The refractive index of an alloy is RMS value of individual elements refractive index.

means, na = sqrt (n1 square  + n2 square + n3 square + .......)

The text by James R. Craig and David J. Vaughan, 2nd edition, 1994 Ore Microscopy & Ore Petrography, Chapters 4 and 5 may be of some help.

Hi Priyank, one option for getting refractive index of alloy is from Spectroscopic Ellipsometer. This technique is totally model-based. So, if you can fit your data then you can get correct value of refractive index of your system.

Dear Priyanka Mohan,

By performing UV-Vis-NIR you can get the refractive index.

If you have transmittance data, first you need to calculate the absorption

coefficient (alpha-a)

alpha = 2.303 log (1/T)/t where t-thickness of the sample

then, reflectance(R) in terms of absorption

coefficient (alpha-a)

R = (exp(−at)+(or)-((exp(−at)T -exp(-3at)T+exp(-2at)T2)1/2)/exp(−at)+exp(-2at)T

then

n = (-(R + 1)+(or)- 2R1/2)/R-1

where n is refractive index

I hope this information may help you.

Dear Priyank,

Using the Sellmeier equation( n) refractive index can be calculated.

N= √A+B/1-[C. Eg alloy fraction components/lambda. Eg(x)]2

λ - Vacuum wavelength [µm], A, B and C is the empirical coefficient. X= fraction of alloy elements, n - (real part) of the refractive index, Eg= band gap

Refer this paper, https://www.batop.de/information/n_InGaAs.html

Ashish