# Reflectance of Titanium as Function of Thin Film Thickness

As far as I know, transmittance equals $e^{-\alpha x}$, where $\alpha$ is absorption coefficient and $x$ is thin film thickness($100-300\,nm$). My team and I have engineered a way to find absorption. Transmittance, T= (Output intensity)/(initial intensity). And, absorption A=(initial intensity-output intensity)/(initial intensity). After simplifying the equation, one should get $$A= 1-T$$

The problem I am facing is I do not know any equation, which will give me reflectance of Ti as a function of thin film thickness at $808\,nm$ wavelength. If someone gives me an equation of transmittance, please include the effects of absorption so that I can calculate the reflectance afterwards.

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You can calculate the reflectance in a very similar way to how I calculate the transmittance in this answer. Simply take $E_{out}$ to be the coherent sum of the light reflected back from the 0-1 interface, after any number of round trips through the metal film.
This allows you to calculate $T$ and $R$ independently, and so then you will simply be able to express the absorption as
$$A = 1 - T - R$$