Differential Electrode Pairs for Lithium Waveguide Modulators
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Solution Overview
Problem
Electro-optic devices face limitations in achieving low electrode and optical losses, efficient modulation at low voltages, and wide bandwidth operation due to increased electrode signal losses and higher driving voltages required at higher frequencies.
Innovation Solution
The implementation of a differential driving method using a pair of differential electrode pairs with a common positive electrode and separate grounds, where the electrodes are designed with channels and extensions to minimize microwave signal absorption and resistive losses, allowing for efficient electric field application across the waveguide with reduced voltage amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional single-ended driving is used, then device simplicity is maintained, but electrode signal losses increase and bandwidth is limited
Solution Approach 1:
The electrode system is segmented into differential pairs with separate positive and negative electrodes for each waveguide, allowing independent control and reduced signal losses through balanced differential signaling
Solution Approach 2:
Multiple waveguides share common positive and negative electrodes, merging the electrode functions to reduce total electrode count while maintaining differential signaling benefits for each waveguide
2Power
If higher driving voltages are applied, then optical modulation depth increases, but power consumption increases
Solution Approach 1:
The electrode design incorporates channels and extensions that concentrate the electric field locally at the waveguide interface, maximizing modulation efficiency at the critical interface while minimizing overall voltage requirements and power consumption
Solution Approach 2:
The electrode geometry parameters (channel width, extension length, spacing) are optimized to enhance electric field confinement and strength at the waveguide, achieving high modulation efficiency with reduced driving voltages
3Loss of energy
If electrode extensions are added to reduce losses, then microwave signal absorption decreases, but device area increases
Solution Approach 1:
Electrode extensions are added partially beyond the waveguide edges rather than fully surrounding them, providing sufficient microwave signal confinement and loss reduction while minimizing the additional area occupied by the extensions
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 approach enables low optical and electrode signal losses, allowing for effective modulation at lower voltages and wider bandwidths, reducing power consumption and device size while maintaining high modulation efficiency.
Implementation Method 1
The waveguide(s) carry an optical signal. The modulator also includes electrodes that apply an electric field to the waveguide to alter the index of refraction of the waveguide. As a result, the phase, intensity and/or polarization of the optical signal traversing the waveguide can be modulated.
Implementation Method 2
A first differential electrode pair has a first pair negative electrode and a first pair positive electrode arranged on opposing sides of the first waveguide. A second differential electrode pair has a second pair negative electrode and a second pair positive electrode arranged on opposing sides of the second waveguide.
Data Source
AI summary
An optical modulator includes optical material(s) and first and second differential electrode pairs. The optical material(s) exhibit an electro-optic effect and include lithium. The optical material(s) include first and second waveguides and first and second slab portions adjoining the first and second waveguides. The first differential electrode pair has electrodes arranged on opposing sides of the first waveguide. The second differential electrode pair has electrodes arranged on opposing sides of the second waveguide. The negative electrodes are arranged on distal sides of the waveguide relative to the other waveguide. The positive electrodes are arranged on proximal sides of waveguide relative to the other waveguide. The first and second waveguides, the first and second slab portions, and the first and second differential electrode pairs reside on a substrate structure. No portion of the first slab portion is between the first or second differential electrode pair and the substrate structure.