affecting the overall thin substrate design.
Solution Approach 2:
The patent addresses the light confinement problem by transitioning from a two-dimensional confinement approach to a three-dimensional structure. The ridge structure adds vertical dimension control by exposing the core layer at the substrate surface, creating an effective refractive index difference in the vertical direction. This dimensional change enables horizontal light confinement through the ridge geometry while maintaining the thin substrate thickness for velocity matching.
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 suppresses the spreading of horizontal light distribution, reducing coupling loss between the optical fiber and the modulator, while maintaining mechanical strength and simplifying fabrication, thereby improving the overall performance of the optical modulator.
Implementation Method 1
an optical modulator including a thin plate having an electrooptic effect and having a thickness of 20 μm or less
Data Source
AI summary
An optical modulator is provided. The optical modulator includes a thin plate made of an electrooptic material and having a thickness of 20 μm or less, an optical waveguide formed on a top or bottom surface of the thin plate, and a modulation electrode formed on the top surface of the thin plate to modulate light passing through the optical waveguide, wherein, in a shape of the thin plate, a width of the thin plate at an optical input portion or optical output portion of the optical waveguide is two time or less the thickness of the thin plate.