Lumerical provides a tutorial on exactly this problem:

It contains extensive modeling instructions, descriptions of the results and also provides an example file with the simulation readily set up. 

https://kb.lumerical.com/en/particle_scattering_getting_started.html

Dear Stefan,

In the above-mentioned example, we should know the resonance peak of the nanowire(particular size). Then only we can select the source range ie, min and max. Here, min and max are set to get source intensity maximum at 345nm.

My intention is to develop a simulation that should give the resonance peak (absorption peak) and electric field intensity distribution at that particular resonance peak.

TFSF (total-field scattered-field) source and cross-section monitors helps this case. For finding resonance peak, u need to optimize the structure matching your target wavelength. 

Dear Shamjid,

Follow the instruction below to simulate the extinction, scattering and absorption cross-sections

1. Define your geometry.

2. Add material property from the database available under Lumerical or click here to get more materials.

https://refractiveindex.info/

3. Define your simulation region and add other parameters just mentioned in the link below and then simulate.

https://support.lumerical.com/hc/en-us/articles/360042703433-Mie-scattering-FDTD-

4. To plot all the cross-section spectrum you need to create .lsf script file that will read the output data from .fsp file and plot it into a separate window.

Hope it helps !!!

Dear Shamjid Palappra , Stefan Fossati ,

Did you found how to calculate it?

Hi Dears, I have the same question with "Shamjid Palappra" how can I calculate the extinction, scattering and absorption cross section of Metallic Nano particles embedded in active layers of organic solar cells using Lumbrical FDTD solver on ANS.?