Optical Waveguide Electrode Crossings With Curved Resin Buffer
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Solution Overview
Problem
Optical absorption losses and reduced long-term reliability due to stress-induced damage at intersections of optical waveguides and electrodes in optical modulators, particularly in convex optical waveguides on thin LN substrates, which affect extinction ratio and overall device performance.
Innovation Solution
Incorporating a resin layer between optical waveguides and electrodes with a curved boundary at intersections, and optionally an intermediate SiO2 layer, to reduce stress and absorption losses while maintaining optical and electrical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If electrodes are formed to extend to the vicinity of the outer periphery of the LN substrate for connection with external electric circuits, then electrical connection is achieved, but optical absorption loss increases due to metal contact at intersections with optical waveguides
Solution Approach 1:
A buffer layer made of SiO2 is introduced as an intermediary substance between the electrode metal and the optical waveguide at intersection points. This buffer layer prevents direct contact between the metal electrode and the optical waveguide core, thereby eliminating optical absorption loss while maintaining electrical connection functionality. The SiO2 layer serves as a mediator that allows the electrode to extend to the substrate periphery for external connection without causing harmful optical-metals interaction.
2Loss of energy
If a buffer layer made of SiO2 is provided on the substrate surface and electrode metal is formed above the buffer layer to reduce optical absorption loss, then optical loss is reduced, but stress is applied to the substrate due to higher rigidity of SiO2 compared to LN substrate
Solution Approach 1:
Instead of forming a continuous SiO2 buffer layer across the entire substrate surface, the invention applies the SiO2 buffer layer locally only at the intersection points where electrodes cross over optical waveguides. This localized application reduces the overall stress on the LN substrate while still providing optical loss protection at the critical intersection regions. The buffer layer is formed with controlled thickness and spatial distribution to balance optical performance and mechanical stress considerations.
3Adaptability or versatility
If the number of intersections between optical waveguides and electrodes increases due to miniaturization, multi-channelization, or high integration, then device functionality is enhanced, but optical absorption loss becomes a non-negligible factor limiting device performance
Solution Approach 1:
The SiO2 buffer layer is systematically applied at all intersection points between electrodes and optical waveguides throughout the integrated device structure. This intermediary layer provides a universal solution that scales with device complexity, allowing miniaturization, multi-channelization, and high integration without proportionally increasing optical absorption losses. The buffer layer strategy enables dense routing of electrodes and waveguides while maintaining optical performance.
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
Effectively reduces optical absorption losses and prevents stress-induced damage, enhancing the long-term reliability and performance of optical waveguide devices without deteriorating optical characteristics.
Implementation Method 1
a resin layer is provided between the optical waveguide and the electrode at the intersection... prevents stress-induced damage
Implementation Method 2
LiNbO3 (hereinafter, also referred to as LN) having an electro-optic effect... to further strengthen the interaction between the signal electric field and the guided light
Data Source
AI summary
In an optical waveguide device using a convex optical waveguide, the absorption loss of guided light at an intersection between an optical waveguide and an electrode is reduced, without deteriorating optical characteristics and reducing long-term reliability. Provided is an optical waveguide device including a substrate on which an optical waveguide is formed, and an electrode having an intersection crossing over the optical waveguide on the substrate, in which the optical waveguide is formed with a protruding portion extending on the substrate, a resin layer is provided between the optical waveguide and the electrode at the intersection, the resin layer is formed to cover an upper surface and a side surface of the protruding portion of the optical waveguide, and in a cross section along a width direction of the optical waveguide, a boundary with the electrode is formed with a curve.