Compare absorption spectra from calculation and experiment

[lhk]

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.

 

[gtoguy97]

Thank you for your question! The incident angle of white light does matter when taking an absorption spectrum. In general, the incident angle of the white light should be kept as close to normal as possible in order to maximize the accuracy of the measurement. If the angle is too large, this can lead to refraction effects which can affect the accuracy of the measurements. Additionally, the objective lenses used for collecting the transmitted light should also be adjusted to account for the incident angle of the white light. It is important to note that the incident angle of the white light may need to be adjusted depending on the sample size and geometry.