First message here, sorry if this is scrappy:
I am looking to measure the birefringence of multiple crystalline structures (calcite, ice, etc), and came across this methodology:
Shine a laser at normal incidence to the surface of the birefringent crystal. Place a polarising filter between the laser and the birefringent crystal such that only linearly polarised light will reach the crystal. Behind the crystal, place a rotatable polarising filter, and behind that filter, place a sheet of paper. By rotating the 2nd polarising filter, the intensity of the light reaching the sheet of paper should be changing, due to the amount of newly polarised light by the birefringent material changing when the angular displacement of the rotating filter is varied.
By observing the intensity of the light and measuring the angular displacement, the birefringence of the crystal can be found as follows:
with delta n the birefringence, lambda the wavelength of the light, d the thickness of the crystal, and theta the angular displacement.
Is this an accurate way of determining the birefringence of a crystal?
Please let me know if you have any ideas on how to improve this approach.
