hi pf nice to see you. I have a question about optical absorption spectrum of nanoscale substrates. To get an absorption spectrum of nanostrucutred material, I want to perform both fdtd calculation and optical simulation. When I do fdtd calculation, I set the incident light illuminated with normal incidence as I believe other researchers have same incident condition and I have a result. The result seems to make sense and is as I expected so I want to move on to the real experiment. To measure the absorption spectrum, my setup is simply to normalize the intensity of the transmitted or reflected light through or from my sample with the intensity of referenced white light. The white light goes through the objective lens and in the case of transmission spectrum the transmitted light is collected by another objective lens. My question here is: when the white light illuminated the sample how the incident angle matters? Actually I am not sure how I can say about the incident angle with white light source. I see many previous researches but it seems that they do not much care about the incident angle of white light. Thank you for time and if you have any comments please share yours.