Direction dependency of extraordinary refraction index in uniaxial   nematic liquid crystals
  The article presents a straightforward experiment that directly and illustratively demonstrates double refraction. For this purpose, two liquid crystalline cells were designed, which enable qualitative and quantitative measurements of the extraordinary refractive index direction dependency in a uniaxial nematic liquid crystal. 
Jerneja Pavlin, Natasa Vaupotic, Mojca Cepic
cond-mat.soft physics.ed-ph