This page describes how to use the np Density and Temperature grid attribute objects to export electron-hole (np) density and temperature grid attribute recorded on a finite-element mesh directly from a CHARGE and HEAT simulation, and import it to FDTD or MODE.
Exporting index perturbation grid attributes from CHARGE and HEAT
np density grid attribute
To export np density data, the simulation file should contain an unstructured data set called ‘charge’ with scalar attributes ‘n’ and ‘p’. This would typically be exported from CHARGE as shown in the Mach Zehnder example. This can be done by right-clicking the charge monitor and selecting the save data with a user-specified filename.
temperature grid attribute
The temperature grid attribute data can be exported from HEAT using scripts.
Once a simulation has run, click on the 'HEAT' solver object in the object tree. This will bring up the results related to the thermal analysis. The dataset called 'thermal' is the one to be export. The script as shown below can be used to do that:
out = getresult("HEAT","thermal");
Importing index perturbation grid attributes to FDTD or MODE
The procedure for importing the np density and temperature grid attributes are the same. A sample file (rectChargeWg.mat) to test the np density grid attribute import function can be downloaded from the Mach Zehnder example.
Import using GUI
Import using script
It is also possible to import the np density and temperature grid attributes using scripts. Please refer to importdataset for further information.
Creating an index perturbation material model
The np density and temperature attributes contains information about the charge density and temperature for the specified region in the simulation. These information needs to translated into index changes by creating an index perturbation material model. Below are steps to be taken to create such material model.
1. Click 'Material' button from the main menu
2. Click 'Add' and select 'index perturbation' material model
3. Specify the material name
4. In the material properties, select the type(s) of index perturbation to be included in the material model, ie. np density and temperature. You can include only one of them or both. The index of the base material is then perturbed in accordance with options you choose for the conversion of np density / temperature to index changes.
There are three conversion options available for np Density grid attribute:
and two options for Temperature grid attribute:
For more information about models for np Density material, please visit Charge to index conversion.
Note: Parameters for the models
These parameters are material and frequency dependent, the default parameters are set for silicon at 1.55 um.
Charge to index conversion, Transferring data between electrical and optical solvers, importdataset, MZI getting started example