Rib Optical Waveguide With Recessed Electrode and Dielectric Anchoring
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Solution Overview
Problem
Optical waveguide devices using LiNbO3 substrates face issues with light absorption by control electrodes and peeling of dielectric layers due to temperature changes or impacts, leading to increased optical loss and decreased electric field efficiency.
Innovation Solution
The optical waveguide device incorporates a rib-type structure with a control electrode positioned in a recessed portion of the substrate, featuring a second recessed area for a dielectric layer that strengthens light confinement and prevents peeling, using a substrate thickness of 20 μm or less and specific recess angles and dimensions to minimize optical absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control electrode is brought closer to the optical waveguide to increase electric field efficiency, then the electric field efficiency is improved, but the optical loss increases due to light absorption by the electrode
Solution Approach 1:
The patent segments the interaction space between the control electrode and optical waveguide by introducing a rib structure that divides the region into multiple zones. This segmentation allows the electric field to be concentrated in specific regions while maintaining optical confinement, thereby achieving high electric field efficiency without requiring the electrode to be in direct contact with or extremely close to the waveguide, thus avoiding excessive optical absorption.
Solution Approach 2:
The patent applies local quality by creating a rib structure with specific refractive index properties in a localized region between the electrode and waveguide. This rib structure has different optical properties than the surrounding medium, creating a localized high-index region that confines light vertically while allowing the electrode to be positioned close to the waveguide for efficient electric field interaction without causing excessive optical loss.
2Loss of energy
If a dielectric layer is used to cover the optical waveguide to prevent light scattering, then the optical loss is reduced, but the dielectric layer may peel due to temperature changes or impacts
Solution Approach 1:
The patent employs a thin film dielectric layer deposited conformally on the rib structure and waveguide surfaces. This thin film approach provides adequate optical protection and light confinement while reducing the overall thickness and mechanical stress on the dielectric layer, thereby minimizing peeling risks due to thermal expansion or mechanical impacts.
Solution Approach 2:
The patent incorporates adhesion promotion measures during the fabrication process, such as surface treatment or intermediate adhesion layers, before depositing the dielectric layer. This preliminary action ensures strong bonding between the dielectric layer and the underlying structures, preventing peeling under subsequent temperature changes or mechanical stress.
3Volume of moving object
If the substrate is thinned to achieve size reduction, then the device size is reduced, but the mechanical strength and stability may be compromised
Solution Approach 1:
The patent applies local quality by thining the substrate selectively in different regions. The substrate is thinned to 20 μm or less in the active modulation region to reduce device size and improve optical confinement, while maintaining greater thickness in peripheral regions to provide mechanical support and stability. This localized thinning approach achieves size reduction without compromising overall mechanical strength.
Solution Approach 2:
The patent employs a composite structure combining the thinned LiNbO3 substrate with supporting elements or layered configurations. This composite approach allows the active region to be thin for size reduction while incorporating stronger or thicker supporting structures that maintain mechanical integrity and stability during device operation and handling.
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
This design suppresses optical absorption by the control electrode and prevents dielectric layer peeling, enhancing electric field efficiency and reducing drive voltage while maintaining mechanical stability.
Implementation Method 1
an optical waveguide device in which LiNbO3 (hereinafter, referred to as LN) having an electro-optic effect is used in the substrate
Data Source
AI summary
An object of the present invention is to provide an optical waveguide device in which absorption of light propagating through an optical waveguide by a control electrode is suppressed and in which peeling of a dielectric layer covering the optical waveguide is prevented.An optical waveguide device of the present invention includes a substrate 1 on which an optical waveguide is formed, and a control electrode 2 disposed close to the optical waveguide on the substrate, in which the optical waveguide is a rib type optical waveguide 10, an end portion of the control electrode 2 close to the rib type optical waveguide 10 is positioned in a first recess portion C1 of the substrate that forms the rib type optical waveguide 10, a dielectric layer 3 that covers the rib type optical waveguide 10 is provided, a second recess portion C2 that is further recessed from a shallowest position of the first recess portion C1 is provided in a part of the first recess portion C1 near a base part of the rib type optical waveguide 10, and the dielectric layer 3 is disposed in at least a part of the second recess portion C2.