# How can I estimate the elasto-optic coefficients ($p_{11}$ and $p_{12}$) of a material?

I am attempting to estimate the elasto-optic coefficients ($p_{11}$ and $p_{12}$) of $\mathrm{TiO}_2$ and $\mathrm{ZrO}_2$, where $p_{11}$ and $p_{12}$ refer to the elements of a strain-optic tensor for a homogeneous material as given in Hocker (Fiber-optic sensing of pressure and temperature, 1979).

I have found a document which specifies that the longitudinal elasto-optic coefficient ($p_{12}$) can be estimated using the Lorentz-Lorenz relation that it gives as

$$p_{12} = \frac{(n^2 - 1)(n^2 + 2)}{3n^4}$$

however no reference is given, and other sources give the Lorentz-Lorenz relation as something rather different. For example Wikipedia says that the equation relates the refractive index of a substance to its polarizability and gives it as

$$\frac{n^2 - 1}{n^2 + 2} = \frac{4\pi}{3}N\alpha$$

which bares only a vague relation to the earlier equation.

Does anyone know of any other ways in which to estimate the elasto-optic coefficients of a material?

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Excellent question! Unfortunately I don't know much of anything about optics but I'll see if I can draw some attention to this. –  David Z Aug 22 '12 at 21:03
Thanks - hopefully some insight will be forthcoming soon :) –  user714852 Aug 24 '12 at 17:25