  Reflectometry is a technique that uses the light reflected by a sample to
determine properties of the sample. Interferometric reflectometry uses
interference between two beams, one of which is incident on ---and reflected
back by--- a sample and one of which is not, to obtain the complex electric
field rather than merely its intensity. Since this interference allows one to
retrieve an increased amount of information about the light, it also allows one
to obtain more information about the sample, such as a thin layer. We will
apply the methods derived here to the case of a planar lipid bilayer.
