Differential Drive Binary Weighted Optical Modulator
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Solution Overview
Problem
Existing optical modulators face challenges in achieving low electrode and optical losses, high frequency operation, and sufficient optical modulation at lower driving voltages, which limits their performance and applicability.
Innovation Solution
The optical modulator incorporates a driving module with differential inputs and outputs, coupled with differential electrodes and waveguides made of thin film lithium-containing electro-optic materials. This configuration allows for efficient modulation of optical signals with low loss transmission and high bandwidth, using binary weighted signals and a digital signal processor for feedback and signal trimming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical modulators are designed to provide sufficient optical modulation, then modulation performance is improved, but electrode driving voltages increase and losses increase
Solution Approach 1:
The modulator is divided into multiple parallel waveguide paths (first waveguide and second waveguide) with separate electrodes applied to each path. This segmentation allows independent optimization of each path and enables differential signaling that reduces common-mode noise and improves modulation efficiency while maintaining low losses.
Solution Approach 2:
The patent changes the electro-optic material parameter by using thin film lithium niobate (TFLN) with specific thickness (e.g., 180 nm) and applies differential voltage signals across the electrodes. This parameter optimization enables sufficient modulation depth at lower driving voltages while minimizing electrode and optical losses through precise control of the electro-optic interaction.
2Speed
If optical modulators operate at high frequencies, then bandwidth is improved, but electrode losses and optical losses increase
Solution Approach 1:
By segmenting the modulator into parallel waveguide paths with dedicated electrodes, the patent reduces the electrode length and surface area required for high-frequency operation. This segmentation enables high-frequency operation up to 300 GHz while minimizing resistive heating and ohmic losses in the electrodes, as well as reducing optical losses through optimized waveguide geometry.
Solution Approach 2:
The patent optimizes the electro-optic material thickness and electrode spacing parameters to minimize parasitic capacitance and inductance at high frequencies. This parameter tuning enables the modulator to operate at bandwidths up to 300 GHz while maintaining low electrode and optical losses through reduced skin effect and optimized light-electrode interaction.
3Power
If optical modulators provide large modulation at low voltages, then modulation efficiency is improved, but device complexity increases
Solution Approach 1:
The modulator uses two parallel waveguide paths with separate electrodes, creating a differential modulation structure. This segmentation enables large modulation depth at low voltages by applying complementary differential signals that cancel common-mode noise and reduce voltage requirements, while the modular structure maintains manageable device complexity through standardized waveguide and electrode designs.
Solution Approach 2:
The patent optimizes the electro-optic material properties (thin film lithium niobate with specific thickness) and electrode geometry parameters to achieve high modulation efficiency at low voltages. This parameter optimization enables the device to provide large modulation depths with minimal driving voltages while maintaining a relatively simple device structure that can be fabricated using standard semiconductor manufacturing processes.
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 enables the optical modulator to operate with low electrode and optical losses, achieve high bandwidth up to 300 GHz, and provide sufficient optical modulation at lower driving voltages, thereby improving its performance and versatility.
Implementation Method 1
one or more waveguides formed using materials having an index of refraction that is sensitive to electric fields... 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.
Data Source
AI summary
An optical modulator including a driving module, waveguide(s), and differential electrodes is described. The driving module has a first number of differential inputs and a second number of differential outputs. The second number is equal to the first number multiplied by an even integer. The waveguide(s) include a thin film lithium-containing (TFLC) electro-optic material. Each of the waveguide(s) has multiple arms. The differential electrodes are coupled to the second number of differential outputs, each of the plurality of differential electrodes including a positive electrode and a negative electrode, at least a portion of an arm of the plurality of arms between a portion of the positive electrode and a portion of the negative electrode.