Abdullah Al Mahmud If you're simulating then why do you need to measure the RI of the material? A robustness test will tell you how much the optical properties affect the scattering, for example. Philip Laven's MiePlot will allow you to do this.

If you really want to measure the real part of the RI then you can use immersion fluids plus Becke lines. Once you've measured the real part then you can undertake a robustness test on the imaginary. If the imaginary has a large effect (as it may do at 200 nm) then you can combine Mie and Bouguer to compare the real and calculated volume concentrations (as per ISO13320:2020). They'll agree when you have the imaginary part correct. Here's a series of webinars (registration required) that may help:

Laser Diffraction Masterclass 1: Why do you Need Material Optical Properties?

https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W200211LDBasics1.html

Laser Diffraction Masterclass 2: How Can Material Optical Properties be Calculated/Estimated

https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W200317LDBasics2.html

Laser Diffraction Masterclass 3: Optical Properties - How Can Material Optical Properties be Measured

https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W200414OpticalProp.html

Abdullah Al Mahmud This also may be useful from a webinar no longer available:

Optical properties of silica

Dear Mr. Alan,

Thank you for your generous response.

I would like to perform FDTD simulation with for the Mesoporous Silica Nanoparticles to see their optical phenomena (like reflection, absorption etc) to know if they can be implement in the Refractive index based sensors. To execute the FDTD simulation it is necessary to insert Refractive index values of materials. That is why I would like to know their values.

Any methods or equipment by which it is possible to find Refractive index values of nanoparticles would be really helpful.

Note: not for the thin film, only for the nanoparticles.

Thank you for your time.

Abdullah Al Mahmud You state: 'To execute the FDTD simulation it is necessary to insert Refractive index values of materials. That is why I would like to know their values.'

OK, this is perfect for a robustness test, if you know what this means. Use the 3S's principle - small, sensible, systematic - changes to the parameters. This will show you how changes in RI affect the end result.

Dear Mr. Alan,

Would you please suggest me some references for the "Robustness test"?

And how to implement it for the RI analysis?

Thank you for your time.

Abdullah Al Mahmud Google is your friend. You have 3 webinars to view in my first post. You will discover the answers there...