Depressed Cladding Waveguide for Low-Loss Electro-Optical Modulation
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Solution Overview
Problem
Existing electro-optical modulators face challenges in achieving low propagation loss and low control voltage for high-speed optical switching in the GHz frequency range.
Innovation Solution
A waveguide device with a substrate of electro-optical material, featuring a waveguide with a specific arrangement of tracks that form equilateral triangles, and electrodes to provide an electro-optical modulator with reduced propagation loss and control voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a planar waveguide is manufactured in a LiNbO3 film, then the waveguide structure is simple and manufacturable, but the propagation loss exceeds 3 dB/cm which is too high
Solution Approach 1:
The patent uses a composite waveguide structure combining LiNbO3 electro-optical material with deposited dielectric layers (SiO2, Si3N4, Ta2O5) to create a depressed cladding waveguide. This composite structure reduces propagation loss to below 0.5 dB/cm while maintaining manufacturability through standard thin-film deposition techniques.
2Length of moving object
If the optical path length is increased to several centimeters, then the control voltage can be reduced to 20 V or less, but the propagation loss increases significantly
Solution Approach 1:
The patent changes the refractive index parameter by creating a depressed cladding structure where the cladding layer has a lower refractive index than the core. This parameter change enables strong optical confinement with a short interaction length (L < 1 cm), achieving both low control voltage (≤20 V) and low propagation loss (≤0.5 dB/cm) simultaneously.
3Length of moving object
If the distance between electrodes is reduced, then the control voltage decreases below 20 V, but the manufacturing precision requirements increase
Solution Approach 1:
The patent moves the electrode positioning problem from a lateral dimension to a vertical dimension by depositing dielectric layers on top of the LiNbO3 substrate. The electrode distance is controlled by thin-film deposition thickness rather than lateral lithography, reducing positioning precision requirements and enabling sub-20 V operation.
4Length of moving object
If a waveguide architecture is used to achieve short optical path and small electrode distance, then the control voltage and device dimensions are reduced, but the propagation loss must be kept below 0.5 dB/cm
Solution Approach 1:
The patent applies local quality by creating a depressed cladding region with specific refractive index properties only where needed for optical confinement. The core maintains high refractive index for strong confinement, while the cladding has reduced refractive index to minimize loss, achieving propagation loss < 0.5 dB/cm with short interaction length.
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 achieves a propagation loss below 0.5 dB/cm and a control voltage of at most 20 V, enabling fast (>1 GHz) switching operations in an electro-optical modulator.
Implementation Method 1
The forming of each track of the plurality of tracks comprises focusing a laser beam into the electro-optical material to permanently reduce a refractive index in a focus of the laser beam from the first refractive index to a second refractive index smaller than the first refractive index
Implementation Method 2
A low voltage, low insertion-loss electro-optical modulator (EOM) is a key element for high-speed optical switching
Data Source
AI summary
A waveguide device comprises a substrate comprising an electro-optical material; a waveguide formed in the electro-optical material; and a plurality of electrodes formed in a vicinity of the waveguide. The electro-optical material has a first refractive index. The waveguide comprises a plurality of tracks. The tracks comprise a second refractive index smaller than the first refractive index, are parallel to each other with a common direction defining a direction of the waveguide, and form an arrangement in a plane perpendicular to the direction of the waveguide. The arrangement comprises at least 40 equilateral triangles of identical side lengths, wherein all three corners of each of the equilateral triangles each coincide with a different track of the plurality of tracks in the plane perpendicular to the direction of the waveguide.