Learning Forum

[Arpan]

Hello. I am working on designing an light absorbing photonic structure which can be used for thermal energy harvesting and used in application like photo thermal therapy. Now I am trying to simulate the light matter interaction using FDTD and use the thermal generation profile in Heat module for evaluating the thermal performance of the photonic structure.

I have worked with the solar generation analysis group and used its thermal generation functionality to observe the effect heat generation in solar cell J-V characteristics. For my current application, I need similar thermal generation capability from FDTD module, but the problem lies with the nature of the source. My light source in the application is LASER, but solar generation object uses an AM 1.5 solar spectra to calculate its heat generation profile. 

I tried to use the CW generation analysis group, but that also doesn't support heat generation. Moreover, though the calculation in solar generation and CW generation object seems similar, there is a conflict in the units of source intensity for both analysis codes. 

The solar power spectrum has the units of Watts/m^2/nm while the source intensity of CW generation rate is calculated using Watts/m^2. As a result, I am facing a great problem in generating the heat profile from the FDTD. 

Any suggestion will be appriciated.

[Guilin Sun]

The analysis group can be used when the wavelength recorded by the monitor is laser, single wavelength. You can use the Advanced analysis group:

to get the absorbed power, and convert to the actual laser power in thermal simulation.

https://optics.ansys.com/hc/en-us/articles/360034915693-Calculating-absorbed-optical-power-Higher-accuracy

 

[Arpan]

Thanks a lot to Mr. Sun for the prompt reply. For my application, I need a 3D heat generation profile from FDTD which can be calculated from your suggested Power absorbed (advanced) analysis group. But to plug the heat generation profile into the Heat module using import heat feature, we need the generation file to be in a specific format as function spatial coordinates. 

How can I generate the heat generation profile in that specific format so that I can import it into the Heat module properly using the Power absorbed (advanced) analysis group?

[Arpan]

Thanks a lot to Mr. Sun for the prompt reply. For my application, I need a 3D heat generation profile from FDTD which can be calculated from your suggested Power absorbed (advanced) analysis group. But to plug the heat generation profile into the Heat module using import heat feature, we need the generation file to be in a specific format as function spatial coordinates. 

How can I generate the heat generation profile in that specific format so that I can import it into the Heat module properly using the Power absorbed (advanced) analysis group?

[Guilin Sun]

Pabs is 3D matrix. If it is single wavelength you may not need to create the 4th dimension. You can modify the analysis script.

 

[Arpan]

Thanks a lot to Mr. Sun. I have another query regarding the boundary conditions to be used during the heat profile genearion. I have noticed that the solar generation analysis object doesn't support symmetry boundary condition during heat generation. Does the abovemention process to calculate heat profile supports the symmterical boundary conditions?

[Guilin Sun]

I am not sure which tool/example you are referring to? FDTD can have symmetry BCs for sure. Please check if FDTD is controlled by script in "model" or "analysis group". If it is controlled by script, you can set the symmetry BC there.

HEAT solver by default has insulation boundary, meaning without heat exchange on the default BCs. 

Please write new post for any questions not directly related to the topic.

[Arpan]

Sorry for not making it clear. I was indeed asking about the FDTD symmetry boundary conditions. I had previouly used the heat generation profile created from the solar generation profile in the FDTD and it didn't support the symmetrical boundary condition, as seen the provided figure. My question was if I calculate the absorbed power using the advanced analysis group and use it as the heat generation profile in the lumerical device heat module (as per your suggestion in the previous reply), can I use symmetric-antisymmetric boundary conditions in the FDTD simulation (provided that my structure is symmetrical)?

[Guilin Sun]

You can use symmetry BCs in FDTD, and the result in the analysis group will automatically unfold it to normal periodic unit cell. HEAT has isulating BC that you can use on the symmetry BC.