Advanced Simulation with Lumerical Charge - Lithium Niobate Modulators
Introduction
In this session, we will discuss the simulation of electrical systems using numerical charge. As mentioned in the previous video, we need to sweep the voltage, calculate the electric fields, and subsequently determine the Pockels effect and the Purcher index. This involves examining electric field parameters, including R33, R13, and both extraordinary and ordinary refractive indices.
Numerical Charge Simulation
The graphical user interface (GUI) of the numerical theme has been covered extensively in earlier videos. Here, we have sections for materials, geometry, simulation region, and charge. We will delve into the theme in the next video.
Material and Geometry
The setup includes:
- Quartz (Lithium Niobate) substrate
- Two ground electrodes and one signal electrode
- Lithium Niobate waveguide
- SiO2 substrate
- Background material: UV-15
The lithium niobate is XY-cut, and the signal and ground electrodes are gold. The geometry allows for viewing in different orientations: XY, YZ, and XZ views.
Material Properties
The material properties for lithium niobate include:
- Semiconductor XY-cut
- Diagonal electronic properties
- Extraordinary and ordinary permittivity
- Work function and EC value
- Mobility and insulator parameters
Different configurations can be selected from the material library.
Simulation Region
The simulation is set to 2D Y-normal with closed boundaries. The background material UV-15 has a permittivity of 3. The simulation region is defined by XSpan and ZSpan, with convergence tests recommended for optimal results.
Charge Settings
In the charge settings, we select the simulation region without coupling to multi-contour. The solver type is set to gamma, with options for multi-threading and global iteration limit. For more details, refer to the knowledge base article on our website.
The setup includes three contacts: left ground, right ground, and signal. The ground electrodes are set to zero voltage, while the signal voltage ranges from 0 to 5.5 volts.
Running the Simulation
To run the simulation:
- Select the charge and run the simulation for different voltages.
- Upon completion, view parameters such as electrostatic charge and band structure.
- Visualize the electric field distribution across the lithium niobate waveguide.
The simulation results show how the E field is distributed, with the most contribution from the EX component. The EY component is zero, and the EZ component is minimal.
Calculating the Purcher Index
Using the simulation data, we calculate the Purcher index. The process involves:
- Using electrostatic data as a variable
- Creating a matrix for the total effective index
- Calculating the perturbed index
The perturbed index changes with voltage, and these values are used in the numerical film.
Conclusion
This session covered the setup and execution of a simulation using Lumerical Charge, focusing on lithium niobate modulators. For more detailed information, please refer to our website and previous videos.
Okay, so now we will discuss the simulation of electrical simulations using numerical charge. As I discussed in my previous video, we need to sweep the voltage and then calculate the E fields. After that, we can calculate the Pockels effect and the Pochhammer index.
We need to consider the electric field parameters and R33, R13, and the extraordinary and ordinary refractive index. Let's go to the numerical charge simulation. Here, we have the GUI of the numerical theme, which I discussed in detail in my previous videos.
We have a material section and a geometry section. The simulation region is set to charge. We have a lithium niobate handle, which is our material, and a lithium niobate waveguide. The substrate is SiO 2. We can select the material and geometry to view the details.
The lithium niobate waveguide is a geometry we designed before. We can rotate the 3D structure to view it from different angles. Regarding the material, we have lithium niobate semiconductor XY-cut.
We can select the electrical, thermal properties and view the electronics property, which has diagonal permittivity for the extraordinary and ordinary index. We can select the work function and EC value for the lithium niobate. These are the parameters we can see for the lithium niobate.
Regarding the simulation region, our simulation is 2D Y normal. The boundary is closed. The background material is UV-15, which has a permittivity of 3. Regarding the charge, we will select the simulation region. Since we don't have any coupling, we will select it as a terminal.
We can set the advanced setting, such as solver type as gamma or multi-threading global iteration limit, which are important for convergence. We have a monitor for the simulation. Let's run the simulation for different voltages. The simulation is finished.
If we select the charge, we can see the electrostatic charge band structure. We can select the visualize option to view the E field. We can see how the E field is distributed through the lithium niobate waveguide. By increasing the voltage, we can see a better distribution.
We can use the parameters to calculate the Pockels index. Now, we can go to the Lumerical Charge. We need the extraordinary and ordinary refractive index, R33, and R 13. Let's run the simulation using the switch layout and run the simulation. We use electrostatic data as a variable of electro.
We can assign the pinch electrode to E. We will create a variable at the end to calculate the voltage. We change the voltage from zero to five volts and calculate the spatial index data for each step. This creates a matrix with epsilon e times ones, epsilon o, and epsilon o.
We can use this matrix to calculate the per chirp index and save the total index and per chirp index to the parameter. We can add this attribute to the plot and visualize the electrode. Let's run the simulation. We are waiting for the results.
We can see the perturbed index value change by increasing the voltage. We will use this value in the numerical simulation.
